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a Micro crevice corrosion occurring at the interface between an inclusion and the metal matrix after PDP testing and 1 week immersion in 3.5 wt% NaCl. b Box plots of corrosion potential and potential breakdown values extracted from PDP measurements of passivated and electrochemically depassivated SS samples (n = 3, error bars represent absolute error at 95% C.I.). (Inset) Examples of typical PDP measurements recorded for prepared SS 444 substrates. The naturally passivated sample (black curve) shows robust corrosion resistance by reaching the transpassive region while the depassivated and mechanically grown film (red curve) showed premature pitting. SEM images of (c) the micro leaf-like corrosion observed ex situ polarization of the depassivated sample. The inset shows the TiN inclusion directly in the center of the localized corrosion. d A stable oxide nucleated inclusion ex situ polarization
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Titanium has been added to ferritic stainless steels to combat the detrimental effects of intergranular corrosion. While this has proven to be a successful strategy, we have found that the resulting Ti-rich inclusions present on the surface play a significant role in the initiation of other forms of localized corrosion. Herein, we report the effect...
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High resolution analysis of corrosion processes on stainless steels is a challenging task. The application of local electrochemical techniques such as scanning electrochemical microscopy (SECM) has opened new possibilities for the detection of corrosion products and activity on metallic surfaces. However, due to its stochastic nature, the analysis...
Citations
... 41 F I G U R E 4 Types of corrosion of titanium and its alloys. [57][58][59][60][61] critical factor in metallic biomaterials. In the presence of body fluids with a pH close to neutral, these materials exhibit exceptionally low corrosion rates, which can be difficult to evaluate experimentally. ...
There are several enviable attributes of titanium and its alloys that contribute to their popularity in biomedical devices and equipment, including their rather low modulus, excellent corrosion resistance, and biocompatibility, good machinability, formability, and strength comprehensive impact and fatigue. Nevertheless, titanium and its alloys do not meet all medical requirements due to its unique properties and alloys, so surface modifications must be made to enhance mechanical, chemical, and biological characteristics. As a review of biomedical engineering, this article discusses specific polymers for coating applications as well as various polymer coatings for functionalization improvements. The versatility of biopolymer coatings makes them extremely appropriate for a broad range of biological uses. To enhance the engineering of tissue and drug delivery, this study summarized and analyzed the most recent advances in biopolymer coatings. Surface qualities of polymer coatings can be adjusted to meet specific criteria for various biomedical applications or integrated with new capabilities. Moreover, polymer coatings containing different inorganic ions can enhance the growth of tissue, proliferation of cells, healing, as well as the transfer of biomolecules, like active molecules, agents of antimicrobial, factors of growth, and medications.
Highlights
Surface modification avenues of Ti materials as orthopedic replacements are critically reviewed.
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... The addition of Ti has been used to suppress the formation of Cr-rich carbides (Cr 23 C 6 ), retarding the formation of retained austenite, and further enhancing the strength without severely decreasing the toughness [23]. The presence of Ti(C,N) artifacts from this microaddition has been reported on alloys 600, 690, and stainless steel 444 inducing localized corrosion and cracking by functioning as stress concentrators [24][25][26][27]. Several works have also found these types of inclusions in M13Cr, however, their influence on the passivation and pit initiation has not been extensively studied [23,[28][29][30]. ...
... The presence of cubic inclusions were dispersed along the previous austenite grain boundaries and were shown to appear in three forms: square Ti(C,N), square Ti(C,N) with nucleus, and Ti(C,N) stringers [25,27]. The material studied comprised of Ti(C,N) inclusions of all these morphologies. ...
... This contrasts the findings of Srivastava et al. [44] on stainless steels 301 and 316, who inferred these inclusions function as cathodic sites, however no SKPFM has been performed to conclusively prove this. This assertion has also been extended to stainless steel 444 by Gateman et al. [27] and alloy 690 TT by Meng et al. [25]. For M13Cr, the SKPFM results unequivocally demonstrate their anodic nature. ...
... The addition of Ti has been used to suppress the formation of Cr-rich carbides (Cr 23 C 6 ), retarding the formation of retained austenite, and further enhancing the strength without severely decreasing the toughness [23]. The presence of Ti(C,N) artifacts from this microaddition has been reported on alloys 600, 690, and stainless steel 444 inducing localized corrosion and cracking by functioning as stress concentrators [24][25][26][27]. Several works have also found these types of inclusions in M13Cr, however, their influence on the passivation and pit initiation has not been extensively studied [23,[28][29][30]. ...
... The presence of cubic inclusions were dispersed along the previous austenite grain boundaries and were shown to appear in three forms: square Ti(C,N), square Ti(C,N) with nucleus, and Ti(C,N) stringers [25,27]. The material studied comprised of Ti(C,N) inclusions of all these morphologies. ...
... This contrasts the findings of Srivastava et al. [44] on stainless steels 301 and 316, who inferred these inclusions function as cathodic sites, however no SKPFM has been performed to conclusively prove this. This assertion has also been extended to stainless steel 444 by Gateman et al. [27] and alloy 690 TT by Meng et al. [25]. For M13Cr, the SKPFM results unequivocally demonstrate their anodic nature. ...
... For this reason, in this study, we propose enriching developed FeCrAl-based steels with Ti and V (maximum 1 and 0.5 wt.%) and Y 2 O 3 . These metallic elements are also well known as responsible for steels microstructure strengthening (Vanadium [16,17]) and improving their corrosion resistance (Titanium [18]). The development of oxide dispersion-strengthened (ODS) alloys has been studied for many years so far with excellent results [19,20]. ...
... However, recent findings with respect to solid-state heat treatments indicate that unreacted chromium can segregate around these precipitates for which IGC is enabled again [27][28][29]. Moreover, titanium inclusions may initiate other selective corrosion phenomena such as pitting corrosion [30,31]. In addition, WM grain boundaries occupied by titanium precipitates are prone to dissolution and, thus, the initiation of special forms of IGC which impair the structural integrity of the component [31]. ...
Ferritic stainless steels are prone to grain coarsening and precipitation of chromium-rich grain boundary phases during fusion welding, which increase intergranular corrosion susceptibility. State-of-the-art techniques to overcome these challenges mainly feature heterogeneous nucleating agents with regard to grain coarsening or alternating alloy concepts as well as post-weld heat treatments as for restoration of intergranular corrosion resistance. The present investigation seeks to depart from these traditional approaches through the use of a tailored heat input during pulsed laser beam welding by means of free-form pulse shaping. Grain size analysis using electron backscatter diffraction shows a substantial reduction of grain size as compared to continuous-wave lasers due to a distinctive columnar to equiaxed transition. Moreover, phase analyses reveal the overcoming of chromium carbide precipitation within the heat-affected zone. As corrosion tests demonstrate, intergranular attack is therefore concentrated on the weld metal. In comparison to continuous-wave laser beam welding, intergranular corrosion susceptibility is substantially reduced for very short pulse durations. From these results, it can be derived that pulsed laser beam welding using free-form pulse shaping enables direct control of heat input and, thus, tailored grain growth and precipitation formation properties.
... In terms of inclusion-induced localized corrosion, we see amongst the major challenges in the next steps of development as gaining the ultra-high resolution figures and element distribution results of the micro-regions, and of realizing the accurate judgment for the preferential corrosion position of inclusion or local matrix when it is infinitely close to the initial stage. The main driver behind this is based on the discovery that preferential dissolution of inclusions or adjacent matrix also show selective in previous work, indicating that the future studies on inclusion-induced corrosion is expected to be further carried out at the nano-to-atomic scale [100][101][102][103] . What's more, the conductivity of target inclusion and the potential difference between inclusions and matrix, and the micro-defects at the contact sites are the prerequisites for triggering localized corrosion in an aggressive condition. ...
Localized corrosion triggered by inclusions is prone to metallic material failure. Except for chemical dissolution of some special inclusions, the principle of galvanic coupling is the most acceptable theory to explain the above corrosion damage mechanism over the past decades. Still, controversies continue to present, in particular, mounting recent evidence obtained by advanced technologies emphasizes the limitations of previous entrenched idea and discloses unexpected results. Here, we review relevant recent studies and carefully summarize their similarities and differences to reduce the knowledge gap between inclusion-triggered localized corrosion and material design, whilst the source of typical inclusions is treated and discussed.
... TiCN nanoparticles could have reacted in the steel melt, giving rise to secondary precipitates of the above mentioned compositions. As it happens in (c), TiN precipitates found in steel usually appear as rectangular inclusions of micrometer size [23][24]. ...
Novel processing technologies have allowed the reinforcement of several steel grades and alloys through the fine dispersion of different types of particles. However, the addition of ceramic particles in the steel melt causes agglomeration and coarsening phenomena. For this reason, little research has been carried out to add ceramic particles in steel in the traditional steelmaking process. Here we report a hardened and tempered steel grade that is reinforced for the first time through the addition of ceramic nanoparticles, such as TiCN and SiC, into the steel melt at laboratory scale. The results obtained from the tensile tests and hardness measurements reveal the mechanical behaviour of the steel grade is enhanced after the addition of the nanoparticles. KEYWORDS: Hardened and tempered steel; Nanoparticle; Laboratory scale casting; Microstructure; Grain refinement; Solid solution hardening; Mechanical properties
... Nowadays, most corrosion removal methods are based on the use of highly concentrated substances, such as phosphoric acid, hydrochloric acid, sulfuric acid, etc. [3][4][5]. These components are chemically aggressive substances that excessively destroy metal surfaces [6,7]. ...
In this article, we presents the synthesis and research of a tool for removing metal inclusions from the surface of car paint coatings. The optimal composition of the product was determined, which includes sodium laureth sulfate, citric acid, sulfosalicylic acid, hydrogen peroxide and water. As a result of the conducted studies, a connection was established between the composition and the physicochemical, surface-active properties of the developed agent. Approbation of this tool was carried out, which confirmed its effectiveness and showed that within 30–45 s after applying the developed tool, not only are metal inclusions on the surface of car paint coating removed but also mineral contaminants in the form of sand, earth, clay and other particles. The aim of the work was to develop and optimize a method for obtaining a low-toxicity, highly effective agent for removing metal inclusions from the surface of car paint coatings and to investigate its effectiveness, as well as its physicochemical, optical and surface-active properties.
... In addition to the mechanisms presented beforehand, another selective corrosion mechanism involved in the dissolution of AISI 430Ti weld metal could be identified. As reported by Gateman et al. [29] for bulk AISI 444, titanium precipitates-in particular titanium nitrides-may affect the localized corrosion of stainless steels as they represent a discontinuity in the passive layer. As can be seen in Figure 6b, one such titanium nitride could be identified on top of the welding bead surface through EDS (cf. Figure 6c). ...
... In congruence to the findings of Gateman et al. [29], selective corrosion can be identified in the surrounding matrix of the precipitate due to galvanic coupling. Despite the comparatively small spatial propagation, these findings show that selective corrosion phenomena of titanium nitrides can also occur within the weld metal of stabilized FSS, for which their corrosion resistance is impaired. ...
... Neither of these values can be reached in a laser-welded condition following corrosive attack, which emphasizes the cataclysmic character of intergranular attack. In congruence to the findings of Gateman et al. [29], selective corrosion can be identified in the surrounding matrix of the precipitate due to galvanic coupling. Despite the comparatively small spatial propagation, these findings show that selective corrosion phenomena of titanium nitrides can also occur within the weld metal of stabilized FSS, for which their corrosion resistance is impaired. ...
The intergranular corrosion susceptibility of ferritic stainless-steel weldments is strongly dependent on chromium carbide precipitation phenomena. Hence, stabilization is widely used to mitigate the aforementioned precipitation. In contrast, stabilization has proved ineffective to fully prevent intergranular corrosion due to segregation of unreacted chromium during solid-state heat-treatments. To analyze the precipitation behavior of 17 wt.-% chromium ferritic stainless steels during laser welding, sheets of unstabilized and titanium-stabilized ferritic stainless steels were welded in a butt joint configuration and characterized with special consideration of precipitation behavior by means of transmission electron microscopy. While unstabilized ferritic stainless steels exhibit pronounced chromium precipitate formation at grain boundaries, titanium-stabilization leads to titanium precipitates without adjacent chromium segregation. However, corrosion tests reveal three distinctive corrosion mechanisms within the investigated ferritic stainless steels based on their inherent precipitation behaviors. In light of the precipitation formation, it is evident that immersion in sulfuric acid media leads to the dissolution of either grain boundaries or the grain boundary vicinity. As a result, the residual mechanical strength of the joint is substantially degraded.
... Yet, FSS can exhibit specific forms of localized corrosion such as pitting corrosion (PC) and intergranular corrosion (IGC) [7,9], which hinder a widespread application of these grades. Pitting corrosion is either initiated by the penetration of the passive layer through chlorine ions [10] or at local inclusions such as oxides, sulfides or nitrides [11][12][13][14][15]. Intergranular corrosion, on the other hand, is formed and proceeds along sensitized regions adjacent to grain boundaries, which are depleted in chromium, i.e., whose chromium content has fallen below 12 wt. ...
... Yet, a number of studies can demonstrate the inefficiency of this approach due to the segregation of unreacted chromium around primary precipitates such as titanium carbide [28][29][30]. Moreover, titanium carbides (TiC) or nitrides (TiN) act as inclusions within the surrounding matrix and therefore, again, promote selective corrosion phenomena [14,15]. Along with these observations, intergranular corrosion can also be identified in unstabilized and Ti-stabilized FSS when welded with a fiber-laser under the utilization of very low energy inputs [31]. ...
Ferritic stainless steels are prone to localized corrosion phenomena such as pitting corrosion or intergranular corrosion, in particular when jointed by fusion welding processes. State-of-the-art techniques to avoid intergranular corrosion mainly consist of alternating alloy concepts or post-weld heat-treatments—all of which are associated with increased production costs. Hence, the present investigation seeks to introduce a novel approach for the inhibition of intergranular corrosion in ferritic stainless steel welds through the use of high-speed laser cladding. Here, vulnerable sites prone to intergranular corrosion along the weld seam area are coated with a chemically resistant alloy, whereby an overlap is achieved. Optical and electron microscopy as well as computer tomography and tensile tests reveal that the detrimental effects of intergranular corrosion in both stabilized and unstabilized ferritic stainless steel are substantially reduced. In addition to that, the effects of varying overlap widths on the identified corrosion phenomena are studied. Moreover, the resulting dilution and precipiation phenomena at the clad–sheet interface are thoroughly characterized by electron backscatter diffraction and energy dispersive X-ray spectroscopy, whereby interrelationships to corrosion resistance can be drawn. As a result of this investigation, the number of techniques for the inhibition of intergranular corrosion is enlarged, and substantial cost-saving potentials in the manufacturing industry are unlocked.
