Tribological evaluation of hydrogenated DLC in Diesel lubricated model test

Abstract

In this paper, the wear behaviour of hydrogenated diamond like-carbon (DLC) in DLC/steel tribological contact in the skewed cylinders model test under Diesel lubrication was investigated. Standard Diesel EN590 (according to the European norm) was used as a lubricant. The considered DLC was the hydrogenated amorphous (a-C:H, called DLC), deposited on 100Cr6 steel substrates. The effects of load, contact duration, temperature and speed on DLC and steel tribological behaviours in the skewed cylinders model test were investigated. It was experimentally seen that the DLC wear rate increases with increasing sliding distance, contact pressure and temperature. The wear rate of the 100Cr6 counterbody was observed to be independent of the test conditions. Furthermore, the DLC wear rate was found to be higher than that of the 100Cr6 steel counterbody, especially at a high temperature and/or load. This observation is valid only in the case of DLC/100Cr6 tribological contact. The DLC wear was observed to be driven by the graphitisation of the outermost layer, whereas the wear behaviour of the counterbody was dominated by the formation of a tribological induced layer. Based on the mechanism responsible for the DLC wear, a physical motivated new wear law was developed and proposed. This law allows to predict the wear volume as a function of pressure, temperature and contact duration.