Effect of annealing treatment on the tribological performance of hydrogenated amorphous diamond coatings doped with nitrogen

Abstract

Pure a-C:H and some nitrogenated coatings (a-C:N:H) with 0.12–2.95 at%N were deposited onto 316 L and Si wafer via the plasma-enhanced chemical deposition (PECVD) technology. Pin-on-ball sliding tests against Al2O3 balls were carried out for as-deposited and annealed coated specimens. The micro-morphology and chemical bonding structure of these coatings with different treatments were characterized using FE-SEM, FTIR, Raman, and XPS. The OH group can be incorporated into the coating bulk, and becomes the active site that reacts with the dangling Al on the counter-body surface to increase the coefficient of friction (CoF), thus gradually increasing the abnormal transition stage occurring in the CoF-sliding time curve. N doping transforms the OH group into NO and CO bonds, and enhances the O/C ratio in the coating to increase the wear rate. Either as as-deposited or an-annealed, the CoF of the pure a-C:H coating always raised with sliding distance, and it was larger than the N-doped coatings. However, the N doped coatings presented higher wear rate. The a-C:N:H coating with 0.12 at% N exhibited the best anti-wear performance, which was with almost the same wear rate as a pure a-C:H coating.