Influence of annealing temperature on thermal stability and tribological properties of diamond-like carbon coatings

The diamond-like carbon (DLC) thin films, deposited on substrates of SiC balls and high speed steel discs by unbalanced magnetron sputtering, were annealed in ambient environment. The impact of the annealing temperature on the microstructures, thermal stability and tribological behavior of the DLC coatings was investigated with metallographic microscope, Raman spectroscopy, and conventional mechanical probes. The results show that the annealing temperature significantly affects the microstructures, thermal stability and tribological property of the DLC coatings. To be specific, as the annealing temperature increased, the sp³-C bond rapidly turned into sp²-C bond, and the friction coefficient and wear-rate changed in an increase-decrease mode, being the lowest at 400^oC. Annealed at 600℃, a significant diamond-to-graphite transition occurred. In the wear tracks, the SiC scraps observed in the wear tracks possibly account for the reduction of both the friction coefficient and wear rate.