Relationship between oxidation behavior and tribological properties of Mo-V-Cu-N coatings

In this study, the relationship between tribological properties and oxidation behavior of Mo-V-Cu-N coatings was explored. Due to tribo-oxidation at RT, some rod-shaped lubricious oxides (e.g., MoO3, CuMoO4, V2O5) formed on worn surfaces, contributing to an excellent wear performance, including a low friction coefficient of 0.3 and wear rate of-10-17 m3/N center dot m. However, due to the abrasive wear under dry friction at 300 degrees C, the friction coefficient sharply increased to 0.57-0.67. The coatings started to be oxidized at 400 degrees C, and showed obvious oxidation delamination at 3.6 at.% V. Many bulk-like (CuMoO4) and plate-like (MoO3) oxides formed on the top layer by outward diffusion and oxidation, resulting in a low friction coefficient of 0.45 at 400 degrees C. Due to serious oxidation at 500 degrees C, double-layer oxides formed, and the wear rate sharply increased to-10-14 m3/N center dot m. With increasing V content, the fraction of CuMoO4 and MoO3 lubricious oxides decreased, resulting in an in-crease in the friction coefficient, whereas the wear resistance was enhanced, especially at high temperatures.