Modelling of tribo-chemical reactions in HiPIMS W-C:H coatings during friction in different environments

Abstract

The modelling of simultaneous chemical reactions in complex systems was successfully applied to mechano(tribo)chemical reactions during friction between steel ball and High Power Impulse Magnetron Sputtered (HiPIMS) W-C:H coatings in humid air, dry nitrogen, hydrogen and in vacuum. The main mechano(tribo)chemical reactions leading to transfer layer formation in humid air - oxidation of WC and Fe, water vapor decomposition and carbon hydrogenation - were confirmed. In nitrogen, the decomposition of WC producing carbon was predicted. The prediction in hydrogen was only the formation of methane. In vacuum, the decomposition of WC and FeOWO3 into W and Fe and CO formation were dominant. Thus, the friction is controlled via amount of hydrogenated carbon resulting from the dominant mechano(tribo)chemical reactions.