Current Issue : October-December Volume : 2026 Issue Number : 4 Articles : 5 Articles
This study focuses on China’s domestically developed K452 alloy. Using Si3N4 ceramic balls as the counterface material, the tribological properties of the K452 alloy were investigated after heat treatment over a wide temperature range (RT–800 ◦C), and the wear mechanisms were analyzed. The results show that the heat treatment process enhances the material hardness slightly by promoting the dissolution of the γ′-strengthening phase and the precipitation of the η phase. From RT to 600 ◦C, the wear rate of the K452 alloy remains at a relatively low level, on the order of 10−6 mm3·m−1·N−1. Compared with the as-cast condition, intermediate treatment exhibits a significant reduction in the wear rate. Compared with traditional processes, it reduces one step of heat treatment. This improvement is attributed to the precipitation of the uniformly fine η phase, along with the re-dissolution of the γ′-strengthening phase. When the testing temperature is raised to 800 ◦C, the tribological performance of the K452 alloy deteriorates significantly, with the wear rate increasing to the order of 10−5 mm3·m−1·N−1. Microstructural characterization confirms that the in situ formations of dense Cr2O3 and Al2O3 oxide films during friction are the primary mechanism for improved wear resistance from RT to 600 ◦C. But when the temperature rises to 800 ◦C, the dynamic equilibrium of the oxide layers is disrupted, leading to oxidative wear becoming the dominant mechanism....
This article demonstrates that ion implantation is an effective surface-modification method for tailoring the tribological performance of hydrogenated amorphous carbon (a-C:H) thin films. Nanometerthick a-C:H films were implanted with various ion species (Si, Ti, Hf, and W) at low and high doses and species-specific energies, and their sliding behavior against Al₂O₃-TiC counterfaces was systematically investigated. The results reveal that implantation conditions strongly affect atomic mixing, defect generation, and local structural rearrangements in the carbon matrix. Si implantation produced only marginal improvements in wear resistance, with abrasive wear remaining the dominant mechanism. In contrast, Ti, Hf, and W implantation led to substantial enhancements in tribological performance, with high-dose Ti implantation yielding the most pronounced benefits. Implantation induced a transition in the dominant wear mechanisms from micropitting and debris plowing to nano-asperity removal, attributed to an ion-modified intermixing layer, which suppresses plastic shearing and increases the wear resistance of the a-C:H films....
While sliding friction at the nanoscale is routinely measured by colloidal probe lateral force microscopy (CP-LFM), measuring rolling friction at this scale remains challenging due to the difficulty of resolving lateral forces and particle rotation under well-defined normal loads. Here, we present an extension of a recently published platform that uses free-colloidal probes to enable quantitative measurements of both sliding and rolling friction at individual particle–substrate contacts. Our approach combines a custom-made colloidal probe with a holder for free particle rotation with lateral force detection and optical particle tracking. The modular holder design is compatible with particles of different sizes and materials, enabling studies of many systems of interest. We functionalize the holder surface using a lubricious poly(ethylene-glycol) (PEG) brush to minimize the internal friction of the free-moving particle within and extend the regime in which rolling friction can be measured. In addition, we present a scalable synthesis route for smooth, polymeric particles with tunable size (3–8 μm) and anisotropic fluorescence, enabling direct tracking of particle rotation without modifying native surface properties. Together, these developments establish free-colloidal probe LFM, or fCP-LFM, as a robust and adaptable tribological platform for quantifying friction at the microscale under different modes of relative motion, suitable for systematic studies of nanoscale particle–surface interactions across a wide range of materials and conditions....
This study investigates spherical methyl silicone resin, a potentially environmentally friendly additive free of sulfur, phosphorus, and chlorine, as a lubricant additive in polyethylene glycol 200 (PEG 200) base oils. We evaluated concentration-response characteristics and tribological performance across PEG base oils containing 0.01–0.05 wt% resin. Tribological testing was conducted with a four-ball wear tester at 98 N and 1450 rpm for 30 min. All tested concentrations demonstrated excellent friction-reduction and anti-wear performance, with an optimal efficacy observed at 0.02 wt%. Surface characterization was performed using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. This friction- reducing and anti-wear performance is attributed to the formation of silicon-oxygen species and graphene-like carbon structures, thereby effectively suppressing direct surface contact and mitigating wear. Consequently, spherical methyl silicone resin demonstrates considerable potential as a green lubricant additive for bearing steel applications....
Coatings based on aluminum and titanium nitrides are widely used in industrial applications due to their versatility and properties (wear resistance, hardness, and oxidation resistance). The addition of elements such as boron can improve the tribological properties. However, the influence of surface finish can strongly influence the performance of the coating. In this study, flat samples with different surface finish and real forming tool components are coated with AlTiBN via PVD. The structure and chemical composition of the coatings are studied using scanning electron microscopy (SEM) and GD-OES. Rockwell tests are used to evaluate the adhesion to the substrate, and nanoindentation is used to characterize the mechanical properties of the coatings. Pin-on-disc tests are carried out to study wear resistance of coated samples. Coated forming tools are used in-service applications to test the performance of the coating and corroborate the results. The lifetime of components for forming applications increases. The influence of underlaying substrate’s roughness is mitigated by the AlTiBN upper coating, thus obtaining similar results to middle polished and high-quality polished substrates in terms of wear resistance. However, poor polishing and too rough surfaces show direct influence on the wear behavior of the components, presenting higher wear rate values....
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