Observation And Analysis To Boundary Layer Behavior In Mixed Lubrication Interface Of Particle Medium

Application of particles medium lubrication in hot forming is an important direction of tribology research. In light of the present study of particles lubrication, the friction and wear testing machine was used to study the process of powder particles lubrication. A variety of surface analysis technology was used to analysis the surface of the powder boundary layer, which is in the hope to reveal the lubrication mechanism.Firstly, the boundary layer behaviors of mixed lubrication interface were studied under different working conditions. The change information of coefficient of friction, temperature, three dimensional surface microstructure and surface morphology were analyzed by changing the load, speed, amount of graphite powder, the surface structure of upper specimen and the surface roughness lower specimens. There are some results. Along with the change of working condition, powder particles lubrication is acting with time-varying and in the mixed lubrication state. Appropriate increase of load and speed were favorable for the formation of the powder boundary layer. Adding more the amount of graphite powder, friction coefficient is smaller, and finally reaching a threshold friction coefficient. Increasing notches on the surface of upper specimen and roughness on the surface of lower specimen can improve the effect of lubrication.Secondly, the evolution process of boundary layer in mixed lubrication interface of particle was analyzed. Three-dimensional profilometer, laser microscopic system of shape measurement, scanning electron microscope, and laser confocal raman spectrometer are used to analysis tested surface of particular time of four typical stages, and the rule of evolutionary change can be got. The conclusion is that the evolution process of powder lubrication is divided into four stages:running-in, stable, deterioration and damage. With running of friction pair, the roughness of the surface of powder boundary layer is increasing gradually. The amount of carbon content is becoming less and less, and the amount of copper content is becoming more and more. The existing iron of tested surface was detected, and the degree of disorder of carbon increases in the failure stage. The boundary layer surface is changing from the full of the powder film to the damaged, and finally, the metal of specimen surface is exposed. The model of mixed lubrication of powder particles reveals that the presence of typical surface state is relate on the over lapping volume of dual rough peak of the friction pair surface, and is a comprehensive effect.