Influence of production process-induced surface topologies at varying roughness depths on the tribological properties of polyamide steel contact

Friction and wear in a tribological system are directly dependent on the surface structure and roughness of the friction partners involved. In this article, a clear interaction between surface topologies and their roughness depth was identified for the material pairing polyamide 66 - steel. The typical correlation between roughness and wear, initially decreasing and increasing after a wear minimizing roughness, was found for all surface topologies, albeit at different levels. The effect of the surface topology is negligible at low roughness (S-z < 2.0 mu m) with adhesive wear processes determining the wear behaviour. At higher roughness depths (S-z > 2.0 mu m), the ability of the surface topology to form a stable transfer film determines the tribological behaviour by limiting the effect of abrasive wear processes. A stable transfer film is formed with sufficient roughness and undercuts in the direction of motion, which can be characterised by the average roughness depth, R-z , in the direction of motion. Based on these empirical results, an explanatory model for the observed behaviour is presented.