Role of Surface Topography on Friction and Transfer Layer Formation: A Study Using Inclined Scratch Test Available to Purchase

Tribological interaction between two contacting surfaces is influenced by many factors such as relative motion, normal load, environment, and lubrication apart from surface characteristics of the mating surfaces. Though surface characteristics such as roughness was dealt by many researchers for decades, the other important characteristic of surfaces, surface topography, has not got its share of attention. In the present investigation, basic studies were conducted using Inclined Scratch Tester to understand the role of surface topography on friction and transfer layer formation. A tribological couple made of copper pin against EN8 flat was used in the tests. Two surface parameters of steel flats — roughness and texture — were varied in tests. Care was taken to ensure that the surface roughness, measured along the scratch direction, had similar values for different textures, namely Unidirectional, 8-ground, and Random. It was observed that the transfer layer formation and the coefficient of friction along with its two components, namely adhesion and plowing, are controlled by the nature of surfaces and are independent of surface roughness. The plowing component of friction was highest for the surface that promotes plane strain conditions near the surface and was lowest for the surface that promotes plane stress conditions near the surface.