High Temperature Tribological Properties of Al2O3/NCD Films Investigated Under Ambient Air Conditions

Comparative analysis of dry sliding wear behavior of nanocrystalline diamond (NCD) films and NCD films coated with a thin Al2O3 layer (Al2O3/NCD) is the main goal of the present study. Plasma-enhanced chemical vapor deposition (PECVD) and atomic layer deposition (ALD) methods were used to prepare the NCD and alumina films, respectively. Sliding wear tests were conducted at room temperature (RT), 300 and 450 degrees C in air. Independent of type of specimen, superlubricating behavior with the coefficient of friction (COF) in the range of 0.0040.04 was found for the tests at 300 degrees C. However, the COF value measured on the Al2O3/NCD films in the tests at 450 degrees C is lower than that for the NCD film. A relatively short run-in period and a stable COF value of about 0.15 were observed at this temperature for the Al2O3/NCD films. The width of the wear scars measured on the Al2O3/NCD films after the tests at 450 degrees C is significantly smaller in comparison with the NCD film. The apparent wear volume of the wear scar on the NCD film tested at 450 degrees C was noticeably higher than that on the Al2O3/NCD films.