Effect of powder lubrication on wear characteristics of silicon nitride during sliding at high temperature

In order to improve the tribological characteristics of Si3N4 friction pairs at high temperature, graphite powder, h-BN powder and MoS2 powder with excellent lubricating properties were added between the friction pairs. The friction and wear experiments of different powder adding stages (initial adding stage and stable friction stage) and different temperature gradients (25 degrees C, 100 degrees C, 200 degrees C, 300 degrees C, 400 degrees C) were carried out on the friction and wear tester. After the experiment, the worn surface was observed by SEM and ultra-depth microscope, and the lubricating powder before and after friction was analyzed by XRD. Combined with the friction coefficient recorded during the experiment, the friction reduction mechanism of powder lubrication under different conditions was analyzed and summarized. The results show that the three kinds of powder all have the best lubrication effect at the initial stage of addition. With the increase of temperature, the film-forming ability of graphite powder and h-BN powder decreases, and MoS2 powder is little affected. Therefore, the key to lubrication and wear reduction is to form a dense, stable and not easily damaged lubricating film during friction. How to form the lubricating film more easily and how to improve the performance of the lubricating film will become the next research focus.