Study of a-C:H thin films deposited by Plasma Immersion Ion Implantation for mechanical and tribological applications

The tribological and mechanical properties of DLC films deposited on the surface of 16MnCr5 steel alloy were investigated. The major concerning of using DLC layers on engine parts are: (i) to reduce friction; (ii) to increase fuel efficiency and to reduce CO2 emission; (iii) to increase hardness of alloy steel. After polished and ultrasonicated, 16MnCr5 substrates were submitted to PIIID procedures in radiofrequency plasmas (13.56 MHz) generated from atmospheres of methane and argon. Excitation power and total gas pressure were kept constant. It was investigated the effect of methane proportion on the microstructure and mechanical properties of the films using the follow techniques: Raman Spectroscopy (for Hydrogen content and microstructure analysis), Ultra Micro-Tribometer (for friction coefficient) and Nanoindentation (hardness evaluation). Raman analysis confirmed DLC character of the films produced, and the proportion of 80% methane and 20% argon resulted to the best performance of mechanical properties of the films owing to the increase of hardness in until ten times, and reducing the friction coefficient to about 0.2. In addition, thickness for these films varied from 165 nm to 206 nm.