The Influence of Stress Concentration Caused by Surface Dimples on Tribochemical Reaction of Solid Lubricants Encapsulated in Surface Dimples

The combination of surface dimples and solid lubricant can improve the friction state between moving parts. However, the presence of surface dimples also leads to surface stress concentration, and the influence of these stresses on tribological properties is also worth studying. In this work, solid lubricant mixture polyimide and tungsten disulfide were firstly encapsulated in the dimples on the cylinder liner surface. The influence of surface stress concentration on the anti-friction performance of moving parts was then investigated through surface stress simulation and reciprocating friction and wear experiments. The results indicated that during reciprocating friction movement, surface stress concentration caused by the dimples mainly appeared at their edges. Moreover, as the diameter of the dimples increased, there was a gradual decrease in maximum surface stress on the cylinder liner. However, higher contact pressure and shear stress generated by edge-induced stress concentration could promote tribochemical reactions between Fe matrix and mixed solid lubricants polyimide and tungsten disulfide, resulting in formation of a solid lubrication film as well as iron–carbon and iron–nitrogen compounds that enhanced anti-friction effects.