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The role of hard second phases in the mild oxidational wear mechanism of high-speed steel-based materials
Abstract
In the case of dry unlubricated wear of metals, an oxidational wear mechanism can be established under certain conditions, with oxide films being developed on the sliding surface which markedly influence the friction and wear behaviour. For high-speed steel-based materials containing various hard second phases, an a-Fe2O3 film is formed during pin-on-disc testing (under mild conditions of load and sliding speed), which reaches a critical thickness of 1–2 μm before breaking up in loose wear debris. The role of the second phases in the oxidational wear mechanism was studied in this investigation. The size of the hard second phase particles appears to be the most important parameter determining the possibility for the particles to provide protection against oxidational wear of the matrix. Particles of a size less than or equal to the critical thickness are carried away when the oxide breaks up, while particles larger than the critical oxide thickness remain in place. In this case, their ability to protect the metallic matrix from the loads imposed by the counterbody depends on their mechanical resistance to these loads, as well as the strength of their cohesion with the metallic matrix.
... Hard, stable, and continuous MMLs often reduce friction and wear [16][17][18][19]. Pure metals and alloys also form MMLs, but the hard phase present in MMCs is found to play a role in the oxidative wear mechanisms [20,21]. The size and the interfacial bonding strength of the hard reinforcement particles to the matrix influence the critical oxide thickness, which determines the extent of reinforcement particles in providing protection against oxidational wear of the matrix [21,22]. ...
... Pure metals and alloys also form MMLs, but the hard phase present in MMCs is found to play a role in the oxidative wear mechanisms [20,21]. The size and the interfacial bonding strength of the hard reinforcement particles to the matrix influence the critical oxide thickness, which determines the extent of reinforcement particles in providing protection against oxidational wear of the matrix [21,22]. ...
... When the MML is eventually broken down, the reinforcing particles underneath the MML become exposed and reduce metal contacts to the counterbody. At this stage, the load supporting nature of the particles as well as their cohesion strength with the metallic matrix determines their effectiveness on protecting the metallic matrix from wear [20,21]. The critical oxide thickness can be in the range of 1-5 µm for metallic materials. ...
Cold spray is a relatively new method used to deposit WC reinforced composite coatings, where its low temperature is advantageous for avoiding oxidation and carbide decomposition. Previous studies demonstrated that using powders made from agglomerated WC resulted in higher WC retention in a sprayed coating when compared to that of cast WC. However, the influence of the morphology of the starting powders on the coating's microstructure, properties, and wear performance is not well understood. Here, we report cold spray deposition of Ni with two types of WC particles, i.e. cast and agglomerated. In both cases, ~30 vol% WC was retained in coatings, allowing for a side-by-side comparison. Coatings with cast WC featured a multi-modal distribution of WC particles ranging from 0.2 to 20 μm with a mean free path (MFP) between particles of 8.5 ± 0.7 μm. In comparison, coatings with agglomerated WC had WC size range of 0.3 to 1.3 μm and an MFP of 31 ± 4 μm. The sliding wear behavior of coatings was studied with a sliding speed of 3 mm/s under normal loads of 5 and 12 N. Coatings with cast WC were found to be more wear resistant than coatings with agglomerated WC. The multi-modal size distribution of cast WC with significantly lower MFP minimized adhesive wear and helped to develop a higher coverage of protective mechanically mixed layers (MMLs) that typically formed near WC particles. For coatings with cast WC, subsurface microstructure and chemical analysis suggested higher oxidation for MMLs with shallower depths of deformation in the metal matrix beneath the MMLs compared to coatings with agglomerated powder. The main factors for improved wear resistance of cast WC coatings compared to agglomerated WC coatings were the stability of the MMLs, and the wider size distribution with lower MFP, which offered better load supporting properties.
... Studies investigating specifically the influence of the microstructure of HSS alloys on wear behaviour are also still scarce [23,[32][33][34][35][36][37][38]. Notable exceptions are the works by Wang et al. [25] and Tuominen et al. [39] on the resistance of high alloyed laser clad HSS materials with respect to abrasive wear. ...
... For both sliding speeds, oxides formed during the wear test (section 3.5 and section 3.6, particularly Figure 9). Indeed, oxidative wear is the most common tribochemical process [34,[42][43][44]. The contact between sliding surfaces accelerates oxidation, resulting in the formation of a discontinuous oxide layer on the worn surface. ...
... The contact between sliding surfaces accelerates oxidation, resulting in the formation of a discontinuous oxide layer on the worn surface. Oxide islands grow by increasing gradually in thickness, until reaching a 13 This is a pre-print of the paper accepted for publication in Surface and Coatings Technology, doi: 10.1016/j.surfcoat.2017.02.071 critical value at which internal stresses may cause the oxide layer to break [34,45]. As a consequence, depending on the type of these oxides, their presence can either lead to the formation of a protective interlayer, thus decelerating wear [34,45,46] or, on the contrary, it may accelerate wear. ...
The oxidative wear behaviour of four different High Speed Steel (HSS) thick coatings (one cast material and three laser clad deposits with varying Mo, V and W contents) was investigated using a pin-on-disc tribometer at two different sliding speeds of 10 cm/s and 50 cm/s. Microstructural characterization (before and after the wear tests) was carried out by SEM and wear debris was analysed by XRD. For all four materials, the oxide layer was formed of hard and brittle haematite-type α-Fe2O3, prone to break and release debris that acted as a third body, thus increasing sample wear. The laser clad HSS materials exhibited a higher wear resistance than their conventional cast counterpart, thanks to their finer microstructures. In particular, the coarser MC and M2C carbides present in the cast material were sensitive to cracking during the wear tests, releasing debris that contributed to increased third body abrasion together with oxide fragments. A detailed comparison of the wear behaviour of the three laser clad deposits, in correlation with their different microstructures, further demonstrated that harder V-rich MC carbides offered better wear resistance compared to the softer W-rich M2C carbides. The morphology of the carbides also played a role in determining the wear resistance at the higher sliding speed of 50 cm/s. Clover-shaped primary MC carbides resisted wear better than angular ones due to their better geometric anchoring. Similarly, the geometric anchoring of eutectic M2C carbides, forming a quasi-continuous network at the grain boundaries of the matrix, proved beneficial at higher sliding speed.
... The mild-to-severe wear transition of oxidative wear was usually met, snice it is a popular phenomenon under severe wear conditions, but this concept was sparsely mentioned by most of researchers [2,14,15,17,[23][24][25][26][27][28][29][30][31]. Merely a few researcher, such as Garbar et al. [20] and Viáfara et al. [21] mentioned the mild-to-severe wear transition in oxidative wear. ...
... However, these researchers did not realize the existence of the transition region. In practice, their results represented some regularities or phenomena of the transition region [2,14,15,17,[23][24][25][26][27][28][29][30][31]. ...
... Their part results indeed were beyond mild wear and entered into the transition region. In addition, there were other researches touching on the transition region [29][30][31]. ...
Dry sliding tests for steels were performed in air under the test temperature at 400 °C and the loads of 50–250 N. The wear behavior and characteristics were focused on to explore their general characters in severe conditions. The wear behavior of various steels presented a common wear regular pattern; a mild-to-severe wear transition occurred with an increase of the load. Because oxidative wear prevailed, this was suggested to call the mild-to-severe wear transition of oxidative wear. More importantly, a transition region in the oxidative wear was found to exist and corresponded to the different-extent plastic deformation of the subsurface substrate. Through reviewing the past research, the mild-to-severe wear transition of oxidative wear was noticed to be a popular phenomenon in dry sliding wear of severe conditions, particularly elevated-temperature. This transition (region) with oxidative-wear characteristics was considered to the essence of wear failure in severe conditions, which was a physical and chemical process including oxidation, thermally softening and plastic deformation of worn surfaces and subsurfaces. And the wear characteristics in the transition region were revealed.
... However, there are still controversies over the interface adherence between the protective oxide layer and substrate, and the maintenance of such a highly wear resistant film. Some researchers believed that a good match between the metallic and oxide interfaces is mainly responsible for the formation and maintenance of the lubricating film [11,[18][19][20][21], while others advised that it would not be an effective supporter for building up such a layer when the substrate becomes relatively soft [22,23]. Stott and Jordan [24] believed that a high chrome steel substrate with a low hardness can act as a good upholder for establishing an oxide film. ...
... After the tests, the surfaces of each sample are always slightly red, implying the main oxidation product is a-Fe 2 O 3 oxide [7,10]. It was predicted and reported that a-Fe 2 O 3 is the main oxide product when the mean surface temperature is relatively low [7,19,20] (e.g., up to 140 1C predicted by So in 1995 [20]). The relatively low increment of average surface contacting temperature is usually caused by a small load, especially at a low sliding speed [10,13,19,25]. ...
... It was predicted and reported that a-Fe 2 O 3 is the main oxide product when the mean surface temperature is relatively low [7,19,20] (e.g., up to 140 1C predicted by So in 1995 [20]). The relatively low increment of average surface contacting temperature is usually caused by a small load, especially at a low sliding speed [10,13,19,25]. For an un-lubricated system, Rigney suggested that the rise in surface temperature would be limited if a sliding speed of a few mm/s was selected, whereas a sliding speed of m/s would lead to an increase in temperature of hundreds of degrees. ...
Protective oxide film plays an indispensable role in reducing wear during metal-metal sliding contact, and its adherence to the substrate and stability is a major issue. This review examines some prevalent views proposed in literature on the adhesion between protective oxide layer formed during sliding wear and the steels and cast irons substrate under unlubricated condition. Attempt has been made to correlate some of them to be more connected and take them into account in a broader sliding condition in some sections in this review. Although this review is more relevant to the steels and cast irons as the tested materials during unlubricated unidirectional sliding, other alloys such as aluminium and Ni-based alloys would be hopefully to some extent associated.
... The mild-to-severe wear transition of oxidative wear was usually met, snice it is a popular phenomenon under severe wear conditions, but this concept was sparsely mentioned by most of researchers [2,14,15,17,[23][24][25][26][27][28][29][30][31]. Merely a few researcher, such as Garbar et al. [20] and Viáfara et al. [21] mentioned the mild-to-severe wear transition in oxidative wear. ...
... However, these researchers did not realize the existence of the transition region. In practice, their results represented some regularities or phenomena of the transition region [2,14,15,17,[23][24][25][26][27][28][29][30][31]. ...
... Their part results indeed were beyond mild wear and entered into the transition region. In addition, there were other researches touching on the transition region [29][30][31]. ...
Dry sliding wear behaviors of Ti–6Al–4V and Ti–6.5Al–3.5Mo–1.5Zr–0.3Si alloys (code-named TC4 and TC11, respectively) against AISI 52100 steel under a load of 50–250 N at 25–600 °C were systematically investigated. For two titanium alloys, a severe-to-mild wear transition occurred with an increase in temperature. The critical transition temperatures of TC4 and TC11 alloys were 400 and 300 °C, respectively. Below the critical temperature, titanium alloys showed poor wear performance. As the temperature surpassed the critical temperature, the extremely low wear rates demonstrated excellent elevated-temperature wear performance of titanium alloys in the titanium alloy/steel tribo-system. The wear transition was characterized with the appearance of continuous, hard tribo-layer containing more oxides, especially Fe2O3, which showed a pronounced wear-reduced role. Adhesive and abrasive wear predominated in the severe wear regime; oxidative mild wear prevailed in the mild wear regime. Adhesive wear, abrasive wear and oxidative mild wear cooperated at the critical transition temperatures.
... Carbides, if proud enough, may sit above the oxidised layer as to support some degree of the normal load. In particular, Vardavoulias [79] suggested that if the oxide is much more proud than the hard-phase, then it is more likely to fracture off the surface. In the case of non-HIPed processing methods, it may be possible for the carbides to remain more proud than the oxide. ...
... Furthermore, all of the wear debris appears to have a plate-like or lamellar morphology. Though, importantly, this is not always the case, as if the load is sufficiently low oxides may form a protective layer against wear [65] where material degradation may proceed as a fatigue [73] or fracture [79] mechanism. Together, this phenomena could suggest that ratcheting, the incremental increase of shear strain due to cyclic loading, is responsible for the formation of wear particles on a Stellite TM contact. ...
Many sliding applications depend upon cobalt-based hard-facing materials, due to their excellent friction and wear properties, where it is not possible to lubricate the mating surfaces. However, wear produced in such systems present a significant health risk and so there is motivation to understand cobalt-based wear to aid the development of cobalt-free alternatives. The focus of this work is to build a mechanistic model of sliding wear for a given cobalt-based hard-facing alloy. The chosen numerical approach was informed by a series of delineating simple reciprocated sliding wear tests, in accordance with Rolls-Royce research aims, as a stepping stone to more complex environments. Wear testing of a cobalt-based hard-facing alloy, Stellite 6TM, was performed under selfmated reciprocating dry room-temperature conditions. The wear-rate as a function of load was not constant, suggesting a different model of wear than typical linear models of wear. Probing the debrWis morphology, surface topography, and subsurface behaviour of the alloy revealed plate-like particle formation and separation via subsurface material rupture. Unique to this thesis, the sliding wear behaviour for the load range of 400 N to 1000 N was interpreted as belonging to a ratcheting-type wear mechanism. A multiscale model of sliding wear was developed as part of this project. This model incorporates a modified microscale ratcheting wear subroutine into a standard finite element model of sliding wear via statistical homogenisation. This approach is a novel extension to the typical numerical models of sliding wear, and allows the user to see how macroscopic wear is affected as the result of material properties, evolution of surface roughness, or microscale imperfections. The model predicts the correct scale of wear, close to a wear-rate of 1×10−14 m3/Nm. Presently this model only accounts for the purely mechanical aspect of wear, but may be adapted for use in synergetic tribocorrosion models to better understand how Stellite 6TM behaves in a nuclear environment.
... Then, other load-bearing plateau elsewhere on the surface becomes operative as areas of clean metallic surface come into rubbing contact and oxidize. The above description cycle starts again and the oxidative wear mechanism advances [9,10]. This wear mechanism could be operative in a range of service conditions, where low loads and slow velocities are characteristic [11]. ...
... The AW samples showed better wear resistance than PWHT specimens. The reason for this behaviour could be the precipitation of chromium in solution, forming carbides during the heat treatment; thus the metal matrix diminished its chromium content, decreasing the resistance to oxidation of the metal [9,23]. Taking into account that the predominant wear mechanism was mild oxidative, promoted by the test conditions (low load and low speed), the oxidation resistance of the material would have controlled the wear rate while hardness was not determinant [24]. ...
This paper analyzes the effects of post welding heat treatment and applied load in wear tests on the tribological response of hard weld surfacing. The deposit was a martensitic steel obtained with a FCAW metal-cored wire under gas shielding of Ar-2%CO 2 and 2 kJ/mm of heat input. Cross sections were obtained from the welded coupon and subjected at 550°C during 2 hours. These samples, together with the as welded specimens, constituted the system under study. Cross sections were also extracted for both conditions to determine chemical composition, microstructure characterization, micro-hardness measurements in addition to friction and metal-metal wear tests in pure sliding at 500, 1250 and 2000 N of applied load. A microstructure composed of martensite and retained austenite was observed for both conditions. The as welded sample presented 16% of retained austenite whereas the heat treated one 8%. Heat treated coupons showed secondary hardening associated with precipitation phenomena. In the specimens tested at 500 and 1250 N the wear mechanism was oxidative and the as welded specimens presented higher wear resistance and a higher friction coefficient. Regarding the tested samples at 2000 N, wearing mechanism was delamination and heat treated samples resulted more resistant with a higher friction coefficient.
... is not sufficient to assume that their presence will have no effect on the wear process and that they will simply be 'worn way' with the matrix as sliding proceeds; this only occurs if the second phase is of similar or lesser hardness. Vardavoulias [94] studied a number of steels into which hard ceramic phases of various sizes were introduced; these included titanium carbide (modified to a much finer carbon nitride phase by nitrogen annealing), copper phosphide and alumina. It is assumed following that the substrate metal is oxidised and is the main source of compacted oxide or oxide debris and, thus, the oxide / metal interface is effectively moving into the metal. ...
... and Nimonic 80A, comparisons with the studies of Vardavoulias [94] indicates that the second phase in each case is too small to affect the 'glaze' forming process. ...
A review of high temperature tribocorrosion is presented focusing attention on those contributions that illustrate the general principles, modeling, and scientific theories of the processes of high temperature wear. A significant aspect of this chapter is the inclusion of new information on glaze formation, generated at the sub-microscopic and nano-scale level. .
... Compared with the conventional wear-resistant steels SKH51 and SUJ2, Al00Ti10 and Al02Ti10 exhibit even higher resistance to adhesive wear. The wear resistance of SKH51 and SUJ2 originates from their hard carbide phases [44][45][46]. Similarly, the hard g phase in Ti10 alloys should also be an important factor in their anti-wear properties. ...
... Similarly, the hard g phase in Ti10 alloys should also be an important factor in their anti-wear properties. However, the carbides in SKH51 and SUJ2 are harder than the g phases in Ti10 alloys [45]. Therefore, some other factors must also play important roles in the wear of Ti10 alloys. ...
A series of AlxCo1.5CrFeNi1.5Tiy high-entropy alloys with different Al and Ti contents were designed, and their phase and microstructure were investigated. The adhesive wear behavior and mechanism were also studied and compared with the conventional wear-resistant steels SUJ2 and SKH51. The amounts of Al and Ti strongly affect the phase and microstructure, particularly the amount and morphology of the hard η-(Ni, Co)3Ti phase. It was found that the wear resistance of the Co1.5CrFeNi1.5Ti and Al0.2Co1.5CrFeNi1.5Ti alloys is at least two times better than that of conventional wear-resistant steels with similar hardness. The excellent anti-oxidation property and resistance to thermal softening in these high-entropy alloys are proposed to be the main reasons for the outstanding wear resistance.
... Carbides protruding above the surface of the matrix can temporarily protect it from further wear and tear. This protection occurs because the protruding carbides prevent direct contact between the sample surface and the sandpaper [12,25]. The protruding carbides can provide anchor points for wear residues, favoring their compaction and thus a stable protective coating is obtained [11,26,27]. ...
Hardfacing of Ni and Co-based alloys has been widely applied to extend the lifespan of components that operating under severe conditions. The recent development of computational tools, such as Scorpeta from Oerlikon Metco, has allowed the design of alloys with customized properties. Metco 1040® (Fe-V-Mn-C) is a novel hardfacing alloy designed by the Scorpeta process to improve the abrasion and impact resistance of manganese steel substrates. However, few authors have addressed its wear performance. Therefore, the purpose of this study was to evaluate the effect of the processing parameters on the microstructure and wear resistance of the Metco 1040® alloy deposited by laser cladding on Hadfield steel. Single beads were deposited on Hadfield steel substrates according to a full factorial design of experiment (DOE), in which the laser power and deposition scanning speed were varied with 3 levels (3²). Using some selected parameters, areas were covered by depositing parallel beads with an overlap of 30%, aimed at assessing the wear resistance through the “pin on drum” test. On applying the response surface method, it was found that the observed effects of the processing parameters (laser power and scanning speed) on the bead geometry (height, width and dilution) corroborate the current literature. For a given scanning speed, the higher the laser power the larger the carbide size and interdendritic spacing will be. The deposition parameters had no significant effect on the hardness or wear resistance of the coatings. However, the coating performance was significantly higher than that of Hadfield steel substrate. The findings reported herein suggest that the Metco 1040 alloy can be used to extend the lifespan of components of Hadfield steel.
... Carbides located above the matrix surface can temporarily protect it from further wear. This protection occurs because the protruding carbides prevent direct contact between the sample surface and the sandpaper [31]. The protruding carbides can provide anchoring points for wear debris, favoring their compacting and sintering, obtaining the formation of a stable protective tribocoat [32,33]. ...
The premature wear and/or failure of components and equipment used for ore comminution can result in unscheduled downtime and, therefore, significant losses for the mining industry, in which it is estimated that about half of the total maintenance cost in mining is due to the manufacture of damaged parts and the other half due to downtime and labor. In this sense, approaches to improve the wear resistance of this kind of equipment are of great interest. Therefore, the present work aims to evaluate the potential of coating a high manganese Hadfield steel used to manufacture grinding hammers with Metco 1030A alloy (Fe–C–Mo–V–B) via laser cladding (DED-L). The coatings were deposited on Hadfield steel substrates (cast) using different levels of laser power and scanning speed. The coatings were characterized in relation to the presence of surface and internal defects, morphology, microstructure, chemical composition, and microhardness. The wear resistance of the coatings was evaluated by pin-on-drum tests. For all deposition conditions, continuous tracks were formed. Despite the superficial cracks, the layers did not detach, confirming the metallurgical bond with the substrate. The microstructure of the coatings is typically composed of vanadium carbides (VCs) and molybdenum borides (Mo2B) in a martensitic matrix. For the same scanning speed, carbides and borides tend to become larger and more widely spaced with increasing laser power. Compared with the Hadfield steel substrate, the coatings have significantly higher hardness and wear resistance. Despite the cracks, normally acceptable in the intended application, it can be said that the application of the Metco 1030 alloy via laser cladding has the potential to increase the service life of Hadfield grinding hammers.
... This is because, during the testing period, there appears some black fine powder between the rubbing surfaces that indicates the formation of an oxide film and the wear mechanism changes from adhesive wear to reduced abrasive wear. Wang et al. [34] and Vardavoulias [35] have also observed similar results. The variation in COF with normal load and sliding speed is shown in Fig. 6(b). ...
In this study, specific wear rate (SWR) and coefficient of friction (COF) of the synthesized samples in 55[(Pb x Ca 1−x)O.TiO 2 ]−44[2SiO 2 .B 2 O 3 ]−1Ge with (0 ≤ x ≤ 0.7 mol%) system of glass ceramics was optimized using Taguchi method. The ASTM standards were used for preparing the samples for friction and wear tests on a pin-on-disc tribometer. The glass ceramic samples were used as pin materials that slid against a disc made up of EN32 steel. For assessing the tribological properties of the glass ceramics, three control factors, viz. material-compositions with varying fraction of x (x = 0.0, 0.1, 0.3, 0.5 and 0.7 mol%), sliding speeds (2.61, 3.14, 3.66, 4.18 and 4.71 m/s) and loads (10, 15, 20, 25 and 30 N) were considered in an L 25 orthogonal array design. The optimum input parameters for the minimum SWR and COF were selected based on signal to noise ratios and main effect plots. Analysis of variance (ANOVA) revealed that the sliding speed and lead oxide content of the material are the most contributing factors on SWR and COF, respectively. The optimization for minimizing the SWR and COF was carried out and confirmed. The surface morphologies of the tested glass ceramic sample were studied using scanning electron microscope (SEM) and the elemental analysis of the samples was done using energy dispersive analysis of X-rays (EDAX). The Vickers hardness at the free surface of the glass ceramic samples increased up to 9.59 mol% of lead oxide with the maximum hardness of 23.59 GPa. The compressive strength of glass ceramic samples could reach up to 190 MPa.
... The physical characteristics like porosity, second phase reinforcement, near surface microstructure of a bulk or coating material significantly influence its friction and wear behaviour [11,27,28]. ...
Ti6Al4V coatings were made from spherical and irregular powders manufactured using plasma gas atomization and Armstrong processes, respectively. The coatings, made from the two different powders, were distinctly different in terms of porosity content and hardness. Sliding wear tests were performed at different normal loads on both Ti6Al4V coatings. Despite low porosity and high hardness, irregular powder (IP) deposited coatings showed higher wear rates compared to spherical powder (SP) deposited coatings. In case of IP coatings, abrasive ploughing by the wear debris led to high wear rates whereas presence of porosity in SP coatings, entrapped the wear debris generated during sliding and decreased the wear rate. Increase in normal load led to a decrease in wear rate and CoF in both coatings. The decrease in wear rate was due to tribo-oxidation in IP coatings whereas the combined effect of entrapment of debris along with tribo-oxidation resulted in much lower wear rates in SP coatings. Transmission electron microscopy (TEM) analysis showed that the third bodies filled in the pores consisted of highly deformed material with ultrafine grain microstructure and micron sized particles from the counterface while the wear track had comparatively coarse grain microstructure. Results indicated that despite low hardness of SP Ti6Al4V coatings, presence of porosity facilitated for the entrapment of wear debris generated from first bodies which inhibited abrasive ploughing and contributed to low wear rates.
... The wear rate decreases with increasing normal load and counter-body sliding speed but remains constant with the sliding distance increase. The wear rate reduction with normal load (Fig. 5a) results from the increasing in the contact area, promoting decreasing of contact pressure [21,22]. As a result, material removal rate by grooving and rolling effects promoted by abrasive particles is minimized. ...
... The higher wear resistance of GCr15 at RT is ascribed to the hard carbide phase [37,38]. Nevertheless, the carbide phase is easily decomposed at high temperature, resulting in rapid decrease in the hardness of the GCr15 (seen in Fig. 6). ...
The microstructure, hot hardness and oxidation behavior of Al0.6CoCrFeNi high-entropy alloy were investigated. Moreover, the effect of the temperature on the tribological properties of Al0.6CoCrFeNi high-entropy alloy was studied. The results showed that the σ-CrFe phase was precipitated after heat treatment. The hardness of HEAs increased from 278 to 480 HV. The HEAs possessed higher wear resistance than that of the conventional alloys at elevated temperatures. The wear resistance of annealed alloy was nearly 3 times higher than that of GCr15 steel at 600 °C. With increasing temperature, the predominant wear mechanism was transformed from the abrasive wear to the mild oxidative wear as well as delamination wear with increasing the temperature.
... This is because, during the testing period, there appears some black fine powder between the rubbing surfaces that indicates the formation of an oxide film and the wear mechanism changes from adhesive wear to reduced abrasive wear. Wang et al. [34] and Vardavoulias [35] have also observed similar results. The variation in COF with normal load and sliding speed is shown in Fig. 6(b). ...
In this study, specific wear rate (SWR) and coefficient of friction (COF) of the synthesized samples in 55[(PbxCa1-x)O.TiO2]-44[2SiO2.B2O3]-1Ge with (0 ≤ x ≤ 0.7mol%) system of glass ceramics was optimized using Taguchi method. The ASTM standards were used for preparing the samples for friction and wear tests on a pin-on-disc tribometer. The glass ceramic samples were used as pin materials that slid against a disc made up of EN32 steel. For assessing the tribological properties of the glass ceramics, three control factors, viz. material-compositions with varying fraction of x (x = 0.0, 0.1, 0.3, 0.5 and 0.7mol%), sliding speeds (2.61, 3.14, 3.66, 4.18 and 4.71m/s) and loads (10, 15, 20, 25 and 30N) were considered in an L25 orthogonal array design. The optimum input parameters for the minimum SWR and COF were selected based on signal to noise ratios and main effect plots. Analysis of variance (ANOVA) revealed that the sliding speed and lead oxide content of the material are the most contributing factors on SWR and COF, respectively. The optimization for minimizing the SWR and COF was carried out and confirmed. The surface morphologies of the tested glass ceramic sample were studied using scanning electron microscope (SEM) and the elemental analysis of the samples was done using energy dispersive analysis of X-rays (EDAX). The Vickers hardness at the free surface of the glass ceramic samples increased up to 9.59mol% of lead oxide with the maximum hardness of 23.59GPa. The compressive strength of glass ceramic samples could reach up to 190MPa.
... It has been observed that the COF varies in the range of 0.3 to 0.55 for a load of 10 N and 0.17 to 0.5 for a load of 20 N. The COF of all the glass ceramic samples decreases with an increase in applied load. This may be due to the formation of the protective layer at high loads by the compaction of the loose wear debris inhibiting the contact between the mating surfaces [22,24]. The COF decreases with an increase in bismuth content which may be due to the good binding nature of bismuth at microstructure level. ...
Glass ceramic samples of five different compositions were prepared in the systems 60[(Sr1-xBix).TiO3] - 39[2SiO2.B2O3] -
1[CeO2] (x = 0.0, 0.1, 0.2 and 0.4 mole %) and 60[(Sr1-xBix)TiO3]-40[2SiO2.B2O3] for x=0.1 mole% by employing conventional
melt quench technique. This paper presents the tribological study, viz. specific wear rate and coefficient of friction, of the
synthesized borosilicate glass ceramics at different applied normal loads under dry conditions using a pin-on-disc tribometer. It
has been observed that the strontium bismuth titanate borosilicate glass ceramic sample with higher bismuth content shows
reduced wear rate compared to other samples. Also, the coefficient of friction decreases with an increase in bismuth content. This
may be due to good binding nature of bismuth at the microstructure level. The morphology and the wear mechanism of the worn
out surfaces of different glass ceramic samples were also studied using scanning electron microscope (SEM).
... Therefore some PM steels with high sintered density as well as high wear resistance have found wide application in the automotive industry, in engine and transmission systems, mainly for wear loaded components such as gears, sprockets and cam lobes [2,3]. However, the wear behaviour research has been relatively scarce compared to steels manufactured by other routes [4][5][6][7][8]. ...
In this work, the hardness and abrasive-wear be-haviour of powder metallurgy (PM) plain carbon steel and microalloyed steels with different amount of niobium or aluminium content (0.1-02 wt.-%) were investigated. It was found that steels microalloyed by niobium and alumin-ium have high hardness and wear resistance compared with the niobium and aluminium free steel. Wear behavior of these steels depends on the PM processing parameters and wear conditions. Worn surface pattern revealed the wear mechanism is ploughing. The surface exhibited extensive grooving occured as a result of ploughing by the harder SiC paper.
... Stoff [5] showed that segmented tribofilm can be as efficient against wear as a continuous film, which may explain lower values of friction coefficient (and high performance shown in such wear condition. According to Vardavoulias [6], this random distribution of tribofilm may be associated with the presence of carbides that act as anchoring regions for the tribofilm. For the samples treated at 450°C for different times, the morphology and main wear mechanisms were similar to those shown in Figure 2, so micrographs are not presented. ...
The dry sliding wear behavior of the low-temperature plasma carburized AISI 420 steel was studied, at room temperature, using ball-on-disk tribometer (6.0mm Al 2 O 3 ball; normal load: 5N; sliding distance: 1000m; sliding rate: 0.05ms-1). Specimens were treated for 8h, at temperatures ranging from 350 to 500°C. Additional treatments were performed at constant temperature of 450°C for 4, 8, 12 and 16h. XRD, microstructural analysis, and hardness measurements were applied as characterization techniques. Results showed that the wear coefficient decreases when the treatment temperature varies from 350 to 450°C. In contrast, it increases for 500°C. For samples treated at 450°C, the wear coefficient behavior is characterized by an inverted bell curve with a minimum for 12h. This behavior was attributed to the transition from the carbon in solution, in the carbon-expanded martensite, to the carbon present in the precipitated carbides. Finally, the analysis of the wear tracks indicates the occurrence of abrasion wear and tribofilm formation.
... There were many fine and large-sized carbides in the subsurface matrix of the SDCM-S steel. The hard second phase particles are the most important parameter for determining the wear resistance of the steel at low temperature, and can protect the matrix against wear [44]. With regard to oxidative wear, the function of the carbides depends on their influence on the matrix. ...
The friction and wear characteristics of new Mo-W-type hot-work die steel, known as SDCM-S, were studied at high temperature. The results showed that the new Mo-W-type steel had greater wear resistance compared with H13 steel, which was due to its high oxidizability and high-temperature property. The high oxidizability and high temper stability features facilitate the generation, growth, and maintenance of a tribo-oxide layer at high temperature under relatively stable conditions. The thick tribo-oxide layer and high temper stability postpone the transition from mild to severe wear and ensure that conditions of mild oxidative wear are maintained in SDCM-S steel. The M2C and M6C carbides in Mo-W-type steel increase the temper stability and provide sufficient additional support for the formation and growth of a single thick tribo-oxide layer at high temperature. Mild oxidative wear is the dominant wear mechanism for SDCM-S steel between 400 and 700 °C.
... In accordance with practice the particle was assumed to have a diameter 10 µm. This is an agreement with the size of primary M C and MC carbide particles reported by Vardavoulias (1994) where the particles vary between 2 and 10 µm. The assumptions and parameters used in the FE modelling are summarised in Table 1. ...
... Aşınma direnci sert partiküllerin miktarına, boyutuna, dağılımına ve matris ile takviye elemanlarının sertliğine ve kırılma tokluğuna bağlıdır [5]. Bileşenler arasında mekanik bağlanmanın yanısıra, kimyasal bağlanmanın da olması mukavemeti artırır [6]. Mikroyapı içerisindeki karbür ile malzemenin diğer bileşenleri arasındaki ilişki ve aşınma davranışı ile ilgili birçok çalışma yapılmıştır [7]. ...
... To monitor this wear test process, some black fine powders could be observed between the rubbing surfaces during rubbing process. The phenomenon indicates that oxide films are being developed on the rubbing surfaces to change wear mechanism into oxidation wear and avoid adhesive wear and reduce abrasive wear [12]. ...
This work deals with the wear performance of clad layers, which clad WC and TiC powders on medium carbon steel by gas tungsten arc welding (GTAW) method. Various metal powders with equal percentage by weight were added to the base powder (WC, TiC) to prepare the cladding materials, which were used to study the effects of various ceramic–metal cladding materials on clad surface wear resistance ability. A rotating type tribometer was used to evaluate the wear behaviors of different cladding specimens under dry sliding conditions. According to the experimental results, the specimen clad by WC-based powder contains certain Ti metal powders which had the best wear performance in all WC clad specimens. In all TiC cladding specimens, the TiC with W clad layer had superior wear performance to the other cladding specimens under low sliding speed condition. On the contrary, the TiC with Cu clad layer was superior to the other cladding specimens under high sliding speed condition. In addition, oxide films influence the wear behaviors of different specimens during wear testing, and at some conditions oxidation wear would dominate the wear behaviors of clad layer.
... This might be associated with the fact that during heat treatment, the chromium in the solution precipitated, forming carbides and therefore reducing the matrix resistance to oxidisation. 17,18 Oxide islands were found in worn surfaces of these samples, as can be seen in Figure F7 7a. Figure 7b shows EDS performed on zone A (oxide presence was confirmed by the EDS study). Abrasion lines, with orientation parallel to the sliding direction, were seen on the worn surfaces. ...
This paper analyses the effects of post-welding heat treatment on the tribological response of weld metals for hardfacing. Applied load in wear tests was also studied. The deposit was a martensitic steel obtained with a gas metal arc welding metal-cored wire under gas shielding of Ar–2% CO2 and 2 kJ mm−1 of heat input. Cross sections were obtained from the welded coupon and subjected at 550°C for 2 h. These samples, together with the as-welded (AW) specimens, constituted the system under study. Cross sections were also extracted for both conditions for determination of chemical composition, microstructure characterisation, microhardness measurements in addition to friction and metal–metal wear tests in pure sliding at 500, 1250 and 2000 N of applied load. A microstructure composed of martensite and retained austenite was observed for both conditions. The AW sample presented 16% of retained austenite, whereas the heat-treated one presented 8%. Heat-treated coupons showed secondary hardening associated with precipitation phenomena. In the specimens tested at 500 and 1250 N, the wear mechanism was oxidative and the AW specimens presented higher wear resistance and higher friction coefficient. On the contrary, the wear regimen of the samples tested at 2000 N was severe, with the heat-treated ones more wear resistant with a higher friction coefficient. Copyright © 2012 John Wiley & Sons, Ltd.
Chromium carbide-based coatings have commonly been used for tribological applications due to their hardness, improved corrosion, and oxidation resistance in harsh environments. This study focuses on the influence of deposition processes (i.e., APS and HVAF) and binder content (i.e., pure carbide versus cemented carbide) on the coatings microstructure, mechanical, and tribological properties at room temperature (RT) and 450 °C. Microstructural analysis revealed that both APS and HVAF coatings had a uniform and dense structure, while the APS coatings showed higher porosity and lower Cr3C2 content due to carbide dissolution, decarburization, and oxidation. The tribological tests showed that APS-sprayed Cr3C2 coating (high power condition) had the highest friction and wear rate, possibly due to their high porosity and brittle nature. The HVAF-sprayed Cr3C2-25NiCr coatings produced by 4L4 nozzle showed the lowest friction and wear loss at both temperatures (room temperature and 450 °C).
High-temperature wear tests on molybdenum–tungsten–vanadium steel were conducted using a universal mechanical high-temperature friction and wear testing machine. The experimental results reveal the evolutionary mechanism of high-temperature friction in the oxide layer of the steel. The oxidation wear of the test steel occurred at 700 °C with the evolution of characteristic monolayer tribo-oxidation layers on the frictional surface. The frictional oxide underwent oxide initiation - lateral growth of massive oxide - formation of frictional oxide layer - local intrusion of oxide layer into substrate - local penetration of oxide lateral growth contact. The frictional oxide evolutionary process was accompanied by a shedding of the frictional oxide surface. Carbides in the test steel prevented the tribo-oxidation layer from invading the matrix. The unique evolutionary characteristics of the tribo-oxidation layer are essential factors affecting the mechanism of maintaining slight oxidative wear.
Plasma carburizing has emerged as a potent technique for improving the wear resistance of stainless steels, and sustaining or improving corrosion resistance through a suitable choice of process parameters. This study evaluated the impact of plasma carburizing time and temperature on the tribological behavior of AISI 420 martensitic stainless steel through dry-sliding wear tests in a ball-on-disk configuration. Two different treatment sets were conducted to assess the impact of carburizing time and temperature on the wear performance of the treated AISI 420 steel. The first group encompassed treatments at temperatures spanning from 350 to 500 °C, with fixed treatment times of 8 and 12 h. The second group involved treatments at a temperature of 400 °C for durations spanning 12 to 48 h and at temperature of 450 °C for durations between 4 and 16 h. To facilitate the discussion of wear test results, microstructural analysis was performed using metallographic analysis, X-ray diffraction, and microscale hardness measurements. Microstructural characterization results revealed that the carburized surface consists of an outer layer followed by a diffusion layer. The diffusion layer is primarily composed of the α′C phase, while the outer layer contains α′C and Fe3C (for low-temperature and short-time treatments) and Cr/Fe-carbides primarily formed due to the α′C decomposition into Fe–α phase (for the studied higher-temperature and longer-time treatments). Wear test results suggest that the surface structure and composition of the treated material exert substantial influence on its tribological behavior. Carburized layers free from Cr-carbide precipitation exhibit lower wear and friction coefficients. The decomposition of α′C into Fe-α and Cr/Fe-carbides leads to an elevation of friction and wear coefficients. Finally, carbon enrichment does not alter the wear mechanism, as both uncarburized and carburized samples exhibited microabrasion and oxidative wear.
Finding the correlation among manufacturing process, microstructure and mechanical properties is critical to design the high-performance alloy. In this study, room temperature ball-on-flat dry sliding wear behavior of carbide-reinforced Ni-Co-Cr-Mo-Cu alloys prepared by hot isostatic pressing (HIP) and hot extrusion (HEX) against Al2O3 ball were investigated. Carbides in the HIP alloy are fine, nearly spherical and have a higher area fraction, in comparison with HEX alloy. Abrasive wear dominates under 10 N load condition, large-sized carbides in HEX alloy display a better resistance to HIP alloy. Oxidative wear dominates under 30 and 50 N load condition, the nearly spherical carbides in the HIP alloy form a stable mixed glaze layer with the fully oxidized alloy surface, lower coefficient of friction (COF) and wear rate were obtained in comparison with HEX alloy. The significant decrease in the wear rate of Al2O3 against HIP alloys under 30 and 50 N load condition is due to the lubricating effect of the oxide glaze layer. The wear rate of the Al2O3 against the HEX alloys almost unchanged due to the insufficient lubrication. It is speculated that the absence of the glaze layer in the HEX alloy is due to the irregular shape of its carbides.
In 18Ni300 maraging steel (MS) prepared by laser metal deposition (LMD), Ni3Al intermetallic compound is precipitated due to intrinsic heat treatment (IHT). Precipitation strengthening of the samples by IHT without further heat treatment is a prospective way to boost the mechanical behaviors of MS. The properties of the samples are represented by field emission scanning electron microscopy (FSEM), hardness measurement, tribological test, and potentiodynamic polarization test. The results indicate that these specimens are constituted by massive martensite, slight retained austenite, and intermetallic compounds. The hardness of the sample increases by 202 HV with the addition of Al. When the 6 at% atom Al is added, the sample with relatively good wear and corrosion resistance was obtained. When the Al concentration is 12%, the microstructure evolves from the equiaxed dendrite structure to coarse-grained martensite, which brings about the reduction of the mechanical properties of MS + 12 at.% Al.Graphical abstract
Despite many studies on the subject, brake squeal remains a major concern for the automotive industry. Much progress was made toward understanding and preventing this issue, focusing on the dynamic behavior of the brake. However, the problem is far from fully understood. Among many friction material ingredients, abrasives are extensively used to regulate friction and wear and are recognized as the main contributors to brake noise. This work investigates the correlation between characteristics of abrasives and squeal noise occurrence determined through the SAE J2521 dynamometer test procedure, FESEM, EDS, nanoindentation, and roughness profiling analyses. The particle size, hardness, Young's modulus, and resistance to elastic deformation of 13 different grades of abrasives were measured. The correlation between these characteristics and squeal noise occurrence was determined through statistical analysis. Spearman's rank correlation coefficient (ρ) showed that squeal noise strongly correlated with hardness and resistance to elastic deformation (ρ = 0.61 and ρ = 0.56, respectively) of abrasive materials and exhibited a poor correlation with their particle size (ρ = −0.099). However, considering groups of samples of the abrasive type, particle size is a characteristic that should be regarded in analyzing squeal noise propensity. In the case of SiC, coarser particles (D90 = 196.70 μm) showed a significant reduction in squeal noise compared to finer particles (D90 = 6.30 μm). On the other hand, coarse particles markedly increased the mass loss of the brake pad and brake disk.
This study developed a series of Alx(TiZrHfNb)100-x (x = 0, 3, 5, 7, 12 at. %) refractory high-entropy alloys (RHEAs) with an aim to improve the poor oxidation and wear resistance at elevated temperature of the base alloy TiZrHfNb. These alloys were prepared by arc melting, and the mechanical properties, oxidation and wear resistance at elevated temperatures were studied systematically. The results indicate that all the alloys are single solid solution phase with body-centered cubic (BCC) structure. The addition of Al significantly improves the strength of the RHEAs due to the large solid solution strengthening effect, and the yield strength and Al content obey the liner relation. The oxidation and wear test results indicate that the Al element will preferentially react with O atoms and accumulate on the surface to form a dense oxide layer, which prevents other elements reacting with O atoms and makes the alloy have better oxidation resistance at high temperatures, especially in alloys with 12% Al. The friction coefficient and wear rate of the RHEAs dramatically decrease with the increase of Al, which can be attributed to the combined effect of mechanical properties and oxidation resistance. This study provides an effective method for improving the oxidation resistance and wear resistance of RHEAs in a relatively high temperature range.
New approaches to improving wear resistance with an affordable and noncomplex technology, such as deep cryogenic treatment, (DCT0), are receiving attention. The aim of this study is to investigate the effect of DCT on the friction and wear performance of high-speed steels. AISI M2, AISI M3:2 and AISI M35 were heat-treated under different conditions, and then investigated under dry sliding conditions. Tribological testing involved different contact conditions, prevailing wear mechanisms and loading conditions. The DCT effect on sliding wear resistance depends on HSS steel grade, as well as contact conditions and wear mode, whereas it improves the dynamic impact of the wear and galling resistance.
A novel high hardness Fe-based composite coating reinforced by M3(C, B) carboboride was prepared by laser cladding. The microstructure and solidification process of the coatings were characterized. The residual stress distribution of the coating was studied. The wear resistance of the coating was tested, and the wear mechanism of the coating was analyzed in detail. The results showed that the microstructure of the coating was martensite with nano-twin, M3(C, B) carboboride precipitated along the grain boundary, and block carbide located therein the matrix. Due to the synergistic effect of thermal stress and phase transformation stress, the residual stress distribution of the coating was compressive stress, and the interface between the coating and substrate was low residual tensile stress, which was beneficial for reducing the risk of cracking from the coating. The average hardness of the coating was over 850 HV, which was 2.5 times than that of the 42CrMo substrate (335 HV), and the wear resistance of the coating was 0.92×10⁻⁵ mm³/N·m, which was 98.3% lower than that of the 42CrMo substrate (54.7×10⁻⁵ mm³/N·m), indicating the very high hardness and excellent wear resistance of the coating.
A series of TiZrV0.5Nb0.5Alx refractory high entropy alloys were prepared by arc-metling, aiming to solve the problems of high density, poor oxidation and wear resistance of refractory high entropy alloys at elevated temperature. The microstructure, mechanical and tribological properties were investigated. The results indicate that the increase in Al addition could promote precipitation of Laves phase in the BCC matrix, thus regulation the mechanical properties. The tribology behavior is strongly dependent on the temperature. Below 400 °C, the wear mechanism is dominated by mechanical wear. In this case, the TiZrV0.5Nb0.5Al0.25 alloy with high strength and good ductility at the same time, exhibits optimal wear resistance. When the temperature increases above to 600 °C, the coefficient of friction and the corresponding wear rate dramatically decrease with Al addition, which could be attributed to the preformed formation of dense and stable oxide glazed-layer before wear. Accordingly, the main wear mechanism changes from mechanical wear to oxidation wear. This study provides an effective strategy for improving wear resistance and oxidation resistance of refractory high entropy alloys in a wide temperature range.
Ni-SiC composite coatings were successfully deposited on interior surfaces of cylinders by circulating-solution electrodeposition (CSD) technique on a newly-designed composite electroplating apparatus. The circulating-solution agitation was effective to improve the dispersibility of SiC particles. The morphology, microstructure, hardness and tribological performances of Ni-SiC composite coatings varying SiC content were studied. Results showed that the dominant wear mechamism was oxidative wear, accompanied by abrasive wear. The friction coefficient and wear rate decreased with increasing SiC content. The excellent wear resistance was attributed to the existence of (111) growth twins, the improved hardness, the protections from NiO layer and SiC reinforcements, and the friction-induced microstructure changes underneath the tribo-surface. The protective capability of NiO layer and micro-SiC particles were discussed in detail.
Ti6Al4V-TiC metal matrix composite (MMC) coatings were cold sprayed using spherical and irregular Ti6Al4V powders manufactured with plasma gas atomization and the Armstrong process, respectively. Composite coatings deposited using irregular powders showed higher ceramic retentions and lower porosity compared to spherical powders coatings. Sliding wear tests were performed at two different normal loads using a spherical WC-Co ball as counterface. Wear test results showed that at similar ceramic contents, spherical powder (SP) composites exhibited abrasive wear mechanisms with high coefficients of friction (CoF) and wear rates. In irregular powder (IP) composites, islands of tribolayers, comprised of fragmented TiC and TiO2 particles, resisted the localized shear deformation leading to low wear, and with free carbon from the TiC particles also lowered the CoF. Increase in ceramic content in the IP MMCs to 23% led to higher coverage of wear track area with tribolayers and further lowered the wear rate. At higher load, 23% TiC composite coatings showed a more continuous tribolayer, whereas lower ceramic content MMCs showed no significant formation of tribolayers. The formation of a highly continuous tribolayer at higher load (in 23% TiC MMC), led to extremely low CoF (~ 0.25) compared to other coatings along with low wear rate. Electron channel contrast imaging and transmission electron microscopy analysis of the worn subsurface under the tribolayers showed coarse-grain microstructures compared to the bare regions of the wear track (i.e. without tribolayer coverage). The formation of coarser grain microstructures indicated less stress transfer to the subsurface both due to the high hardness and lubricating nature of the tribolayers.
This work studies the influence of oil-water ratio on the wear behavior of casing lubricated with drilling fluid using a pin-on-disc tribometer. The disc samples and pin samples are made of Cr13 steel and G105 steel, respectively. Three-dimensional profiles, SEM images and cross-sectional images were used to observe the wear morphology. The XRD and polarization curves analyses were employed to analyze the wear mechanisms under different oil-water ratios. Results showed that the addition of diesel oil into drilling fluid can significantly reduce casing wear. The wear rate and mean friction coefficient decrease first as oil-water ratio increases from 0 to 3 and then increase when oil-water ratio continues to increases from 3 to 5. Exorbitant oil content prevents the loss of friction heat, resulting rapid rise in drilling fluid temperature and significant improvement of Cl- activity. Therefore, the corrosion rate is increased and the corrosive wear dominates the wear process as oil-water ratio increases from 3 to 5. The main wear mechanism of casing lubricated with drilling fluid is abrasive-corrosive wear, and the dominant wear type is abrasive wear when the oil-water ratio is 0 to 2 while corrosive wear when the oil-water ratio is 3-5. During drilling, on the premise of meeting drilling requirements, controlling the oil-water ratio of drilling fluid to about 3 can effectively reduce the wear of Cr13 steel casing.
In this study, Inconel 718 coatings were fabricated by high pressure cold spray deposition and the microstructure and tribological properties of the coatings were systematically investigated at both room and elevated temperatures. At the first place, the investigation on the effect of thermal exposure on the surface oxidation of the coatings was conducted in the absence of sliding. It was found that oxides started to form on the coating surface when the ambient temperature was above 500 °C. At 600 °C, a NiFe2O4 spinel oxide layer spread over the coating surface. Under sliding against an Al2O3 counter ball, oxides started to form on the coating surfaces in contact with the ball when the ambient temperature was above 200 °C due to the fact that the frictional and external heat had facilitated the formation of the oxides. Thus, the friction coefficients of the Inconel 718 coatings decreased with the increase of ambient temperatures. However, the wear rates of the coatings increased at 100 °C and 200 °C compared to those of the coatings tested at room temperature, which was due to the decrease of hardness and severe abrasive wear. When the ambient temperature was further increased to 300 °C, a transition in wear mechanism occurred and the wear rates decreased due to the formation and breakage of the surface oxides that could act as lubricants between the counter ball and coating. With further increase of ambient temperature, a ‘glaze’ layer was formed and grew on the wear tracks, which could act as a protective layer and showed a load-bearing effect that prevented further removal of the coating materials, resulting in an improved wear resistance of the Inconel 718 coatings at elevated temperatures. Therefore, cold sprayed Inconel 718 coatings could be potentially used under wear conditions at elevated temperatures.
Tensile residual stress in the laser-deposited M4 fabricated by direct energy deposition (DED) may reduce the fatigue performance and tool life. Ultrasonic nanocrystal surface modification (UNSM) can induce compressive residual stress by generating severe plastic deformation of the material surface, and improve the wear resistance through surface texture refinement. In the present study, we investigated the changes in the metallurgical and mechanical properties of DEDed M4 specimens as induced by UNSM treatment. An X-ray diffraction analysis showed that the DEDed M4 austenite was transformed into martensite after UNSM processing. The change in the full width at half maximum revealed a grain size decrease of 25.8%. Conversion of the tensile residual stress within the DEDed M4 to compressive residual stress through UNSM treatment was confirmed. These changes in the metallurgical characteristics yield a 24.1% increase in the DEDed M4 hardness. A wear test was conducted to evaluate the wear resistances of heat-treated D2, DEDed M4 on D2, and UNSM-DEDed specimens. Ball-on-disk wear tests revealed that the DEDed M4 specimen wear rate was 68.3% lower than that of the H-D2. In addition, the DEDed M4 wear rate was reduced by 85.7% through UNSM treatment. The surface roughness was reduced by up to 88.3%, while micro-dimple shapes were formed on the DED-treated M4 surface. This study has demonstrated that UNSM can be applied to a DED-treated M4 surface to enhance its metallic and mechanical properties.
A low-carbon steel sheet with a thickness of 5 mm was subjected to friction stir processing (FSP) by one to four different passes. The microstructures of different regions were characterized using the optical microscopy and electron backscatter diffraction. The Vickers micro-harness was measured at the distance of 200 μm below the processed surfaces. The influence of pass numbers (PNs) on wear resistance was studied in terms of coefficients of friction (CoFs), weight losses and wear rates. SEM topographies of the worn surfaces were also studied to evaluate the wear mechanisms. Microstructure observations showed that Widmänstatten ferrite plates were formed in stir zones (SZs) and heat affected zones. As PN increased, these grains were widened due to the increment of the carbon diffusivity and lengthened because of the high heat input and microstructure anisotropy. Besides, increasing the PN causes increasing of the hardness and wear resistance, simultaneously. Specifically, the wear rate in the SZ was reduced from 2.8 × 10⁻² mm³ m⁻¹ in base metal to 0.3 × 10⁻² mm³ m⁻¹ in sample which was subjected to 4 FSP passes. However, variation in PN had no considerable effect on CoFs. Oxidative wear mechanism was observed on the worn surface of the steel and the FSPed samples while more debris was formed by increasing the PNs.
Purpose
This paper aims to present a comparative study of the wear properties of ferrous welded materials like EN8, EN9 and mild steel (MS).
Design/methodology/approach
The material is cut into specific dimension after hardfacing and is studied for the wear properties of the material. The wear testing is done on a pin-on-disc apparatus. The microhardness of the material is studied using the Vickers microhardness measuring apparatus.
Findings
The wear properties of ferrous welded materials like EN8, EN9 and MS are studied. It is found the MS has the least wear when compared to EN8 and EN9. The microhardness of MS is higher than EN8 and EN9, thus making it more wear-resistant than EN8 and EN9. The coefficient of friction in the dry sliding condition is found to be constant throughout the experiment.
Research limitations/implications
Major restriction is the amount of time required for use-wear analysis and replication experiments that are necessary to produce reliable results. These limitations mean that the analysis of total assemblages with the intention of producing specific results, especially of worked materials, is not feasible.
Practical implications
Generally, the complexity and rigour of the analysis depend primarily on the engineering needs and secondarily on the wear situation. It has been the author’s experience that simple and basic wear analyses, conducted in the proper manner, are often adequate in many engineering situations. Integral and fundamental to the wear analysis approach is the treatment of wear and wear behaviour as a system property. As a consequence, wear analysis is not limited to the evaluation of the effects of materials on wear behaviour. Wear analysis often enables the identification of nonmaterial solutions or nonmaterial elements in a solution to wear problems. For example, changes in or recommendations for contact geometry, roughness, tolerance and so on are often the results of a wear analysis.
Originality/value
The value of the work lies in the utility of the results obtained to researchers and users of the EN8, EN9 and EN24 material for their components.
A review of high temperature tribocorrosion is presented focusing attention on those contributions that illustrate the general principles, modeling, and scientific theories of the processes of high temperature wear. A significant aspect of this article is the inclusion of new information on glaze formation, generated at the sub-microscopic and nano-scale level.
The friction and wear behaviors of a new hot-work die steel, SDCM-SS, were studied at high temperature under dry air conditions. The wear mechanism and microstructural characteristics of the SDCM-SS steel were also investigated. The results showed that the SDCM-SS steel had greater wear resistance compared with H13 steel; this was owed to its high oxidizability and temper stability. These features facilitate the generation, growth, and maintenance of a tribo-oxide layer at high temperature under relatively stable conditions. The high oxidizability and thermal stability of the SDCM-SS steel originate from its particular alloy design. No chromium is added to the steel; this ensures that the material has high oxidizability, and facilitates the generation of tribo-oxides during the sliding process. Molybdenum, tungsten, and vanadium additions promote the high temper resistance and stability of the steel. Many fine Mo2C and VC carbides precipitate during the tempering of SDCM-SS steel. During sliding, these carbides can delay the recovery process and postpone martensitic softening. The high temper stability postpones the transition from mild to severe wear and ensures that conditions of mild oxidative wear are maintained. Mild oxidative wear is the dominant wear mechanism for SDCM-SS steel between 400 and 700 °C.
Hardfacing involves the interaction with substrate steel being coated: dilution. Irrespective of the technique, some dilution always occur. In fact, it is required to ensure the metallurgical bond between the coating and the substrate. Usually dilution causes changes on the chemical composition, microstructure and as consequence on the performance of coating. Although these effects have been study at room temperature, the impact of dilution on the high temperature performance is an open subject. This work assessed the effect of dilution on the high temperatures wear behavior of NiCrSiBC alloy processed by plasma transferred arc (PTA) on stainless steel AISI 304. The impact of dilution on the microstructure of the coatings was evaluated by EDX, XRD, SEM-EDS, optical microscopy and hardness; high temperature wear behavior through ball on disc sliding wear test. The results showed that dilution increases suppressed the formation of Cr5B3 borides formation and as consequence hardness decreased. Wear behavior was determined by combined effect of dilution and test temperature. Dilution alters oxidation resistance and the kind of oxides formed; test temperature the amount of oxidation, and both determine tribolayers formation. With increasing of temperature, the coating with higher dilution exhibited the better performance than coatings with lower dilution due a compacted tribolayer formation which almost covering the wear track. This behavior is related with poor oxidation resistance of coating s with higher dilution and Fe content. It drives to a higher debris generation, which can be translated in higher amount of feedstock to tribolayer formation.
A cast iron/low carbon steel sandwich-structured bimetal fabricated through composite casting, followed by hot rolling and hot compression (40% reduction) in a vacuum, and water quenched using Gleeble 3500 thermomechanical simulator. The microstructure of a predominantly martensitic structure is transferred to a matrix with an amount of austenite. The measured results show that the macro-hardness is significantly lower due to the evolution of matrix. A considerable amount of secondary carbides were precipitated from the matrix. This study also shows that a significant difference in the value of coefficient of friction (COF) at the end when hot rolling (HR) was tested under three sets of sliding wear conditions, while those for hot rolling and heat treatment (HT) tends to be merged. An increased wear resistance of interfacial zone is expectable.
The billets of M3 high speed steel (HSS) with or without niobium addition were prepared via spray forming and forging, and the corresponding microstructures, properties were characterized and analysed. Finer and uniformly-distributed grains without macrosegregation appear in the as-deposited high speed steel that are different to the as-cast high speed steel, and the primary austenite grain size can be decreased with 2% niobium addition. Niobium appears in primary MC-type carbides to form Nb6C5 in MN2 high speed steel, whereas it contributes less to the creation of eutectic M6C-type carbides. With same treatments to forged MN2 high speed steel and M3 high speed steel, it is found that the peak hardness of these two steels are almost the same, but the temper-softening resistance of the former is better. With higher high-temperature hardness of the forged MN2 high speed steel, its temper softening above 600 °C tends to slow down, which is related to the precipitation of the secondary carbides after tempering. A satisfactory solid solubility of Vanadium and Molybdenum can be obtained by Nb substitution, precipitation strengthening induced by larger numbers of nano-scaled MC and M2C secondary carbides accounts for the primary role of determining higher hardness of MN2 high speed steel. The results of the wear tests show that the abrasive and adhesive wear resistance of MN2 high speed steel can be improved by the grain refinement, existence of harder niobium-containing MC carbides, as well as solute strengthening by more solute atoms. The oxidational wear behavior of MN2 high speed steel can be markedly influenced by the presence of the high hardness and stabilization of primary niobium-containing MC-type carbides embedded in the matrix tested at 500 °C or increased loads. The primary MC carbides with much finer sizes and uniform distribution induced by the combined effects of niobium addition and atomization/deposition would be greatly responsible for the good friction performance of the forged MN2 high speed steel.
Elevated-temperature wear tests under atmospheric conditions at 400 °C were performed for a hot working die steel H21 on a pin-on-disk wear tester. The phase and morphology of worn surfaces were examined using XRD and SEM, and the relation of wear resistance to tempered microstructures was studied for H21 steel. XRD patterns exhibit that oxidative wear is a predominated wear mechanism with Fe3O4 and Fe2O3 on worn surfaces. It is found that with increasing normal load, obvious plastic deformation of substrate appears on worn surfaces. Microstructures start to affect apparently wear resistance of the steel with an increase of load. Under loads of 50–100 N, wear losses of steel retain low values and relatively approach for steels with various microstructures. As loads are increased to 150 – 200 N, wear losses of steel start to increase obviously and present apparent difference for steel with various microstructures. Wear resistance is found to increase in the sequence as follows: tempered sorbite, tempered martensite, tempered troostite without secondary hardening and tempered troostite with secondary hardening or upcoming one. Higher strength and microstructural stability are required for steels with excellent wear resistance.
The use of chemical-vapor-deposition (CVD)-coated ceramic particle reinforcements in metal-matrix composites allows the control of reactivity at the particle/matrix interface. Wear-resistant, high-speed, steel-based composites containing uncoatedAl2O3 uncoated TiC, and CVD-coated A12O3 were liquid-phase sintered and characterized using pin-on-disk wear testing. TiC or TiN CVD coating of Al2O3 resulted in a porosity decrease at the particle/matrix interface in addition to better ceramic/metal cohesion due to improved wettability. Lower wear rates were obtained with the composites containing TiC-or TiN-coated Al2O3.
Wear is defined as a set of processes of which adhesion, transfer, abrasion, fatigue and oxidation may be some of the constituent processes; these effect transformations of matter from one state to another. The final transformation in wear is attrition in which free debris particles are formed.Oxidation in the wear of metals is discussed, in particular for circumstances in which an oxide layer thick enough for the oxidation rate to be inversely dependent on oxide thickness is formed i.e. the standard relationship (outside the wear situation) between the oxide thickness and elapsed time is parabolic.It is shown that the basic factors determining the wear process are the mechanical characteristics of the oxide layer and that the oxidation process, while important, is a secondary influence.Theoretical considerations show that the oxidation temperature may be lower than the contact temperature, even for oxidation nominally at the contact regions. Also, an oxidation rate in wear may decrease with increasing oxidation temperature, as is sometimes observed in practice. This may be due to an increase in the thickness to which the oxide layer can grow in wear, when the oxidation temperature increases.
The activation energy for oxidation in wear has been determined from sets of experimental data obtained during the dry and unlubricated wear of eutectoid steel rubbing at moderate to high sliding speeds. This value is not very different from the activation energy for the oxidation of cold-worked iron in the same temperature range. It has been observed that the calculation of activation energy is very sensitive to the assumption made for the pertinent temperature of oxidation. In the present work the appearance of wustite (FeO) has been used as an indicator of this temperature.
This book presents the current understanding of the influences of microstructural parameters on wear. The effects of microstructure become more pronounced as the surface contact of two solid bodies becomes closer and these effects can be substantially reduced by oxide layers and lubricant films. The chapters include a general review of microstructure and properties of materials; classification of wear processes, wear mechanisms for grooving wear, sliding wear in metals, polymers, ceramics and composites; and rolling sliding wear and erosive wear of metals. (H.C.B.)
A straightforward treatment describing the oxidation processes of metals and alloys at elevated temperatures. This 2006 second edition retains the fundamental theory but incorporates advances made in understanding degradation phenomena. The first half provides an authoritative introduction to the basic principles, covering thermodynamics and mechanisms of high temperature corrosion of metals and alloys. The latter half extends the discussion to oxidation processes in complex systems, from reactions in mixed environments to protective techniques, including coatings and atmosphere control. The authors provide a logical and expert treatment of the subject, producing a revised edition that will be a comprehensive guide to material scientists and engineers requiring an understanding of this elementary process.
A study of the wear behaviour and microstructure of three high speed steels of the molybdenum type, M1, M15 and M42, has been made in the region of the secondary hardening peak arising during tempering. The maximum wear resistance was found to be associated with the peak hardness. The wear resistance of samples which had been overtempered at tempera- tures beyond the peak hardness was found to be lower than that of samples tempered at temperatures below the peak hardness for samples having the same hardness. In the secondary hardening region in high speed steels many microstructural changes take place since new phases precipitate. These phases are different in size, morphology, composition and crystal structure compared with the previous precipitates. These changes in microstructure cause a deviation from the linear relationship between wear resistance and hardness. In over-tempered high speed steels primary carbides have been shown to act as abrasives which contribute to the drastic fall in wear resistance when steels are tempered beyond peak hardness. Quantitative studies of the type, volume fraction, size and size distribution of primary carbides and measurements of wear resistance have shown that primary carbides have no role in enhancing the wear resistance of high speed steels. Further, the wear resistance of high speed steels is independent of the volume fraction of primary carbides.
Tribological properties are considered as system properties and not as intrinsic properties of materials. The great number of parameters which can influence the wear resistance does not permit one to simply characterize a material as good'' or bad'' for low-wear applications. However, the wear behavior of materials is strongly dependent on microstructural parameters: type and mechanical properties of the matrix, second phase distribution, presence of hard particles, solid lubricants or pores. High speed steels are conventional cutting tool materials with a high wear resistance. The purpose of the present work is the investigation of the microstructure of a powder metallurgical M3 class 2 high speed steel before and after tempering at 600[degree]C, by means of the development of Quantitative Image Analysis (QIA) techniques for analyzing complex microstructures such as those exhibited by high speed steels. In particular, the effect of tempering on the mean size and distribution of the primary M[sub 6]C and MC carbides, as well as on the porosity, is studied. These microstructural features influence to a significant degree the general wear behavior of high speed steels. Therefore, the results of Quantitative Image Analysis are discussed in association with the role of primary carbides and porosity on the tribological properties of the studied material.
Cu–P alloy powder additions to M3 class 2 high speed steels reduce the sintering temperature required to produce near full density by ∼100 K. Densification was found to occur in distinct stages, due to the successive formation of a series of liquid phases at various sintering temperatures. These phases, each of which gave rise to an identifiable change in densification rate, were identified as the ferrite-carbide-phosphide eutectic at ∼1050°C, melting of residual copper at 1090°C, and an austenite-carbide eutectic at 1150°C. An activated sintering model for densification by the formation of a phosphide rich grain boundary liquid was developed. This concluded that sintering occurs by rapid grain boundary migration due to solutionprecipitation across an unstable grain boundary liquid film. PM/0512
The potential of Wear-Mechanism Diagrams is explored. Diagrams which show the rate and the regime of dominance of each of a number of mechanisms of dry wear (delamination, mild and severe oxidation, melting, seizure, etc.) are constructed empirically (that is, from experimental data alone) and by modelling (by theoretical analysis calibrated to experiment). The method is applied to steels, and has wider application as a way of classifying and ordering wear data, and of showing the relationships between competing wear mechanisms.RésuméNous explorons les possibilités des diagrammes de mécanismes d'usure. Nous construisons empiriquement (c'est à dire, à partir des seules données expérimentales) et à l'aide de modèles (grâce à des analyses théoriques étalonnées sur l'expérience) des diagrammes qui fournissent la vitesse et le régime de prédominance de chacun des mécanismes d'usure sèche (délamination, oxydation légère et prononcée, fusion etc). Nous appliquons cette méthode aux aciers, mais elle a des applications plus larges en tant que moyen de classification et de tri des données d'usure, ou pour montrer les relations entre les mécanismes d'usure en compétition.ZusammenfassungDie Anwendungsmöglichkeiten von Diagrammen der Abriebmechanismen werden untersucht. Diagramme, die Geschwindigkeit und Bereich des Auftretens einer Reihe von Mechanismen des trockenen Abriebes (Delamiantion, schwache und starke Oxidation, Schmelzen usw) aufzeigen, werden empirisch (d.h. aus experimentellen Werten) und im Modell (d.h. durch theoretische, an das Experiment angeglichene Analyse) konstruiert. Diese Methode wird auf Stähle angewendet. Sie hat einen weiteren Anwendungsbereich, indem sie Abriebdaten klassifizieren und ordnen und die Zusammenhänge zwischen konkurrierenden Abriebmechanism en aufzeigen kann.
The oxidational theory of mild wear is reviewed with special emphasis on attempts to deduce the contact radius a, the number N of contacting asperities, the critical oxide film thickness ξ and the temperature To at which the real areas of contact oxidize through the simultaneous measurement of the wear rate wexpt, the division of heat δexpt at the sliding interface and the general surface temperature Ts. A new expression is derived from the oxidational wear theory and the thermal characteristics of a pin-and-disc sliding wear system in which only one parameter, the contact radius a, is involved. The solution of this new expression by an iterative technique leads to values of a, ξ, N and To consistent with previous (intuitive) estimates of these quantities for the particular instance of EN8 steel sliding against itself at 2 m s⁻¹ under a series of loads from about 4 to 40 N. The iterative technique is also applied to pin-and-disc experiments with EN31 steel sliding against itself at 4 and 5m s⁻¹ under loads varying from 4 to 55 N.
The origins and the development of the oxidational theory of mild wear under conditions where the ambient temperatures are sufficiently low that no significant oxidation can occur outside the instantaneous real areas of contact between two sliding surfaces are reviewed in this paper. Emphasis is placed on the importance of heat flow analysis for calculating surface temperatures and the division of heat at the sliding interface, especially in so far as it is used for checking the surface model used for explaining the wear rates obtained in some pin-on-disc experiments with low alloy steels. It is shown that it is possible to deduce values for the oxidation constants during wear that are different from those obtained from static oxidation tests and which are relevant to a range of low alloy steels. The implications of some of the computed values of the number N of asperities beneath the pin at any given time, the temperature Tc within the real areas of contact and the critical oxide film thickness ξ are discussed.
This paper reviews the more recent work carried out on one of the three main mechanisms by which wear can occur between metal surfaces in relative motion, namely by oxidational (or mild) wear. It deals with the temperatures produced at sliding interfaces and with the influence of a simple surface model upon the thermal and wear aspects of surface interactions. The fundamental aspects of the oxidational wear theory are reviewed, as well as some recent experiments (involving the mild wear of steels) which have been undertaken to test the validity of this theory.
Wear behaviour of 52100 low alloy steel has been studied on a pin on disc wear machine at disc temperatures ranging from room temperature to 500°C. Transitions occur in the wear rate versus load curves at certain critical loads, the magnitude of which increase with temperature. These transitions were found to be associated with change in surface oxide, lower wear rates being recorded when the predominant oxide was the spinel Fe3O4 for all temperatures. At disc temperatures above 300°C out of contact oxidation appears to be the most important wear limiting factor. A surface model was developed enabling contact temperature, numbers and size of contacts and critical oxide film thickness to be deduced. Remarkable agreement was found between oxide thicknesses estimated from this model and measured values using a scanning electron microscope
The wear behaviour of sintered high-speed steel-type particulate composites depends significantly on microstructural parameters, such as those of the metallic matrix and primary carbides, but also on some additional parameters related to the powder metallurgy processing. Pin-on-disc test results, coupled with scanning electron microscopy (SEM) observation of the wear tracks and microstructure image analysis, indicated the prominent role of the added ceramic particles. More precisely, the size, the mechanical resistance and the cohesion with the metallic matrix of TiC, uncoated Al2O3, and TiN-coated Al2O3 particles, largely determine the wear behaviour of such materials. In addition, the roles of the residual porosity and of the presence of copper as a solid lubricant are pronounced in this investigation.
A new theory for wear of metals is considered. The theory is based on the behavior of dislocations at the surface, sub-surface crack and void formation, and subsequent joining of cracks by shear deformation of the surface. The proposed theory predicts qualitatively that the wear particle shape is likely to be thin flake-like sheets and that the surface layer can undergo large plastic deformation. It also predicts a number of experimentally observed phenomena such as the difference in wear particle sizes and the dependence of fretting wear rate on displacement amplitude. All theoretical predictions are supported by experimental evidences. A wear equation is developed based on the proposed theory.
TIZZY -Friction, Lubrication and Wear, Fi$y Years On
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Vardavoulias and M. Jeandin, presented at the 7th Int. Conf. Surface Modification Technologies
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