Wear最新文献

Face-centered-cubic (FCC) compositionally complex alloys (CCAs) are recognized for their exceptional mechanical properties, rendering them promising candidates for demanding engineering applications. However, a significant challenge faced by these alloys is their limited wear resistance. In this study, we addressed this issue by introducing 5 at.% Nb into an equiatomic FCC CrFeNi alloy, thereby creating a Laves phase-strengthened CrFeNiNb_0.158 alloy, and investigated its sliding wear behavior at both room and elevated temperatures. Our findings reveal a substantial improvement in the wear performance of the Laves phase-strengthened CrFeNiNb_0.158 alloy. Specifically, at room temperature (RT), the alloy exhibited a remarkable 62 % reduction in wear rate compared to the CrFeNi alloy. Furthermore, at an elevated temperature of 600 °C, the wear rate decreased by approximately 95 %, primarily attributed to the formation of a lubricating (Cr, Fe)₂O₃ oxide layer. Through detailed analysis, we identified the wear modes as abrasive wear at RT and oxidative wear at elevated temperatures. These results provide valuable insights for designing wear-resistant FCC CCAs by utilizing Laves phase strengthening and incorporating elements prone to oxidation to facilitate the formation of a protective oxide layer at elevated temperatures.

Tempering treatment can improve the fatigue resistance while maintaining the wear resistance of laminar plasma discrete quenching (LPDQ) rails, but the fatigue crack initiation and propagation forms of LPDQ rails and tempered rails (TLPDQ) are not clear. In this study, twin-disc tests are performed on LPDQ and TLPDQ rails to obtain the wear and fatigue damage evolution of wheels and rails, and discuss the crack propagation mechanism. The results show that fatigue cracks in LPDQ rails initiate at the quenching zone edge and tend to propagate along the boundary after expanding to the quenching zone/substrate boundary in the depth direction. Whereas TLPDQ rail cracks tend to penetrate the boundary and propagate towards the substrate interior after expanding to the boundary.

In this study, the tribological behaviour of different Diamond-like-Carbon (DLC) coatings sliding against titanium alloy (Ti6Al4V) was analysed in a pin-on-disc tribometer at different applied loads to study effectiveness of tool coatings in titanium alloys machining. Three different DLC coatings were deposited on cemented carbide substrate using HiPIMS (DLC-Ar, DLC-Ne) and arc (DLC-Bn) deposition techniques. A detailed analysis of the wear track and titanium countersurfaces were performed following the tribotest to develop understanding about the wear mechanism and associated variation in the friction response. The results indicated that DLC-Ar presents low friction and reduced wear of coating and respective titanium countersurface at lowest load, seemingly due to its inherent tendency to spontaneously form graphitic transfer-layer at the interface. With an increase in the applied load, the tendency to retain tribofilm decreases as shearing ensue quickly exposing the underneath substrate material. The wear performance of DLC-Ne coatings is better than DLC-Ar under highest load and friction behaviour relatively close to DLC-Ar coatings. In comparison, under increased applied loads, DLC-Bn coatings offered better wear resistance and low friction compared with DLC-Ne and DLC-Ar coatings, which would offer improved performance in machining of titanium alloys.

Cubic boron nitride (CBN), with a hardness second only to diamond and an excellent chemical stability, is used to replace the role of diamond and machine precision/ultra-precision components in ferrous materials. However, the wear mechanisms of CBN tools and their wear-induced effects on machining system vibration seriously affect the machined surface quality. Therefore, this research focus on the wear characteristics of CBN tools in machining of NAK80. Based on the wear characteristics, the change in surface morphology and finish of the machined surface with tool wear was investigated. Meanwhile, the transformation of chip morphology at different wear stages was observed. Also, the effect of tool wear on the machining system vibration is analyzed by Butterworth filtering and Fourier transforming the cutting force signal. Research results show that the wear mechanisms of CBN cutting NAK80 are abrasive wear, oxidative wear and diffusive wear. Further, when the width of the flank wear of the CBN tool reaches 53 μm it causes multimodal vibration of the machining system, resulting in chattering patterns on the machined surface. As the width of the flank wear increased from 56.64 μm to 70.80 μm, the vibration frequency increased by 13.3 %. However, by reducing the feed rate from 5 μm/rev to 2 μm/rev, the vibration frequency can be reduced by 66.8 %. This study provides theoretical help in the research of wear of CBN cutting NAK80.

This work investigates the possibility of doping Si and Sn solid solution components (separate/simultaneous incorporation) into Ti₃AlC₂ to provide desired mechanical properties and tribological self-adaptability over a broad temperature range. The specimens are sintered at 1450 °C for 2 h in a vacuum environment with a pressure of 30 MPa. The phase composition, mechanical properties and tribological characteristics sliding against Al₂O₃ counter balls over a wide temperature range from room temperature to 800 °C are investigated. The results demonstrate considerable lattice distortion together with significant solid solution strengthening effects in quinary solid solutions. The friction coefficients of the four solid solutions are discovered to be temperature-sensitive from the distinguished variation tendencies in the wide temperature range. The wear rates exhibit a comparable tendency with test temperature that the values are two orders of magnitude lower at 600−800 °C than those at RT−400 °C. The noticeably lubricant tribofilm is responsible for the decreased wear rate at elevated temperatures. The distinct tribological behaviors of the quaternary and quinary solid solutions are ascribed to the characteristics of the self-generated oxides.

A combination of optical imaging (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atom probe tomography (APT) was used to examine the white etching layer (WEL) and brown etching layer (BEL) formed in the flow lip region of a heavy haul curved rail. These flow lips eventually serve as crack initiating regions, leading to reverse detail fractures. OM distinctly identified the WEL/BEL region based on light contrast, while SEM micrographs identified a fine-grained structure within the WEL with intermittent patches of a deformed pearlitic structure. SEM images of the WEL/BEL indicate that the fraction of cementite patches was higher in the BEL region than in the WEL. TEM investigations revealed the presence of martensite/nano-crystalline ferrite along with newly formed austenite and cementite particles in the WEL and the BEL. The ferrite/martensite grain size was much finer in the WEL than in the BEL. The lath morphology of martensite was observed in the BEL, whereas a mixed morphology of lath and twinned martensite was observed in the WEL. APT studies show no Mn/Si partitioning in WEL/BEL along with C-concentrations ranging from 10 to 15 at.% and up to 20 at.% in the WEL and BEL respectively. The synergistic effect of elevated wheel-rail contact temperatures and severe plastic deformation dictated the overall microstructural evolution of the BELs and WELs on the outer rail surface in the flow lip.

Fe–Co–Ni face-centered cubic (FCC) alloy has been one of the most extensively investigated alloys due to its potential ductility and toughness, while its low yield strength and wear resistance limit the engineering application. In this study, the different Mo content is added in the Fe–Co–Ni based alloy to solve this problem. The microstructure, wear resistance and tribological mechanism of Fe_60-xCo₂₀Mo_xNi₂₀ (x = 10, 15, 20) high-entropy alloys after different annealing treatments are systematically investigated. The results reveal that the content of the μ phase increases with the addition of Mo element when annealed at 600 °C, and the highest amount of the μ phase is observed in the Mo20 alloy. The formation of the μ phase enhances the hardness of the Mo20 alloy, reduces the surface roughness during the wear process compared to Mo10 and Mo15 alloys, thereby improving the wear resistance. Furthermore, increasing annealing temperature also affects the content and distribution of the μ phase. The Mo20 alloy annealed at 600 °C exhibits the best wear resistance. However, as the annealing temperature increases to 1000 °C, the wear resistance deteriorates due to the spalling of the μ phase. In contrast, the wear resistance of the Mo15 alloy is optimized due to the uniform distribution of the μ phase. Additionally, when the sliding force increases from 2 N to 10 N, the wear resistance of the Mo20 alloy initially deteriorates before improves. This is mainly due to the increase in abrasive wear when the load is increased from 2 N to 5 N, while as the sliding force further increases to 10 N, a glaze layer is formed on the wear surface, which produces a lubricating effect. Furthermore, the better wear resistance of Mo20 and Mo15 alloys compared with others can also be attributed to the friction subsurface with nano-scale structure.

C/SiC composites have excellent mechanical properties such as high specific strength and high temperature resistance, and are widely used in aerospace fields. However, due to its special structure and material properties, the tool wear is severe when machining with conventional methods, and the processing quality is poor. The purpose of this paper is to reveal the progressive wear behavior, wear mechanism of the tool, and its effect on machining performance in conventional milling (CM) and ultrasonic vibration-assisted milling (UVM) of C/SiC composites under forward fiber cutting (FC) and reverse fiber cutting (RC). The material removal and heat transfer models were established, and the stress distribution characteristics of cutting -edge were analyzed by finite element method (FEM). Combined with the wear morphology, cutting heat, and cutting force, the tool wear behavior and mechanism in UVM and CM under FC and RC were studied, and their effects on machining quality were analyzed. The results show that there are great differences in heat transfer and removal process between FC and RC. In UVM, the introduction of ultrasonic vibration reduces the adhesion of fine chips, weakens the strong friction and scratching between the hard chips and the cutting -edge, and alleviates the tool wear. The flank wear VB and cutting -edge wear area WA in RC are larger than those in FC, the abrasive wear is intensified, the material even peeling under mechanical shock, and the adhesive wear is more serious. When the tool wear intensifies to a certain extent, the difference of the cutting process caused by mechanical anisotropy of C/SiC composites is weakened, and the surface micro-defects and surface roughness Sa change little under FC and RC. This research contributes to the realization of high-quality and low-cost processing of C/SiC composites.

Additive manufacturing of self-lubricating alloys plays a crucial role in the production of complex wear-resistant components and in expanding repair capabilities, especially for intricate wear parts with low tolerances (e.g. with cooling channels). Herein, we report a novel approach providing nickel-based alloy with an excellent tribological performance in dry sliding contacts. Laser-deposited self-lubricating nickel alloys, infused with anti-wear additives of molybdenum disulfide, nickel sulfide, copper sulfide, or bismuth sulfide, were subjected to dry sliding wear tests against an alumina ball counterbody at a temperature range of up to 800 °C. The self-lubricating alloys exhibited a significant decline in friction (43 %) and wear (45 %) at room temperature, 400 °C (friction 40 %, wear rate 55 %), and 600 °C (MoS₂-based, friction 58 %, wear rate 75 %). The MoS₂-based alloy coating demonstrated excellent performance characteristics up to 800 °C (friction coefficient ⁓0.25, wear rate 11 × 10⁻⁶ mm³ N⁻¹ m⁻¹) due to the formation of a ‘glazed’ tribolayer. Wear mapping allowed to identification of a critical condition for self-lubricating alloys where positive transitions in wear mechanisms led to a synergistic lubrication mode involving the formation of tribologically induced new lubricious phases such as silver molybdate or nickel-bismuth intermetallic. This work provides a comparative evaluation of the micromechanisms, surface transitions, and tribochemistry of solid lubricants at a wide temperature range and a variety of applications.

A Ni–Cr–MoS₂ coating with trivalent Cr was prepared on the surface of the cylinder liner by the composite co-deposition method to modify its tribology performance. The effects of MoS₂ concentration on the properties of the coatings and tribological properties of cylinder liners were studied by surface detection methods and reciprocating wear tests. The results show that Ni–Cr–MoS₂ coating has a smaller grain size, higher micro-hardness, and greater coating thickness, compared with Ni–Cr coating. Doping by MoS₂ effectively reduces the friction coefficient of Ni–Cr coating from 0.142 to 0.107, the wear amount of coating decreases from 7.9 mg to 7.1 mg, and the scuffing time increases from 19 min to 56 min. It is found that the doping of MoS₂ provided more nucleation sites and promoted the deposition of ions, which resulted in the refined grain and thicker coating. The formation of solid lubrication film by MoS₂ during the wear process and more coating thickness are mainly responsible for the modification of the tribology performance of cylinder liners. This research provides a practical approach to prolong the service life of friction pairs.