Effect of Water on Wear of DLC Coatings in high temperature and pressurized Ethanol

Abstract

This study investigates the impact of moisture and dissolved oxygen on the wear behavior of a-C:H:Si coatings in high-temperature high-pressure ethanol-water conditions. Friction and wear tests were conducted on hydrogenated amorphous carbon (a-C:H) and silicon-containing a-C:H:Si coatings under varying moisture levels (0 vol.%, 6 vol.%) and dissolved oxygen conditions (N2, O2 10 MPa) at 120°C. The results revealed distinct wear responses between a-C:H and a-C:H:Si coatings. Under O2 pressure, a-C:H coatings showed minimal change in wear with increasing moisture levels, while a-C:H:Si coatings exhibited a notable doubling in wear, indicating higher susceptibility to moisture. Auger electron spectroscopy analysis confirmed that a-C:H:Si coatings underwent surface oxidation with increased moisture, leading to significant changes in elemental composition. Additionally, atomic force microscopy scratch tests revealed surface softening in a-C:H:Si coatings, particularly under moisture conditions. The study suggests that moisture induces surface reactions in a-C:H:Si coatings, resulting in increased wear, providing insights into the wear mechanisms influenced by moisture and dissolved oxygen in ethanol-water environments.