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A Ni–Cr–MoS 2 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 MoS 2 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–MoS 2 coating has a smaller grain size, higher micro-hardness, and greater coating thickness, compared with Ni–Cr coating. Doping by MoS 2 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 MoS 2 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 MoS 2 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. • The inclusion of MoS 2 significantly increased the Ni–Cr coating thickness. • The doping of MoS 2 increased nucleation sites and changed the coating structure. • The friction and scuffing properties of cylinder liner were significantly improved. • A solid lubrication film produced on the surface of composite coating by MoS 2. [ABSTRACT FROM AUTHOR]

The textured surface is one of the hotspots in the field of tribology research on reducing friction and wear. By calculating and optimizing the micro-texture structure, researchers designed and prepared textures with excellent tribological properties on the mechanical part surfaces. In this work, the tribological performance of 42CrMo matrix composite textured surfaces (CTSs) with different textured densities under grease lubrication was studied. The CTS was composed of 42CrMo alloys and SnAgCu-MXenes-Ti 3 C 2 (SACM). The results showed that when the textured density ρ of CTS was 36%, the friction coefficient (0.090) and wear rate (5.4 × 10−9 mm3N−1m−1) of counterpart ball could be respectively reduced by 75.7% and 38.6% compared with those of counterpart ball against the untextured sample. CTS could enhance the stability of friction system. Mxenes-Ti 3 C 2 wrapped by SnAgCu could form the lubricating layer containing sub-micron rollers on the worn surface, effectively reducing the friction and wear of samples under grease conditions. [Display omitted] • The composite textured surfaces (CTSs) were designed and prepared. • MXenes wrapped by SnAgCu could form sub-micrometer rollers in wear scar. • CTS exerted tribological enhancement function under starvation. • CTS could produce excellent synergistic effect with grease. [ABSTRACT FROM AUTHOR]

The combination of texturing pretreatments and lubricant films was researched to improve the dry friction and wear performance of aluminium alloys. Three linear microtextures with different spacings were fabricated on the aluminum alloy substrates by ultrasonic surface rolling processing (USRP). The surface characteristics of different microtextures, such as micromorphologies, hardnesses, and wettability, were tested. PTFE/PPS lubricant films were prepared onto the textured surfaces by electrohydrodynamic atomization (EHDA), and micromorphologies of the films were observed. The friction and wear performance of aluminum alloy substrate and the films with texturing pretreatments were tested by ball-on disk reciprocating sliding dry friction experiments, and the countball material was 316L steel. The test data indicated that all films effectively reduced the friction coefficient of the substrate surface, and among them, the film sample URTC100 with a combination of 100 μm spacing texture and PTFE/PPS film exhibited the best effect of anti-wear while dry reciprocating sliding. Compared to the unpretreated film sample, URTC100 increased the wear life by 10% and reduced the wear track width and adhesion width by 35% and 25%, respectively. • Ultrasonic surface rolling processing was used to prepare surface textures. • Electrohydraulic atomization was used to fabricate PTFE/PPS lubricant films. • The above two methods were synergistic on dry tribological property improvement. [ABSTRACT FROM AUTHOR]

Abstract: The tribological properties of rhenium-doped inorganic fullerene-like MoS2 nanoparticles were studied in poly alpha olefin oil, and compared to inorganic fullerene-like (IF) MS2 (M=Mo,W) nanoparticles and 2H-MoS2 platelets. For this purpose a rotational disc tribometer was used. Different regimes in the Stribeck curve, i.e., boundary, mixed and elasto-hydrodynamic lubrication conditions were studied. A precipitous reduction in friction and wear of oil suspensions with nanoparticles were observed for the entire IF samples. However, Re-doped IF exhibited the best results, presumably due to their reduced tribocharging and agglomeration. The various tribological mechanisms of solid state additives are discussed. [Copyright &y& Elsevier]

Tribo-machineries employ machine elements, such as discs and gears, which are frequently subjected to Hertzian loads that cause their mechanical failure. Case hardening is a popular method that ensures better productivity and performance of such elements compared to its untreated variants. This paper presents a wear and fatigue model for case hardened steels under Hertzian loads in line contact. Steel discs with different case hardening depths were tested using a three-disc testing machine, and the samples were analyzed using optical microscopy, SEM and a portable X-ray diffractometer. The influence of type of contact, case hardening depths, normal force (contact stress) and slip conditions on the damage process are investigated in detail. It was found that the hardening layer should be adapted to the load, since a too large hardening depth means a shorter service life due to higher residual stresses gradients. The transferability of results to increase the service life of real-life components is an essential component of this work. • Wear & fatigue model for case hardened steels under Hertzian loads in line contact. • Steel with different case depths tested using a three-disc machine. • Influence of contact, normal force and slip conditions on the damage investigated. • It was found that the hardening layer should be adapted to the load. • The transferability of results to real-life components is highlighted. [ABSTRACT FROM AUTHOR]

This paper describes the evolution of friction-induced microstructures underneath the wear surfaces of nickel single crystals, and their role in influencing the steady state coefficient of friction. Using a custom built tribometer, friction measurements were made on {001} and {011} crystal faces along several crystallographic directions in unidirectional linear mode with a Si 3 N 4 ball. Cross-sections of wear scars were prepared by focused ion beam (FIB) microscopy, and electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM) were used to analyze the evolution of crystallographic texture and recrystallization. The formation of a thin (10–15 nm) ultra-nanocrystalline layer in the {011}<211> orientation resulted in significant reductions in the coefficient of friction for that configuration, from the initial maximum of 0.64 to a steady state value of 0.32, after approximately 500 cycles of linear, unidirectional sliding. Crystal plasticity theory was used to describe the evolution of dislocation content in the worn material, which in turn provides an estimate of the characteristic grain size as a function of the imposed strain. An analysis of grain boundary sliding in ultra-fine-grained material suggests a mechanism for friction reduction. Model predictions of the contribution of grain boundary sliding (relative to plastic deformation) to friction provide a phenomenological description of the lubrication due to ultra-nanocrystalline surface microstructures. • A novel combination of electron microscopy and tribotesting techniques were utilized. • Friction measurements on single crystal surfaces along specific crystallographic directions was demonstrated. • Subsurface characterization provided insights into the relationships between microstructure and friction. • A model was proposed to help understand the relationships between plasicity, microstructure, and friction. • The model predictions agree well with the available observations and measurements. [ABSTRACT FROM AUTHOR]