Effects of Extreme Pressure Additives on Friction and Wear Properties of Ceramic Coatinqs

The effects of several extreme pressure (EP) additives on friction and wear properties of ceramic coatings was studied using a block-on-ring test machine at ambient condition. The results shown that the wear property of ceramic coating depends strongly on the combination of tribo-couples and types of EP additives, while the friction properly is insensitive to these factors. Of EP additives used in this experimenty Zinc dialkyldithiophosphate (ZDDP) and tricresyl phosphate (TCP) have significant wear-reducing function for various tribo- couples, whereas the P-N agent is not good at antiwear effect even it has the wear-increasing effect. It is also found through EPMA and XPS analyses of worn surfaces of TiO2 coatings that adsorbed layers of lubricating oils and additives were formed on wear tracks and outside during rubbing process, wear-resistance of ZDDP and TCP is due to the physical adsorption of them on ceramic coating surfaces.