Search Results (37)

Nowadays, Thin Dense Chromium (TDC) coatings are being industrially used in rolling bearings applications due to their claimed advantages such as high hardness, low wear, and good corrosion resistance. However, despite their broad commercial use, very little has been published in the open scientific literature regarding their microstructure, nanomechanical, and tribological properties. In this paper, TDC coatings with a thickness of about 5 µm were deposited by a customized electrochemical process on ASTM 52100 bearing steel substrates. Surface microstructure and chemical composition analysis of the TDC coatings was carried out by scanning electron microscopy and atomic force microscopy. The results revealed a coating with a dense, nodular, and polycrystalline microstructure. Unlike standard electrodeposited “Hard Chromium” coatings, TDC coatings show no presence of micro/nano-cracks, likely contributing to their superior corrosion resistance. The nanomechanical behavior, studied by nanoindentation as a function of penetration depths, exhibits a pronounced size effect near the coating surface that can be linked to the nodular microstructure. A hard surface with hardness H_IT 14.9 ± 0.5 GPa and reduced elastic modulus E_r = 216.8 ± 3.9 GPa was observed. Tribological characterization under the presence of lubricants was performed by two single-contact tribometers using coated and uncoated steel balls against flat steel substrates. An in-house fretting wear rig was used to measure the lubricated friction coefficient in pure sliding conditions, whilst the friction performance in rolling/sliding lubricated conditions was evaluated using a WAM test rig. In pure sliding, TDC/TDC contacts show ~13% lower friction than for steel. Under rolling/sliding conditions with 5% sliding, the traction coefficient of TDC/TDC coating contact was at least 20% lower than that for steel/steel contact. The tribological results obtained in various contact conditions demonstrate the benefits of applying TDC coatings to reduce bearing friction. Full article

This review covers the literature that is currently accessible, as well as emerging research into the performance of NiTi-based alloys exposed to corrosive environments in both engineering and medical applications. It provides an overview of the state-of-the-art research in the study of tribocorrosion of Ni-rich NiTi alloy by highlighting significant discoveries, research approaches, and future research directions following the limited reviews on tribocorrosion in the past decade. The practical impacts, as well as the economic implications of tribological applications on daily life, coupled with the increasing failures of metals and biomaterials, make it imperative to investigate tribocorrosion and update the subject area on the recent focus. Tribocorrosion is commonly observed on the surface of different metals, including NiTi alloys, such as NiTiNOL60 (60 wt.% Ni and 40 wt.% Ti), which possess unique properties applicable across various engineering and biomedical fields. In its application, the material experiences wear due to the depassivation of tribofilms caused by relative motion (sliding, fretting, or impact) in aggressive environments, including corrosive mediums, high temperatures, and pressures. This study elucidates the synergistic interactions between mechanical wear, corrosion, and their associated tribocorrosion mechanisms in corrosive media. Full article

The nickel-based alloy Inconel 600, strengthened by solution treatment, finds extensive application as a heat exchange pipe material in steam generators within nuclear power plants, owing to its exceptional resistance to high-temperature corrosion. However, fretting corrosion occurs at the contact points between the pipe and support frame due to gas–liquid flow, leading to wear damage. This study investigates the fretting wear behavior and damage mechanism of the nickel-based alloy Inconel 600 and 304 stainless steel friction pairs under point contact conditions in a water environment. Characterization was performed using laser confocal scanning microscopy and scanning electron microscopy equipped with energy-dispersive spectroscopy. Results indicate that the friction coefficient remains consistent across different chloride ion concentrations, while the wear volume increases with increasing chloride concentrations. Notably, friction coefficient oscillations are observed in the gross slip regime (GSR). Moreover, the stability of the oxide layer formed in water is compromised, diminishing its protective effect against wear. In the partial slip regime (PSR), friction coefficient oscillations are absent. An oxide layer forms within the wear scar, with significantly fewer cracks compared to those within the oxide layer in the GSR. It is worth noting that in GSR, the friction coefficient oscillates. Full article

The TC4 (Ti-6Al-4V) alloy has problems such as low material hardness, poor wear resistance, and abnormal sensitivity to adhesive wear and fretting wear. In this study, we used graphene-reinforced Ti/BN composite coatings prepared on the surface of the TC4 alloy by argon arc cladding technology. We explored the optimal content of graphene to improve its hardness and wear resistance. The physical phases and microstructures of the coatings were analyzed using an X-ray diffractometer, metallurgical microscope, and scanning electron microscope. Microhardness and wear properties of the cladding coating were measured by a Vickers hardness tester and a universal friction and wear tester. The incorporation of graphene resulted in a transformation of the reinforcing phase in the coating from TiN to Ti(N, C). The C element in the molten pool was substituted with the N element in an unending solid solution, resulting in the formation of Ti(N, C) through intermittent nucleation. As the amount of graphene in the molten pool increases, the concentration of carbon (C) also increases. This leads to the continuous growth of Ti(N, C) particles, resulting in a coarser coating structure and a decrease in coating performance. When the graphene content is 5 wt.%, the microstructure refinement of the coating is the most obvious, the microhardness is 900 HV_0.2, which is 3 times higher than that of the matrix, and the wear rate is 4.9 × 10⁻⁵ mm³/(N·m), which is 4.9 times higher than that of the matrix. The wear mechanism of the coating is primarily abrasive wear with some slight adhesive wear. Full article

This work investigated the wear behavior of ultrafine-grained Ti₆₅Nb_23.33Zr₅Ta_1.67Fe₅ (at.%, TNZTF) and Ti₆₅Nb_23.33Zr₅Ta_1.67Si₅ (at.%, TNZTS) alloys fabricated by high-energy ball milling and spark plasma sintering. Wear tests were conducted in a simulated physiological solution under both reciprocating sliding and fretting wear conditions with different loads, frequencies, and stroke lengths. The microstructures, mechanical properties, and anti-wear properties of the investigated alloys were characterized. The results showed that the TNZTF and TNZTS alloys had much less wear volume than the commonly used Ti-6Al-4V (TC4) alloy and commercially pure titanium (CP-Ti). The TNZTF and TNZTS alloys exhibited much more smooth wear surfaces and shallower wear scars compared with TC4 and CP-Ti. The investigated alloys exhibited different wear mechanisms under the reciprocating sliding wear conditions, while they were similar under the fretting wear conditions. Compared with TC4 and CP-Ti, the fabricated TNZTF and TNZTS alloys showed a substantially higher wear resistance, owing to their ultrafine-grained microstructure and superior hardness. Additionally, the addition of Nb and Zr further enhanced the wear resistance by forming a protective Nb₂O₅ and ZrO₂ oxide film. This work provides guidance for designing new biomedical titanium alloys with excellent wear resistance. Full article

To address friction and wear challenges in dry contacts, manufacturers often employ self-lubricating materials. Graphite and its derivatives stand out as particularly suitable due to their exceptional tribological properties. However, under intense friction conditions, graphite can experience a decline in lubricating efficiency due to severe abrasive wear. This abrasive damage results in elevated activated carbon surfaces with increased surface energy, fostering greater adhesion between sliding surfaces. The low friction coefficient of graphite is not an inherent property but rather a consequence of water vapor adsorption by the material. Beyond 150 °C, desorption of the vapor occurs, leading to a transition in the friction coefficient from µ = 0.1 to µ = 0.6. To address this issue, impregnation solutions for self-lubricating materials have been developed, with various compositions tailored to specific objectives. Common types include molybdenum disulfide, soft metals and polymers. In this predominantly experimental study, the impact of polymer impregnation on the evolution of friction force and wear rate in graphite material bearings subjected to a dry fretting contact under severe thermal stresses at 270 °C was investigated. Additionally, the mechanical stresses in the bearings throughout different phases of our tests were analyzed using a numerical model. Full article

The rise in electrification has considerably increased the demand for high-efficiency and durable electrical contact materials. Carbon nanoparticles (CNP) are a promising coating material due to their intrinsic transport properties (thus minimizing the impact on conductivity), their proven solid lubricity (potentially improving tribological performance), and their hydrophobic wetting behavior (potentially providing atmospheric protection). In this study, carbon nanotube and nanohorn coatings are produced via electrophoretic deposition on silver-plated surfaces, followed by tribo-electrical and wetting characterization. The proposed coatings do not negatively affect the conductivity of the substrate, showing resistance values on par with the uncoated reference. Tribo-electrical characterization revealed that the coatings reduce adhesive wear during fretting tests while maintaining stable and constant electrical contact resistance. Furthermore, CNP-coated surfaces show a hydrophobic wetting behavior toward water, with graphite and carbon nanotube (CNT) coatings approaching super-hydrophobicity. Prolonged exposure to water droplets during sessile drop tests caused a reduction in contact angle (CA) measurement; however, CNT coatings’ CA reduction after five minutes was only approximately 5°. Accordingly, CNP (specifically CNT) coatings show auspicious results for their application as wear and atmospheric protective barriers in electrical contacts. Full article

AISI 316L stainless steel has received considerable attention as a common material for key ball valve components; however, its properties cannot be improved through traditional phase transformation, and fretting wears the contact interface between valve parts. A carburized layer was prepared on the surface of AISI 316L stainless steel by using double-glow low-temperature plasma carburization technology. This study reveals the effect of double-glow low-temperature plasma carburization technology on the fretting wear mechanism of AISI 316L steel under different normal loads and displacements. The fretting wear behavior and energy dissipation of the AISI 316L steel and the carburized layer were studied on an SRV-V fretting friction and wear machine with ball–plane contact. The wear mark morphology was analyzed by using scanning electron microscopy (SEM), the phase structure of the carburized layer was characterized with X-ray diffractometry (XRD), and the wear profile and wear volume were evaluated with laser confocal microscopy. The carburized layer contains a single Sc phase, a uniform and dense structure, and a metallurgically combined matrix. After plasma carburizing, the sample exhibited a maximum surface hardness of 897 ± 18 HV_0.2, which is approximately four times higher than that of the matrix (273 ± 33 HV_0.2). Moreover, the surface roughness was approximately doubled. The wear depth, wear rate, and frictional dissipation energy coefficient of the carburized layer were significantly reduced by up to approximately an order of magnitude compared with the matrix, while the wear resistance and fretting wear stability of the carburized layer were significantly improved. Under different load conditions, the wear mechanism of the AISI 316L steel changed from adhesive wear and abrasive wear to adhesive wear, fatigue delamination, and abrasive wear. Meanwhile, the wear mechanism of the carburized layer changed from adhesive wear to adhesive wear and fatigue delamination, accompanied by a furrowing effect. Under variable displacement conditions, both the AISI 316L steel and carburized layer mainly exhibited adhesive wear and fatigue peeling. Oxygen elements accumulated in the wear marks of the AISI 316L steel and carburized layer, indicating oxidative wear. The fretting wear properties of the AISI 316L steel and carburized layer were determined using the coupled competition between mechanical factors and thermochemical factors. Low-temperature plasma carburization technology improved the stability of the fretting wear process and changed the fretting regime of the AISI 316L steel and could be considered as anti-wearing coatings of ball valves. Full article

β-titanium (β-Ti) alloys are used in various biomedical applications, especially for orthopedic implants, due to their superior biocompatibility, excellent corrosion resistance, and enhanced mechanical properties. However, the inferior tribological properties of β-Ti alloys lead to fretting wear and a strong tendency to seize, which is a major concern in orthopedic applications involving continuous friction. This work aims to address this issue by incorporating biocompatible nitrides in Ti-Nb-Zr-Ta (TNZT) β-Ti alloys. TNZT composites comprising 2 wt.% of biocompatible nitrides (TiN, NbN, ZrN, and TaN) were prepared using high-energy ball milling followed by spark plasma sintering. All the nitrides improved the hardness and wear resistance of TNZT alloys and showed excellent biocompatibility. TNZT-2 wt.% TiN showed the average highest hardness of 311.8 HV and the lowest coefficient of friction of 0.659, suggesting the highest efficiency of TiN in improving the tribological performance of TNZT alloys. The underlying mechanisms behind the superior performance of nitride-reinforced TNZT composites are discussed in detail. The effect of TiN concentration was also studied by preparing TNZT composites with 5 and 10 wt.% TiN, which showcased a higher hardness of 388.5 HV and 444.3 HV, respectively. This work will aid in producing superior β-Ti alloys for advanced orthopedic applications. Full article

This paper investigated the fretting failure of axial thrust steel bearings as per ASTM 4170 in the presence of anti-fretting pastes used in process industries. The pastes were differentiated based on the content of additives in them. The results indicated that the paste containing the additive package of copper, molybdenum disulfide, and graphite exhibited excellent anti-fretting properties (75–80% less bearing race mass loss) as compared with other lubricating pastes that contained only graphite/molybdenum disulfide and nickel as primary additives. There was less surface damage to the bearing races in the lubricating paste containing copper, graphite, and molybdenum disulfide. The machine vision images of the false brinelling indicated that the average area of false brinelling on the bearing races with the paste containing copper, molybdenum disulfide, and graphite was 2.537 ± 0.623 mm², while that of the other pastes containing graphite/molybdenum disulfide and nickel as primary additives were 4.504 ± 0.566 mm² and 4.914 ± 0.621 mm², respectively, indicating 50% less false brinelling area in the paste containing copper, molybdenum disulfide, and graphite as compared with the paste containing graphite/molybdenum disulfide and nickel. An asymmetric wear pattern was also observed in the thrust bearings used during the tribo test. Surface characterizations indicated the formation of wear debris, plastic deformations, and surface cracks during the tribo tests. The physico-chemical properties of the lubricating pastes such as the viscosity and work penetration properties played an important role in controlling the failure of the bearings due to fretting. Full article

This paper investigates the effect of ultrasonic surface rolling (USR) on the fretting wear properties of the 7075 aluminum alloy. A white light interferometer, Vickers hardness tester, and X-ray diffractometer were employed to comparatively analyze the variations in surface roughness, hardness. and grain size before and after the USR treatment. The fretting tests were carried out under oil lubricated and dry fretting conditions, using a ball-on-flat contact tangential fretting tester. The worn surface morphology, wear debris, and chemical composition were analyzed using an optical microscope (OM), a scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS), etc. The results revealed that after USR treatment, the surface roughness was reduced by 90%, the hardness was increased by 13HV, and the grains were refined. Moreover, the wear was reduced under oil lubrication conditions but increased under dry fretting conditions. It can be concluded that the microstructure and mechanical properties of the 7075 aluminum alloy surface can be enhanced by the USR treatment. The improved fretting performance in oil should be attributed to the increased surface hardness, which helps reduce abrasive wear and plastic deformation. However, under dry fretting conditions, the wear was increased due to the presence of hard debris particles that peel off from the USR-treated surface, leading to aggravated abrasion. Full article

Due to the excellent properties of Ti (C,N)-based ceramics, such as high hardness, excellent wear resistance, exceptional thermal deformation resistance, and sound chemical stability, they have been widely used in cutting tools or molds. Thus, revealing their tribological behavior against hard materials is of great significance. Some studies have reported the tribological behavior of Ti(C,N)-based cermets and hard cermets, but so far, the effects of Mo₂C additions on the frictional properties of Ti(C,N)-based cermets are still unclear. In this study, Ti(C,N)-10WC-1Cr₃C₂-5Co-10Ni-x Mo₂C cermets (x = 4, 6, 8, 10 and 12 wt.%) were sintered using a vacuum hot-pressing furnace. Furthermore, the core–rim morphologies of the sintered samples were observed in SEM images. Then, the wear resistance of the cermets was studied against a Si₃N₄ ball at a 50 N load using the fretting wear test. Finally, the wear mechanism was characterized using a combination of SEM, EDS and XPS. The experimental results indicated that the wear mechanisms of the cermets were mainly abrasive wear, adhesive wear, and the formation of an oxide film. As the content of Mo₂C increased from 4 wt.% to 12 wt.%, the friction coefficient and wear volume had a variation law of first decreasing and then decreasing, and reached minimum values at 6 wt.% and 12 wt.%, and the lowest friction coefficient and wear rate were 0.49 and 0.9 × 10⁻⁶ mm³/Nm, respectively. The 6 wt.% Mo₂C greatly improved the hardness and fracture toughness of the cermet, while the 12 wt.% Mo₂C promoted the formation of an oxide film and protected the friction surface. The cermet with 6 wt.% Mo₂C is recommended because it has comprehensive advantages in terms of its mechanical properties, tribological properties, and cost. Full article

Ball burnishing is a very promising alternative to grinding because of it produces little environmental pollution. It can cause improvement of the functional properties of machine parts, such as friction and wear. The connection between the ball burnishing and the lubricated fretting has not been analysed yet. In this study, it was found that ball burnishing discs from titanium alloy Ti6Al4V caused a decrease in the height of the roughness up to 84% and an increase in the microhardness up to 26% compared to the turned surface. Tribological experiments were carried out under lubricated fretting conditions. Ceramic balls from WC material co-acted with the burnished discs. Ball burnishing resulted in significant improvement in the tribological behaviour of the ball-on-disc sliding pair. Due to ball burnishing, the friction coefficient decreased up to 45% and the volumetric wear of the disc decreased up to 50% compared to the turned disc. The smallest friction and disc wear were achieved for the sample burnished with a pressure of 30 MPa; this sample was characterised by a low roughness height and great microhardness. The turned disc sample corresponded to high friction and wear. Wear losses of the balls were negligible due to the large difference between the hardness values of the balls and discs. Full article

This study aimed at the mechanical characterization, on a nanometric scale, of the constituents obtained for different fractions in duplex stainless-steel plates subjected to 850, 950, 1000, and 1150 °C heating treatments via hardness measurements and determining their influences on the fretting wear behavior of the studied steel. The obtained ferrite (α)-, austenite (γ)-, and sigma (σ)-phase fractions were determined using optical microscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD) techniques. The mechanical characterization was carried out using hardness measurement and fretting wear techniques via nanoindentation. For comparison purposes, the Vickers microhardness was also characterized to determine the effect of the σ phase, which eventually formed, on the obtained microstructure properties as a whole. Two distinct behaviors were observed, depending on the eventual formation of σ phase as a function of the treatment temperature: (i) specimens treated at 850 and 950 °C showed a hardening effect (HV_0.5 values of 333 ± 15 and 264 ± 13, respectively) due to σ-phase precipitation (hereafter termed ‘as-aged’), and (ii) specimens treated at 1000 and 1150 °C (with HV_0.5 values of 240 ± 13 and 249 ± 4, respectively) showed no σ-phase precipitation (hereafter termed ‘as-solubilized’). The increases in the microhardness values for the as-aged specimens were attributed to the hardness of the σ-phase precipitates (which showed nanohardness values varying in the 8.0–8.5 GPa range), which was approximately twice that of the austenite and ferrite grains (both phases showed nanohardness values in the 3.6–4.1 GPa range, on average). When formed (for fractions on the order of 8% and 3% at 850 and 950 °C, respectively), σ phase was mainly observed at the α/γ grain interfaces or boundaries. Fretting wear tests, using a diamond sphere with a radius of 10 μm as the counter body and a load of 20 mN, revealed the same wear mechanisms in the α/γ matrix for all studied conditions. However, as-solubilized specimens (heat-treated at 1000 and 1150 °C) displayed higher resistance to fretting micro-wear in the austenitic grains compared to the ferritic grains, indicating lower plastic deformation in the respective wear scars on the obtained tracks. In particular, as-aged specimens (heat-treated at 850 and 950 °C) exhibited lower coefficients of friction due to their higher surface resistances. The localized wear at σ-phase grains was much less pronounced than at ferrite and austenite grains. Overall, this study provides valuable insights into the mechanical behavior of microstructural changes in duplex steel at the nanometric scale. Full article

With an expectation of an increased number of revision surgeries and patients receiving orthopedic implants in the coming years, the focus of joint replacement research needs to be on improving the mechanical properties of implants. Head-stem trunnion fixation provides superior load support and implant stability. Fretting wear is formed at the trunnion because of the dynamic load activities of patients, and this eventually causes the total hip implant system to fail. To optimize the design, multiple experiments with various trunnion geometries have been performed by researchers to examine the wear rate and associated mechanical performance characteristics of the existing head-stem trunnion. The objective of this work is to quantify and evaluate the performance parameters of smooth and novel spiral head-stem trunnion types under dynamic loading situations. This study proposes a finite element method for estimating head-stem trunnion performance characteristics, namely contact pressure and sliding distance, for both trunnion types under walking and jogging dynamic loading conditions. The wear rate for both trunnion types was computed using the Archard wear model for a standard number of gait cycles. The experimental results indicated that the spiral trunnion with a uniform contact pressure distribution achieved more fixation than the smooth trunnion. However, the average contact pressure distribution was nearly the same for both trunnion types. The maximum and average sliding distances were both shorter for the spiral trunnion; hence, the summed sliding distance was approximately 10% shorter for spiral trunnions than that of the smooth trunnion over a complete gait cycle. Owing to a lower sliding ability, hip implants with spiral trunnions achieved more stability than those with smooth trunnions. The anticipated wear rate for spiral trunnions was 0.039 mm³, which was approximately 10% lower than the smooth trunnion wear rate of 0.048 mm³ per million loading cycles. The spiral trunnion achieved superior fixation stability with a shorter sliding distance and a lower wear rate than the smooth trunnion; therefore, the spiral trunnion can be recommended for future hip implant systems. Full article