Comparison of tribological properties of metal-metal and metal-cermet couples under lubricated and dry conditions

The focus of this paper is on the determination of friction, wear and film forming characteristics in conventional metal-metal couples and in cermet-metal couples. The tribological behaviour of a WC-Co based cermet applied by the HVOF process to a carbon steel substrate has been investigated in contact with cast iron, and this behaviour has been compared with carbon steel-cast iron couples. A mineral oil, a mineral oil containing zinc dialkyldithiophosphate (ZDDP), and a fully formulated lubricant were used for lubrication. The results show that the behaviour of the lubricant, in terms of its film forming and friction behaviour, is critically dependent on the load. The oil containing ZDDP shows a very significant increase in its ability to form a boundary film as the loan increases.