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

Abstract

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.