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The effects of substrate dilution on the microstructure and wear resistance of PTA Cu-Al-Fe aluminium bronze coatings
Abstract
Cu-Al-Fe aluminium bronze alloys are good candidates for precious tools and forming dies due to their high wear resistance, good sliding properties and low tendency for adhesion to ferrous metals. Plasma transferred arc (PTA) is an effective process for deposition of such robust coatings by enhancing the bond between the bronze coating and steel substrate. However, the microstructure and wear characteristics of these coatings are strongly influenced by the diffusion of substrate elements (mostly iron) to the interface. In the present study, the effects of substrate dilution on the microstructure and wear behaviour of Cu-Al-Fe alloy deposited by PTA on medium carbon steel substrate were investigated. The results show that the deposition current controls the melting temperature and iron dilution which result in the formation of Cu3Al martensitic β1' phase in a low dilution and the ordered β1 phase in high dilution. The wear behaviour of the coating is dominated by failure of the matrix phase. Low dilution coating with martensitic phase exhibits the highest wear resistance. On high diluted Fe rich coating, pile up of dislocation on the intermetallic K phase leads to surface cracks and delamination of the coating resulting in a high wear rate.
... The steel/bronze composite materials can be fabricated using different methods including smelting-casting, brazing, welding, jet binding or plasma-transferred arc deposition [2][3][4][5][6] that would allow obtaining products with properties combining good processability with high corrosion resistance or strength and toughness with high heat-and electric conductivities. ...
... Plasma-transferred arc (PTA) process was used for deposition of a Cu-Al-Fe coating on the EN10503 steel substrate and studying the effect of dilution on the resulting coating's microstructure [2]. The amount of κ-phase precipitates was depending on the amount of Fe admixed to the bronze. ...
... It is worthwhile to note that the transition zone is free from defects such as pores, cracks or discontinuities despite their presence being reported elsewhere [2,15]. The reason behind such a finding is using the higher heat input when depositing the first several layers. ...
Electron beam additive manufacturing with simultaneously controlled feeding and melting of ER321 stainless steel and CuA19Mn2 bronze wires was carried out. The composite microstructure was formed consisting of homogeneously distributed ferrite and nickel-enriched bronze grains. Intensive intermixing and diffusion in the melted pool caused redistribution of nickel from stainless steel to the bronze and solidification of ferrite grains instead of the austenitic ones. Dispersion hardening of both ferrite and aluminum bronze grains occurred by core/shell β′/AlNi and AlFe3 (κiv-phase) precipitates, respectively, that resulted in improving the ultimate tensile stress and increasing the microhardness of the composites depending upon the content of stainless steel introduced. Deformation was localized mainly in the bronze grains while ferrite grains retained their shape and were almost free of dislocations. The bronze grains allowed revealing only small regions containing the deformation microtwins. The tensile strength and microhardness of the composite samples were increased as compared to those of the pure bronze. No anisotropy was found during tensile testing.
... However, all AS samples had a stable friction behavior with a short run-on stage and uniform CoF after process stabilization. The value of wear was also different for different printing conditions; however, in general, it was typical for aluminum bronze [30,31]. SEM analysis of friction surfaces (Figure 8b) showed a similar wear mechanism for all structure states. ...
... That is why annealed martensitic samples possessing hardness lower than β1 samples exhibited less wear. Intermetallic inclusions of solid phases also helped to significantly improve the characteristics of Cu-Al bronzes under dry friction [31]. ...
In this work, the method of electron beam additive manufacturing (EBAM) was used to fabricate a Cu-based alloy possessing a shape memory effect. Electron beam additive technology is especially relevant for copper and its alloys since the process is carried out in a vacuum, which makes it possible to circumvent oxidation. The main purpose of the study was to establish the influence of the printing parameters on the structure of the obtained products, their phase composition, mechanical properties, dry friction behavior, and the structure-phase gradient that formed in Cu–Al–Mn alloy samples during electron beam layer-by-layer printing. The results of the study allowed us to reveal that the structure-phase composition, the mechanical properties, and the tribological performance of the fabricated material are mainly affected by the magnitude of heat input during electron beam additive printing of Cu–Al–Mn alloy. High heat input values led to the formation of the β1′ + α decomposed structure. Low heat input values enabled the suppression of decomposition and the formation of an ordered 1 structure. The microhardness values were distributed on a gradient from 2.0 to 2.75 GPa. Fabricated samples demonstrated different behaviors in friction and wear depending on their composition and structure, with the value of the friction coefficient lying in the range between 0.1 and 0.175.
... In recent years, the use of highly concentrated sources for surface alloying of structural steels has been increasingly carried out with numerous successful results, including electric arc plasma heating, which provides sufficient heat with high efficiency, short processing time [19,20,21]. To improve the properties of surface hardening, a number of works have already reported on plasma heating of aluminum bronze [22], a mixture of tin bronze and an iron alloy [23], laser cladding of immiscible nanocomposites of the Cu-Fe-Cr-Si-C systems [24], Cu-Fe -Ni-Cr-Si [25], Cu-Ni-Fe-Mo-xCr [26]. However, the number of studies on obtaining an alloyed layer of the Fe-Cu-Sn system is still small, and the quality of the resulting coatings does not meet the expected requirements associated with high hardness, wear resistance, etc. Abrasive wear is one of the most common types of wear. ...
... In practice, abrasive and other wear mainly cause mechanical damage to metal parts of machines, especially moving parts. Studies on wear resistance have been repeatedly carried out, but mainly only for coatings and alloys of the systems Fe-Cu-Sn [15], Fe-Cu [22], Cu-Sn [27], Cu-Sn-Cr [28]. For alloying the surface of carbon steel, it was proposed to use coatings of the Fe-Cr-C-Cu-Sn system [20]. ...
This paper presents a study of the characteristics and resistance to abrasive wear of surface alloyed layers during plasma heating of powder pre-coating of a mixture containing tin bronze and chromium carbide. It has been established that, depending on the composition of the mixture, the thickness of the coating, the processing mode, the resulting layers differ in structure, chemical and phase composition. The addition of chromium carbide with a mass fraction of 20% makes it possible to increase the microhardness of the alloyed layer based on tin bronze up to 700 HV with the formation of a martensitic structure. Tests for abrasive wear were carried out at a load of 5, 20, 50 N and with codirectional rotation of the holder to the abrasive wheel. The obtained results showed that the wear resistance of the Fe-Cu-Sn and Fe-Cr-C-Cu-Sn alloyed layers is higher compared to the Cu-Sn layer. In particular, the Fe-Cr-C-Cu-Sn layer is the best.
... This alloy is compared to high strength and low alloy steels due to its mechanical strength, and also due its high corrosion resistance, similar to stainless steels. Thus, it is used in the marine and aerospace industries in components such as bushings and landing gear bearings, propellers and ship rotors, hydraulic pumps, and pipelines for the oil and gas industry [1][2][3][4]. ...
... Complex alloys, such as aluminum bronze, to which have been added alloying elements, such as Fe and Ni, present beyond the α and β phases, the intermetallic κ compounds and their variations in addition to the martensitic β' phase when subjected to some heat treatment to increase their mechanical resistance. The κ phase is divided into iron-rich κ phases based on Fe 3 Al compounds, and nickel-rich κ phases based on NiAl [2,5,6]. ...
This article analyzes the influence of mechanical ball milling parameters on processed aluminum bronze chips in order to increase the efficiency of this process in terms of particles' size reduction. Also evaluated is the addition of vanadium carbide (VC) in this response, along with its microstructure and magnetic properties. The experiments have been carried out in accordance with DOE design methodology. After machined, its residues can still be reused to produce composites through powder metallurgy routes, preserving good mechanical properties without onus to the environment. The study aims to produce and characterize powders resulting from ball milling processes, identifying the influential parameters, in addition to verify its soft magnetization behavior. The powder morphologies and particle sizes underwent scanning electron microscopy (SEM), coupled with energy-dispersive spectroscopy (EDS) and laser diffraction particle analyses, respectively, in addition to phase identification via X-ray diffraction (XRD). Moreover, saturation magnetization (Ms), remanent magnetization (Mr), coercivity (Hc), and remanence-to-saturation ratio (Mr/Ms) were determined through magnetic hysteresis curves obtained from a vibrating sample magnetometer (VSM). Results indicate that % VC and milling time are the main parameters to improve the milling efficiency and obtain submicrometric particles with sizes almost 800 times smaller than the initial chips. After the milling process, aluminum bronze powders presented certain amorphization, a decrease of about 24% in Ms and an elevation about 81% in Hc, both compared with the as cast material. The Mr/Ms ratio indicates a slight conservation of magnetization.
... Under such circumstances, flux-cored wires constitute the best choice owing to the ease of regulating the chemical composition. In addition, the welding wire is always accompanied by penetration of matrix elements during the cladding process [24][25][26], which leads to dilution of the Cr element in the cladding layer. An increase in the Cr content of flux-cored wires would be able to compensate for Cr dilution during cladding, which in turn would decrease the Cr-depleted area in the cladding layer. ...
Arc welded 316 stainless steel coatings with flux-cored wires are very promising for marine service environments due to their low cost, high efficiency, and satisfactory performance, while they suffers from Cr dilution during the preparation process. Herein, based on the consideration of increasing the Cr content and ensuring the same value of the Cr/Ni equivalence ratio (Creq/Nieq), 316-modified flux-cored wires, 316F (19Cr-12Ni-3Mo) and 316G (22Cr-14Ni-3Mo), were designed under the guidance of a Schaeffler diagram for the improvement of the electrochemical and mechanical properties of 316 stainless steel coatings. The designed flux-cored wires were welded into a three-layer cladding by the tungsten inert gas welding (TIG) process, and the microstructure, corrosion resistance, and mechanical properties of the claddings were investigated. The results showed that 316F and 316G consist of γ-Fe (austenite) and a small portion of δ-Fe (ferrite) as the Creq/Nieq is approximately 1.5. However, due to the higher value of the equivalent Cr content (ECC), 316G has an additional intermetallic phase (σ), which precipitates as a strengthening phase at grain boundaries, significantly increasing the tensile and yield strength of 316G but reducing its plasticity. In addition, the corrosion current density (icorr) and pitting potential (Eb) for 316G are 0.20447 μA·cm⁻² and 0.634 V, respectively, while the values for 316F are 0.32117 μA·cm⁻² and 0.603 V, respectively, indicating that 316G has better anti-corrosion performance.
... The worn surface analysis showed transition from oxidative wear to adhesive wear as the test temperature was increased. Kucita et al [12] studied the wear resistance of Cu-Al-Fe aluminium bronze castings when subjected to dry sliding wear. The wear test showed decrease in friction coefficient with the increase in the applied load. ...
Copper alloys with the main alloying elements Zn, Al, and Ni are well known for their impact, wear, and corrosion resistance. Different fabrication techniques and alloying elements can be used to modify the microstructure and properties. The effect of shell mould and permanent mould techniques on the microstructure, microhardness, and wear behaviour of high tensile brass and nickel aluminium bronze (RB031, RB032, and NAB) was investigated in this work. For permanent mould fabricated alloys, optical microscopic analysis revealed a homogeneous microstructure with fine grains. The RB032 alloy had a higher proportion of Mn5Si3 particles than the other two high tensile brasses (RB031 and RB032). In the case of NAB alloy, both fabrication techniques revealed similar phases composed of - phase,'phase, and intermetallic phases (I, II, III, and IV). Higher cooling rates in Permanent Moulded Cast alloys resulted in equiaxed structures, which were especially noticeable in RB032, which had 31% smaller grain size than Shell Moulded Cast alloy. RB032 (PM) microhardness values were 2.3% higher than Shell Moulded (SM), with RB032 exhibiting the highest increment. Permanent Moulded alloys outperformed Shell Moulded alloys in terms of friction and wear rate, with RB032 (PM) having 44% lower friction and 5.8% lower wear rate. The wear mechanisms differed, with RB031 exhibiting abrasive wear and RB032 and NAB(AB2) exhibiting adhesive wear.
... It was shown that the material strength, hardness, and friction coefficient values decreased due to the forging process. Kucita et al. [16] investigated the effects of coating Cu-Al-Fe aluminum bronze alloys with plasma transferred arc method on wear behavior and microstructure. As a result of the study, reductions in the coefficient of friction were determined under dry friction conditions with the coating. ...
Aluminum bronze alloys produced by various methods are preferred materials in many fields of the industry due to their high wear resistance and good sliding properties. This study investigated the tribological properties of aluminum bronze alloys produced by forging from Cu, Al, Fe, and Mg elements. Dry sliding wear tests were carried out on a pin-on-disc wear device. Three tribological properties, wear, friction coefficient, and temperature of aluminum bronze alloys were investigated. Experimental studies were carried out for different loads, sliding speeds, and sliding ways. The factorial experiment design method was applied in the MINITprogram. A SEM visualized the samples microstructures to examine the material wear characteristics. As a result of the study, it was deter-mined that the applied load, sliding speed, and sliding way were effective parameters on the amount of wear and friction coefficient. The maximum amount of wear was 0.352 mg at 100 N load, 3 m/s sliding speed, and 3000 m sliding way conditions. The maximum temperature between materials under these conditions is 299 oC. The minimum amount of wear was obtained when 25 N load, 1 m/s sliding speed, and 1000 m sliding way were applied.
... Surfaces modification of tool materials to enhance their mechanical properties and be more wear-resistant by exploiting surface treatments (nitriding, laser surface alloying, texturing, etc.) [12,18,33,34], deposition of thin layers (PVD, CVD) [35], or development of thick coatings (PTA, plasma spray, etc.) [36][37][38] has shown promising growth. Nonetheless, the widely used technique of thin coatings (<1-3 μm) is often unsuited in applications of high load and harsh temperatures (current work) owing to their material and structural limitations instigated by their small-scale thickness [36,39,40]. In this regard, thick coatings such as those developed by laser cladding offer a prospect. ...
To increase the performance of the tool materials operating at high temperatures (HT), the protection of the surface from wear is usually needed. Conventional lubricants pose problems due to their degradation and harmful effects on human health; therefore, self-lubricating materials are of great importance. In the current work, self-lubricating NiCrSiB millimeter-thick composite coatings with the addition of solid lubricants Ag and MoS2 were fabricated on stainless steel substrates using laser metal deposition. Upon microstructural analysis, it was revealed that the addition of MoS2 resulted in a uniform distribution of Ag throughout the coating thickness owing to a unique phenomenon of silver encapsulation. Further, the coatings were subjected to sliding wear tests against an alumina counterbody at a load of 5 N, a speed of 0.1 ms−1 , and a distance of 500 m under a unidirectional condition in a ball-on-plate configuration. The tests were performed from 20 to 800°C. The results show that self-lubricating composite coatings demonstrate an exceptional performance up to 800°C. Significant friction (best at 800°C ⁓0.25) and wear (best at 600°C ⁓4.3 times less) reduction for Ag + MoS2 added coating is seen. It was revealed that the presence of CrxSy and Ag on the wear track delivered lubrication at temperatures ≤400°C while, a glazed tribolayer rich in silver molybdate phase (along with CrxSy , MoO3) was an effective lubricant at 600 and 800°C. The results are reported in comparison to the unmodified Ni-based alloy.
... Leonardo et al. [30]. and Kucita et al. [31] have reported that dilution in the metallic coatings not only impacts the chemical composition but also strongly influence the microstructure and mechanical properties. ...
This work investigates the impact of high-temperature corrosion behavior of the newly developed FeCrAl alloy Kanthal ® EF101 bulk material and weld overlay coating in the presence of KCl(g)/KCl(s) at 600 C. The oxide scale formed within the secondary corrosion regime after exposure and the impact of alloy microstructure on corrosion behavior was investigated using scanning transmission electron microscopy. The findings indicated the key microstructural differences is the alloy grain size which influences the formation of a protective scale. In addition, It is indicated that coating exhibited inferior performance than the bulk material, primarily attributed to the microstructural differences.
... These authors established that this treatment increases the micro-hardness and decreases the tensile residual stresses in the near-surface layer of nickel-aluminum bronze. Kucita et al. [22] investigated the wear resistance of Cu-Al-Fe aluminum bronze coating deposited via plasma transferred arc on medium carbon steel substrate. A low-dilution coating with a martensitic phase exhibited the highest wear resistance. ...
The effect of diamond burnishing (DB) on the wear resistance of two-phase CuAl9Fe4 bronze sliding bearing bushings was investigated experimentally via assessments of the surface integrity (SI) following different finishing processes, sliding wear tests and worn surface morphology analyses. The wear tests were performed under boundary lubrication and dry friction conditions. One- and six-pass DB increase wear resistance under boundary lubrication by 1.69 and 2.55 times, respectively, compared to the fine turning process. Under the dry friction condition, these increases amount to 2.27 and 2.15 times, respectively. Under boundary lubrication, the dominant wear mechanism is the micro-cutting inherent in abrasion; therefore, the geometric characteristics of surface integrity (SI) play a decisive role in mass wear. DB leads to a favourable combination of the 3D height and shape parameters for surface texture (ST), which improves lubrication and hence reduces friction and mass wear. Under dry friction, the dominant wear mechanism is adhesion for fine-turned specimens and abrasion for diamond burnished specimens. The physical-mechanical condition of the surface layer is dominant in terms of wear, and ST is of secondary importance for this friction regime. DB leads to significant improvements in the SI physical-mechanical characteristics.
... In addition, PTA method has attracted the attention of researchers in recent years due to its high welding speed, well penetration depth and good arc stability, as well as its wear-corrosion resistance and improved fatigue strength [8][9][10][11]. In particular, in this method, besides the wide range of materials, the performance of the material surfaces can be greatly improved by low dilution and deterioration between the hard filler layer formed on the coated surfaces and the substrate material [12][13][14][15][16]. Plasma transferred arc (PTA) technique provides strong metallurgical bond formed between the coating and substrate, low porosity, high energy conversion efficiency, high precipitation rate, low heat input [17]. ...
To meet the requirements for materials used in the Advanced Ultra-Supercritical (A-USC) steam condition at an inlet temperature up to 760 °C which enables to increase the efficiency of coal-fired power generation and reduce its CO2 emission, a newly developed Tribaloy alloy T-400C is deposited on a Ni-based alloy Haynes 282 via plasma transferred arc (PTA) welding. The PTA hardfacing specimens are subjected to different post-welding heat treatments: solution annealing at 1135 °C for 1 h plus double aging at 1010 °C for 2 h and at 788 °C for 8 h, and double aging only. They then experience long-time thermal exposure at 760 °C, 815 °C and 871 °C for different times up to 30,000 h. Microstructures of hardfacing, fusion zone and substrate of the PTA specimens before and after long-time aging are studied using SEM/EDS/XRD. It is shown that PTA welding results in a hypoeutectic microstructure of the T-400C hardfacing, with new phases generated. Long-time aging can alter the microstructural morphology with increased amount and coarsening of the Laves phase, Ti-rich and Al-rich phases in the hardfacing. On the other hand, the post-welding heat treatments restore Haynes 282 substrate to its fully aged state containing precipitates, carbides and intermetallics. The microstructure of the fully aged substrate remains stable at temperature of 760 °C, but the phase particles apparently become coarsened as the exposure temperature is increased. The γ' precipitates growth kinetics and coarsening rates are investigated in terms of the LSW theory, and the results show good agreement with the experimental observations.
Controlling heat transfer in casting tools is a key quality aspect. It can be improved by selectively applying volumetric aluminum bronze (CuAl9.5Fe1.2) sections in the core of the tools and subsequently depositing these cores with hard-facing H13 tool steel. Directed energy deposition (DED) can be used for both additive manufacturing of aluminum bronze and hard-facing by depositing the filler material onto a substrate surface or previously manufactured bodies. A sufficient metallurgical bonding of the deposited filler material and the underlying layer must be ensured. Hence, the dilution is a key factor for quality assurance. However, high dilution of the underlying layer and the filler material negatively affects the desired properties and must be monitored. Optical emission spectroscopy of the DED process emissions is investigated by comparing the emission lines of the individual elements comprising the base and the filler materials. Multiple single tracks using aluminum bronze as the filler material are laser-cladded with varying power, onto the two different types of substrates, i.e., mild steel S355 (1.0570) and hot working tool steel H11 (1.2343). Additionally, single tracks of H13 (1.2344) are deposited with varying laser powers onto an additively manufactured core of aluminum bronze. Both resulting in deposition tracks with varying dilution values. Multiple emission lines of Cr, Fe, Cu, Al, and Mn are detected and measured (line intensity). Line intensity ratios using the element emission lines are calculated and correlated with the respective metallographic results of the deposition tracks (dilution and chemical composition). Deposition tracks with a higher dilution (CuAl9.5Fe1.2 onto S355/H11 as well as H13 onto CuAl9.5Fe1.2) showed an increased line intensity ratio of the underlying material to the filler material. Moreover, this technology was transferred in a multilayer industrial application.
In this study, the effects of milling time and heat treatment on microstructure and wear behavior of Cu-Al-Ni shape memory alloys produced by the mechanical alloying method were investigated. Cu-Al-Ni shape memory alloys were produced by mechanical alloying in four different durations (2.5, 5, 7.5 and 10 h) in a planetary-type mill. The produced Cu-Al-Ni shape memory alloys were characterized by microstructure (SEM + EDS), x-ray diffraction, thermal analysis (TG/DTA-DSC), and hardness, density, and dust size measurements. In the wear tests, three different loads (10, 20, and 30 N), five different sliding distances (400, 800, 1200, 1600, and 2000 m) and a sliding speed of 1 ms−1 were used. As a result of the studies, it was observed that the powder size decreased with the increase in MA time. It was observed that the density of heat-treated shape memory alloys decreased compared only to sintered alloys. According to the wear test, the lowest wear rate was obtained in Cu-Al-Ni shape memory alloys exposed to mechanical alloying for 7.5 h, with the highest hardness value. In addition, it was observed that the wear rates decreased in heat-treated Cu-Al-Ni shape memory alloys as the sliding distance increased.
The authors investigated the microstructure, phase composition and mechanical properties of the steel-bronze composite obtained by electron
beam additive manufacturing with simultaneous supply of aluminum bronze wires BrAMc9-2 and stainless steel 06Kh18N9T. X-ray diffraction
analysis revealed that the composite contains 25 % (vol.) of aluminum bronze, which leads to the formation of a three-phase structure consisting
of γ-Fe, α-Fe and α-Cu grains. According to scanning electron microscopy, the volume fraction of austenite, ferrite and bronze in the steel – 25 %
bronze composite is 40.7, 35.7 and 23.6 %, respectively. Unstable conditions of the electron beam additive manufacturing process lead to the release
of dispersed particles in austenite and ferrite grains. Dispersion-hardened copper particles with an average particle size of 40 nm, the volume fraction
of which is 47 %, are isolated in austenite grains. Dispersion-hardened NiAl particles with a volume fraction of 20 % are isolated in ferrite grains,
the average size of which is 44 nm. Transmission electron microscopy data indicate the coherent conjugation of arrays of dispersion-hardened particles
with the matrix. Such a composite structure provides an increase in yield strength and tensile strength by an average of 400 and 600 MPa compared
with yield strength and tensile strength of 06Kh18N9T steel obtained by electron beam additive manufacturing without bronze addition. Microhardness
of the composite is on average 2.2 GPa, which is 0.4 GPa higher than that of 06Kh18N9T steel obtained by electron beam additive manufacturing
without bronze addition.
To address the challenges of liquid metal embrittlement (LME) cracks and low bonding strength at the Sn bronze/steel liquid–solid compound interface, an innovative Sn bronze/Al bronze/steel laminated composite is fabricated using a wire arc additive manufacturing (WAAM) process, which involved introducing an Al bronze interlayer. The microstructure of interlayer and its related interfaces, as well as the mechanical properties of the composites, are investigated. Results show that the microstructure of Al bronze is mainly composed of α‐Cu and β‐Cu3Al. An interdiffused layer with a maximum thickness of 5 μm exists at the Al bronze/steel interface, which plays an important role in interface adaptation. The Sn bronze/Al bronze interface possesses a 30 μm α(Cu–Al–Fe) transition layer, and the continuous transition of α + β → α(Cu–Al–Fe) → α(Cu–Sn) from the base material to the clad layer is realized. No LME cracks are found in the steel after the Al bronze and Sn bronze deposition. The Al bronze/steel and Sn bronze/Al bronze interfaces exhibit strong bonding strengths of 395 and 361 MPa, respectively.
In this study, three composite coatings were prepared by laser cladding, selecting the ceramic particles (B4C, TiC, or NbC), together with the powders of high-entropy alloy (HEA), i.e. CrMnFeCoNi. The results demonstrate that the composite coatings reinforced by varied carbides exhibited special microstructures, which lead to the features of micro-cutting wear, three-body wear, and fatigue wear, respectively. Therefore, the differences between the three composite coatings were compared, and evaluated in terms of phase structure, microstructure, chemical composition, nanoindentation, and phase interface correlation. Ultimately, the wear resistance mechanisms of selected ceramic particles reinforced HEA coatings were explained, and their applicability was estimated.
Continuous casting spur gear with uniform microstructure and excellent performance remains challenging due to the intensive radial heat flux and nonuniform circumferential cooling in the traditional cooling mold. In this paper, a novel process for manufacturing spur gear with uniform microstructure and excellent strength-ductility synergy by warm mold continuous casting was proposed. The effects of the warm mold continuous casting process on the microstructure and mechanical properties of the QAl9-4 aluminum bronze spur gear billets were systematically studied by simulations and experiments to evaluate the effectiveness of the process. The induction heated mold reduces the radial temperature gradient while improving the vertical temperature gradient. The cooling rate was uniform at the transvers section of the spur gear and increased with increasing casting speed and mold temperature. Spur gear billets with good surface quality, dimensional precision and uniform microstructures were successfully prepared by warm mold continuous casting, and had excellent tensile stress and elongation of 692 MPa and 41%. The synchronously improved strength and ductility of the continuously cast QAl9-4 aluminum bronze spur gear billets results from a higher volume fraction of micron-sized fine α grains and numerous submicron-sized as well as nanosized coherent Fe-rich κ precipitates. The present process could be beneficial for manufacturing high-quality spur gear more efficiently and may also introduce a promising method in integrated control of shape, microstructure and performance of metallic products by continuous casting.
In this paper, the effects of heat treatment on microstructure and properties of modified aluminum bronze alloy coatings were studied. In order to clear out this question, Cu-7Al-3Fe-3Ni alloy was fabricated on 316 stainless steel by laser cladding. And a subsequent heat treatment which tempered four samples at 500, 600, 700 and 800 °C for 1 h, respectively. The deposited coatings mainly contained α-Cu, β’(AlCu3), κ((Fe,Ni)Al) and Cr-Fe phases according to the analysis of XRD and SEM images. After tempered at 500 °C for 1 h, content of κ phase in the coating increased, and there was residual β’ phase. These two hard phases made the coating tempered at 500 °C had the lowest coefficient of friction and wear rate. Then with the increase of tempering temperature, both α-Cu and other phases became coarsen. The results of microhardness showed that the microhardness was significantly improved after heat treatment. Especially, the samples which tempered at 500 °C for 1h showed a better performance of microhardness. With the tempered temperatures increased, the microhardness at interface decreased from 517 HV (500 °C) to 312 HV (800 °C). The EBSD results showed that there was no obvious preferred orientation for grains of deposited and tempered samples, and the Schmidt factor and KAM were both significantly decreased after heat treatment.
The control of Fe dilution and carbide dissolution plays a vital role on the performance of metal matrix composite hardfacings. In this paper, the NiCrBSi–WC composite hardfacing is deposited on 304 austenitic stainless steel by plasma transferred arc hardfacing at 120[Formula: see text]A (specimen 1) and 140[Formula: see text]A (specimen 2) transferred arc current values to obtain different levels of Fe dilution and W dissolution for comparative investigations. The Fe dilution examined by scanning electron microscopy for specimen 1 was 24.54% and for specimen 2 was 33.09%. The microstructural investigations revealed higher W dissolution for specimen 2 due to higher heat input which led to significant reduction in the amount of WC and W 2 C hard phases. The slurry abrasive wear test performed as per ASTM G105 showed two times reduction in abrasive wear resistance of specimen 2 as compared to specimen 1. The significant reduction in the performance of specimen 2 is mainly due to higher Fe dilution and higher W dissolution caused due to higher heat input. Hence, selection of appropriate process parameters is vital to control Fe dilution and carbide dissolution in order to achieve superior performance of composite hardfacings.
Electrolytic plasma hardening (EPH) provides more rapid hardening than conventional hardening processes, including minimum distortion in the parts. The influence of overlapping ratio (Overlapped 10%, 50%) in EPH was compared on hardness, microstructure geometry of the hardened zone and overlapping zone. Reciprocating sliding wear tests were carried out on modified and overlapped AISI 1040 steel. The surface morphology and wear surface were analyzed by scanning electron microscope. The microhardness of modified layer was investigated. The results show that the hardness of AISI 1040 steel is approximately 250 HV0.2, and the hardness after EPH surface heat treatment is around max. 1000 –1050 HV0.2. The single-track EPH modified samples show the best wear resistance. The overlapped zone is the tempered zone and consist of sorbite and tempered martensite. The hardness of sorbite is significantly lower than that of martensite. Therefore, the AISI 1040–10% and AISI1040-50% samples’ wear resistance decrease with overlapping
Alloy steel 17Cr2NiSiMo coatings with small amounts (<1 wt%) of added Y2O3 nanoparticles are fabricated by plasma-transferred arc. The combined effect of the Y2O3 nanoparticles and Si-oxide second-phase particles on microstructure, sliding wear resistance, and wear weight loss of the alloy steel coating are investigated. The Y content in the spherical Si-oxide particles is found to increase with the addition of Y2O3 nanoparticles, as Si provides second-phase oxide particles for Y to accumulate in the coating material during the rapid cooling solidification. Thus, the Fe-based coating is refined and purified, resulting in a low defect or slag concentration. The wear mechanism of the modified coating transforms from third-body interaction and plastic deformation to slight peeling, as dendritic grains in the coating are transformed into equiaxed grains. The wear performance of the modified coating is obviously enhanced with the addition of 0.4 wt% Y2O3 nanoparticles, as indicated by the reduction of its wear weight loss to 20.55% and increase of its relative wear resistance to 25.87%.
This paper reports on investigations of wear characteristics of the Stellite 6 coating on AISI 4130 steel substrate using micro-plasma transferred arc (µ-PTA) powder deposition process. Effects of plasma power, powder mass flow rate and travel speed of worktable have been studied in terms of secondary dendritic arm spacing, microstructure, dilution, line scan analysis and microhardness for enhancement of wear resistance of the Stellite coating. Travel speed of worktable was found to be the most important parameter affecting wear characteristics of Stellite coating. Its higher value gives smaller secondary dendritic arm spacing (SDAS) value and minimum dilution with almost no transfer of iron to Stellite coating. Analysis of microstructure, energy-dispersive x-ray spectroscopy (EDX) and x-ray diffraction (XRD) patterns revealed that the produced Stellite coating had a lamellar structure consisting of α-Co and ε-Co phases, chromium-rich carbides (Cr23C6 and Cr7C3) and tungsten-containing compounds (W2C). These carbides are responsible for imparting the higher hardness and wear resistance to the Stellite coating. Analysis of microhardness and wear found that higher travel speed of worktable also results in a lower coefficient of friction, specific wear rate coefficient and wears volume and higher microhardness. It can be concluded from this work that micro-PTA process has a capability to selectively deposit a thin and sound quality coating of Stellite on metallic substrates thus providing the techno-economic solution to their wear problems.
Tribological coatings with low coefficients of friction are in high demand by various industries since they can improve machine efficiency and have an environmental impact. A self-lubricating Ni-P-MoS2 composite coating has been successfully deposited on a mild steel substrate by electrodeposition. The effects of MoS2 on the tribological coatings have been investigated. Compared to a pure Ni[single bond]P coating, the Ni-P-MoS2 composite coating exhibited a dramatic reduction in friction coefficient against a bearing steel ball from 0.45 to 0.05. Examination and analysis of the worn surfaces and wear debris, the composite coating showed minimum wear and oxidisation compared to the severe wear and oxidation observed in the pure Ni[single bond]P coating. The evolution of MoS2 particles in sliding wear has been elucidated.
In the present investigation the effect of the substrate dilution on room and high temperature (550 and 700 °C) tribological behaviour of nickel based hardfaced coating deposited by plasma transferred arc onto a grey cast iron was investigated and compared to the uncoated grey cast iron. At room temperature, the wear loss of coatings was independent of the substrate dilution and similar to the grey cast iron. At high temperatures, coating produced with high dilution displayed the highest wear resistance between all the samples. This is attributed to the formation of a protective tribo-layer resulting from the agglomeration of a high amount of oxide debris due to its lower oxidation resistance when compared to the sample produced with low dilution.
Galling as defined by ASTM G40 [1] Terms and Definitions relating to wear and erosion, requires the formation of protrusion (excrescences) from a surface after rubbing contact. However, there are other forms of damage that can occur that can affect the serviceability of a tribosystem. For example, a couple in relative sliding may not form excrescences, but the wear rate can be so large that the test couple would be unsuitable for use. A similar situation can exist if adhesive transfer dominates on the rubbing surfaces.
This paper describes some of the standard galling tests and proposes interpretation of galling results using a multifaceted evaluation matrix that leads to a compatibility rating for a particular sliding couple. The ASTM standard test employs visual inspection of rubbed surfaces to determine if galling occurred. The proposed interpretation uses visual as well as low-powered binocular microscope examination.
The pros and cons of the existing standard tests (ASTM G 98 and G 196) are discussed and it is shown that the proposed rating system solves problems that arise with the present “gall” or not galled” rating system.
It has been reported preiviously that an ordering reaction, the β→β1 transformation, occurs first, followed by a martensitic transformation, β1→β′, on rapid cooling from the β region in Cu-Al binary alloys. The possibility of this transformation process has also been observed in the case of isothermal transformation by means of dilatometric, electric resistance, and specific heat measurements. In order to determine the crystal structure of the β′ martensite with ordered configuration, a powdered specimen containing 24.06 at% Al close to an eutectoid composition was water-quenched from 950°C, and then analyzed by using the diffraction pattern obtained by use of an X-ray diffractometer.The experiments showed the following results, (1) The superlattice lines observed in the diffraction pattern of β′ martensite has proved that the β1→β′ transformation retains the Cu3Al type ordering configuration, Cu3Al type, when rapidly cooled. (2) The crystal structure of the β′ martensite is a distorted hexagonal closepacked structure, in which the (0001) direction makes an angle of about 3° to the normal (0001) plane. The results obtained have been discussed with the martensitic transformations of Cu-Al, Cu-Zn, and Cu-Sn binary alloys and the similarity of the crystal structure and habit plane.
The plasma transferred arc (PTA) technique is currently used to coat the edges of moulds for the glass industry with nickel-based hardfacing alloys. However the hardness and wear performance of these coatings are significantly affected by the procedure adopted during the deposition of coatings. The aim of the present investigation is to study the effect of arc current on the microstructure, hardness and wear performance of a nickel-based hardfacing alloy deposited on gray cast iron, currently used in molds for the glass industry. Microstructure, hardness and wear assessments were used to characterize the coatings. Electron probe micro analysis (EPMA) mapping, scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDAX) and X-ray diffraction (XRD) were used to characterize the microstructure of the deposits. The effect of post weld heat treatment (PWHT) on the microstructure and hardness was also studied. The typical microstructure of the coatings consists of dendrites of Ni–Fe, in the FCC solid solution phase, with interdendritic phases rich in Cr–B, Ni–Si and Fe–Mo–C. Increasing the arc current reduces the proportion of porosity and hardness of the coatings and modifies their composition due to the increasing dilution of the cast iron. The partial melted zone (PMZ) had a typical white cast iron plus martensite microstructure, while the heat affected zone (HAZ) had only a martensite structure. The wear tests showed decreasing wear resistance with decreasing hardness of the coatings. PWHT reduces the hardness of the PMZ and HAZ but does not significantly alter the hardness of the bulk coating.
The effect of solute atoms on sliding wear was studied by alloying OFHC copper with chromium, silicon and tin. The hardness was found to increase linearly with the atomic solute content although the rate of hardening was different for different solutes.Microscope observations show that the principal mode of wear is indeed delamination. The results further show that both the wear rate and the friction coefficient are reduced when the solute content is increased. The reduction in the friction coefficient is a consequence of reduced plowing contribution to the tangential component of the surface traction. Both the increase in hardness and the decrease in the friction coefficient reduce the wear since both affect the subsurface deformation rate and consequently the crack nucleation rate. The lower coefficient of friction also reduces the crack propagation rate and the thickness of the wear sheets.
A new aluminum bronze material with aluminum content over the solubility limit and several trace elements, Cu–14Al–X alloy (X is trace elements), has been developed for drawing dies. The mechanical properties such as hardness, tensile strength and impact toughness were evaluated experimentally. The friction and wear behavior of the material was investigated under boundary lubrication conditions. The experimental results demonstrated that the developed alloy possessed higher tensile strength and hardness, lower friction coefficient and wear rate, compared to currently used aluminum bronzes, therefore it is expected to replace conventional iron-based materials that are commonly used for drawing dies. With the excellent anti-friction property and high carrying capacity, the new material, Cu–14Al–X alloy, will be able to provide precision drawing dies.
A Cu-12wt.%Al eutectoid composition binary alloy was tested for friction and wear in three conditions designed to provide (1) a eutectoidal microstructure (treatment E), (2) a martensitic microstructure (treatment M) and (3) an electron-beam-melted surface (treatment EB). Polished blocks of the alloy were wear tested unlubricated against AISI 52100 steel rings at a 10 N load and 20 cm s−1 velocity in an argon gas environment. Both EB and M treatments gave lower block wear than the E heat treatment. All three showed transfer of material to the steel rings. Friction break-in characteristics varied with heat treatment. The martensitic microstructure, while lower in microindentation hardness, had a lower block wear volume. Electron beam melting of this alloy did not seem to improve performance any further than the quench used to produce martensite.
Phase transformations in a Cu-AI alloy which was in the martensitic state were examined by the use of differential thermal analysis. The influence of the speed of temperature changes on the character of the phase transformation was determined. The new sequence of phase transformations in martensite is discussed and related to the physical properties (the “shape memory effect”). Characteristic temperatures and heats of transformation in the alloy are also estimated.
The crystal structure of β' martensite in a Cu–11.7% alloy has been studied by transmission electron microscopy and electron diffraction. The structure has a monoclinic lattice, whose unit consists of 6 close-packed layers having a superlattice. It can also be described as an orthorhombic lattice having lattice constants of a=4.49 Å, b=5.19 Å, c=38.2 Å, (a: b: c=√3: 2: 18√\tfrac23), and consisting of 18 layers AB'CB'CA'CA'BA'BC'BC'AC'AB', where the positions of atoms in each layer (ab plane) are
(A) Al:(00); Cu:(0\tfrac12), (\tfrac12\tfrac14), (\tfrac12\tfrac34), (A')=(A)+(\overrightarrow0\tfrac12),
(B)=(A)+(\overrightarrow\tfrac130), (B')=(B)+(\overrightarrow0\tfrac12),
(C)=(A)+(\overrightarrow\tfrac230), (C')=(C)+(\overrightarrow0\tfrac12),
where (A)+(\overrightarrow\tfrac130) means that all the atoms in layer `A' are displaced by the amount of vector (\overrightarrow\tfrac130).
The application of response surface methodology was highlighted to predict and optimize the percentage of dilution of iron-based hardfaced surface produced by the PTA (plasma transferred arc welding) process. The experiments were conducted based on five-factor five-level central composite rotatable design with full replication technique and a mathematical model was developed using response surface methodology. Furthermore, the response surface methodology was also used to optimize the process parameters that yielded the lowest percentage of dilution.
A modified single melt technique involving joint charign was developed for preparation of aluminium bronze, Cu-14%Al-X(mass fraction) alloy, which could be used as die materials. The mechanical properties and wear behaviour of the developed alloy under boundary-lubrication conditions was investigated. The results demonstrate that all the phases disperse homogenously in the bronze matrix with a significant amount of discrete and spherical brittle and hard γ2 phase, moreover, the dispersed κ phase are the dominant factor that improves the anti-deformation properties of the soft matrix, after a solution treatment at 920 °C for 2 h and followed by aging at 580 °C for 3 h, thus remarkably improves the mechanical roperties and wear resistance of the developed alloy. The Cu-14% Al-X alloy can be used as materials for static precise stretching and squeezing dies.
Unlubricated rolling-sliding wear tests of as-received and electron beam surface melted complex aluminium bronze, CA104, against hardened En19 steel have been carried out. Test samples have been examined using optical microscopy, scanning electron microscopy and microhardness measurements. It is found that both adhesive wear and delamination wear occur in the wear process and the wear debris forms in two ways. Two types of structures exist in the wear debris, which are related to a deformed and a highly deformed subsurface structure in the tested samples. Electron beam surface melting improves the wear resistance of the material but the wear mechanisms involved have not been fundamentally changed.
The influence of the disordered (Cu)-α phase in the isothermal aging kinetics of the Cu–19 at.%Al alloy was studied using microhardness measurements, optical and scanning electron microscopy and X-ray diffractometry. The results indicate that the β′→(α+γ1) decomposition reaction rate increases with the increase of the temperature in the range between 150 and 500°C and at 600°C the reaction is delayed by the α phase precipitation. The value obtained for the activation energy indicates an interface diffusion controlled reaction.
Control of dilution is important in hardfacing, where low dilution is typically desirable. At present, most fabrication industries
use shielded metal are welding, gas metal arc welding, gas tungsten arc welding and submerged are welding processes for hardfacing
purposes. In these processes, the percentage of the dilution level is higher, ranging between 10% and 30%. In Plasma Transferred
Arc (PTA) hardfacing, a solidified metallurgical bond between the deposit and the substrate is obtained with minimum dilution
(less than 10%). This paper highlights the application of response surface methodology to predict and optimize the percentage
of the dilution of a cobalt-based hardfaced surface produced by the PTA process. Experiments were conducted based on a fully
replicable five-factor, five-level central composite rotatable design and a mathematical model was developed using response
surface methodology. Furthermore, the response surface methodology was used to optimize the process parameters that yield
the lowest percentage of dilution.
The growing awareness of environmental issues and the requirements to establish solutions diminishing the impact on working environment as well as external environment has initiated ever increasing efforts to develop new, environmentally benign tribological systems for metal forming. The present paper gives an overview of these efforts substituting environmentally hazardous lubricants in cold, warm and hot forging as well as sheet forming and punching/blanking by new, less harmful lubricants and furthermore describes other measures directed towards the same goal such as development of anti-seizure tool materials and coatings and application of structured workpiece and tool surfaces.
Detailed examination of copper specimens after sliding against 440 C steel in liquid methane at speeds up to 25 m s−1 and loads of up to 2 kg showed the metal comprising the wear surface to possess a fine cell recrystallized structure. Wear proceeded by the plastic shearing of metal in this near surface region without the occurrence of visible metal transfer. A dynamic balance between the intense shear process at the surface and the nucleation of recrystallized grains was proposed to account for the behavior of the metal at the wear surface. Sliding wear experiments were also conducted on Ag, Cu-10% Al, Cu-10% Sn, Ni and Al. The results were correlated with published hot-working observations and recrystallization kinetics. It was found that low wear and the absence of heavy metal transfer were associated with those metals observed to undergo recrystallization nucleation without prior recovery.
In dry sliding wear dynamic recrystallization gives a better understanding than grain boundary sliding and fatigue of the process near the contact zone. The process explains the low value of the deformation measured by grain thickness reduction and the absence of visible deformation marks in the case of low melting materials. Dynamic recrystallization explains the almost total consumption of the friction energy by the plastic process. It is also possible to compute the geometry of the worn material in a wear test. This phenomenon is proved experimentally using a copper pin sliding against an SAE 1045 steel ring. Pins of both single crystal and polycrystalline copper were used. The structure was observed by examining thin foils of the material taken from near the contact zone in an electron microscope.