Purpose The purpose of this paper is to describe the tribological characteristics with different area density of concave-convex micro-texture on the mold surface. It is a new technology to improve the quality of the workpiece to control the tribological properties through the application of concave-convex micro-texture on the mold surface. Design/methodology/approach Five groups of laser micro-texture with different area density (ratio of the concave-convex micro-texture area to the all-area) were processed on the surface of the mold steel, and the tribological properties were compared with the smooth surface of the reference sample. Findings The time of the running-in stage in different experimental groups was about 300 s. The fluctuation amplitude of concave-convex micro-texture friction coefficient is much larger than that of smooth plane specimen in the running-in stage. After the running-in stage, the friction coefficients were lower than that in the smooth condition and decreased with the increase of the concave-convex micro-texture area density. When the area density reached 25%, the friction coefficients no longer decreased significantly. In addition, the wear of concave-convex micro-texture surface is much lower than that of smooth surface and decreases with the increase of concave-convex micro-texture area density. Originality/value Domestic and foreign scholars have done a lot of research on the relationship between concave micro-texture and tribological properties. However, the object of this paper is a new concave-convex micro-texture, which is rarely studied in the field of tribology. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-03-2020-0081/

A two-dimensional analytical model based on the Reynolds equation considering mass conservation cavitation is proposed to investigate the performance of partially textured thrust bearings with circular grooves. The geometrical and distribution parameters of the circular grooves are numerically optimized to obtain the maximum load-carrying capacity. The samples of partially textured thrust bearings are machined by the picosecond laser, and tribological experiments are carried out on an MMW-1 tribological rig. The average friction coefficient and the friction reduction ratio are applied to analyze the tribological performance of partially textured thrust bearings. Through a comparative analysis, the optimal geometrical values obtained from the experimental results are in good agreement with the theoretical analysis, especially at high rotation speeds and a low load condition.

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This paper is to evaluate and compare the tribological properties of lubricating oil blends added with nano graphene and lubricating oil blends added with cerium oxide (CeO2) on the key friction pairs of the diesel engines. The dispersion stability is the premise of studying the tribological properties. In this paper, nano-CeO2 particles were self-made and high-quality nano-graphene was purchased. The dispersion stability of the two nanomaterials in lubricating oil was studied after the same modification respectively. According to the working conditions of the cylinder liner and the piston ring, the friction and wear tests of the lubricating oil blends added with the modified nanomaterials were carried out at the different temperatures. The results showed that the oleic acid and the stearic acid modified the two nanomaterials successfully. The dispersion stability of the modified nanomaterials in lubricating oil was improved. The dispersion stability of the lubricating oil blends added with graphene before and after modification was slightly higher than that of lubricating oil blends added with CeO2 before and after modification, respectively. At the high temperature, the anti-friction property of the two nano lubricating oil blends was similar. At the ambient temperature, lubricating oil blends added with modified CeO2 did not play a role in reducing friction, while lubricating oil blends added with modified graphene had the effect of reducing friction. Whether at ambient temperature or at the high temperature, the anti-wear property lubricated with lubricating oil blends added with modified CeO2 within the right concentration range was better than that lubricated with lubricating oil blends added with modified graphene.

Good dispersion stability of lubricating oil blends added with graphene is the premise of playing its superior tribology property. In this paper, the dispersion stability of modified graphene in lubricating oil and the wear property of nanolubricating oil on the key friction pair for a diesel engine was studied by simulation and experiment. The results showed that the dispersion of modified graphene in lubricating oil was improved at ambient temperature and pressure and at high temperature and pressure. However, the dispersion effect of graphene at high temperature was slightly worse than that at ambient temperature. The wear property of lubricating oil blends added with modified graphene with a concentration of no more than 100 ppm was improved. With the increase of graphene addition, the wear reduction effect increased first and then decreased. The lubricating oil blend added with 25 ppm modified graphene is the best for wear reduction.