Role of surface texture and roughness parameters in friction and transfer layer formation under dry and lubricated sliding conditions

Surface texture influences friction and transfer layer formation during sliding. In the present paper three well-defined surface textures, namely unidirectional, 8-ground, and random, were employed on steel plates. Experiments were conducted on a tribological couple - zinc pin against steel plate - using an inclined pin-on-plate sliding tester. It was observed that the occurrence of stick-slip motion, the transfer layer formation and the value of coefficient of friction as well as its two components, namely adhesion and plowing, depend primarily on surface texture. The effect of surface texture on coefficient of friction was attributed to the variation of the plowing component of friction for different surfaces. The plowing component of friction was highest for the surface texture that promotes plane strain conditions while it was lowest for the texture that favors plane stress conditions at the interface. Dimensionless quantifiable roughness parameters were formulated to describe the degree of plowing and hence the plane strain/stress type deformations taking place at the asperity level.