Peiyun Zhang

Tribological Properties of Laser Microtextured Surface Bonded With Composite Solid Lubricant at High Temperature

A combination technology of the solid lubricant and the laser surface texturing (LST) can significantly improve the tribological properties of friction pairs. The plate sample was textured by fiber laser and composite lubricant of polyimide (PI) and molybdenum disulfide (MoS2) powders were filled in the microdimples. Sliding friction performances of micron-sized composite lubricant and nano-sized composite lubricant were investigated by ring-plate tribometer at temperatures ranging from room temperature (RT) to 400 °C. On the one hand, the results of the micron-sized composite lubricant show that the friction coefficient of the textured surface filled with composite lubricant (TS) exhibits the lowest level and the highest stability compared to a textured surface without solid lubrication, smooth surface without lubrication, smooth surface burnished with a layer of composite solid lubricant. The better dimple density range is 35-46%. The friction coefficients of the sample surface filled with micron-composite solid lubricant with the texture density of 35% are maintained at a low level (about 0.1) at temperatures ranging from RT to 300 °C. On the other hand, the results of the nano-sized composite lubricant show that these friction properties are better than those of MoS2-PI micron-sized composite. The friction coefficients of MoS2-PI-CNTs nano-sized composite solid lubricant are lower than those of the MoS2-PI composite lubricant at temperatures ranging from RT to 400 °C. In addition, the possible mechanisms involving the synergetic effect of the surface texture and the solid lubricant are discussed in the present work.

Tribological performance and self-lubricating mechanism of the laser-textured surface filled with solid lubricant in rolling friction pair

Purpose This paper aims to find out the tribological performance and self-lubricating mechanism of the laser-textured surface filled with solid lubricant in rolling friction pair. Design/methodology/approach The textures on the surfaces of GCr15 bearing steel were produced by acousto-optic Q diode-pumped yttrium aluminum garnet laser with the technology of “single pulse one time, repeating at intervals” and filled with composite solid lubricant. The tribology tests were conducted on the MMW-1A universal friction and wear testing machine. Findings It was found that the solid-lubricated micro-textured surface can reduce the friction coefficient effectively. The MoS2/PI composite solid lubricant works better than the single MoS2 solid lubricant, and the ratio of PI/MoS2 + PI at 20 per cent is the best recipe. The friction coefficient of the sample surfaces decreases first and then increases with the increase in texture densities, and a texture density of 19.6 per cent has the best effect on friction reduction. The friction coefficient of the textured surfaces gradually decreases with the increase in both rational speed and load. For the same texture density, the friction coefficient of textured surfaces decreases slightly with the increase in diameter. Furthermore, the mechanism of “rolling-extrusion-accumulation” occurred on the textured surface can collect the solid lubricant, thereby, improve the effect of lubricating and anti-friction. Originality/value The results of the experimental studies demonstrated the application prospect of laser surfaces texturing combined with solid lubricant in rolling friction pair.

Manufacturing of micro-textures on metals by nanosecond laser micromachining

Abstract The advantages and disadvantages between ‘single pulse one time repeating at intervals’ (SPI) and ‘single pulse multiple times continuous’ laser micromachining technology on surface textures were experimentally investigated. The micromachining of 45 steel, GCr15 steel and grey cast iron materials were also studied using the interval manufacturing technology. The efficiency of the laser processing technologies and quality of the ablated micro-dimples such as the diameter and depth were systematically analysed. The experimental results showed that, the ‘single pulse one time repeating at intervals’ (SPI) micromachining technology produced high quality dimples with less heat affected zone, smooth dimples with little slags due to its ability to effectively alleviate the negative heat accumulation effect to produce quality dimples as compared to the ‘single pulse multiple times continuous’ micromachining technology process. The diameter and depth of the micro-dimples increased generally with an increase in the laser fluence for all materials. The grey cast iron has the smaller ablation threshold with the largest dimple geometry due to its high laser absorption rate and the presence of more sulfur (S) and phosphorus (P) in the chemical composition, while GCr15 steel exhibited the smaller geometry due to its hardness.