Effect of target power on microstructure, tribological properties of the graphite-like carbon based nanocomposite coating

Abstract The graphite-like carbon (GLC) based nanocomposite coating have attracted great attention in tribology, however, its high-temperature tribological behavior is not well investigated. In this study, the GLC-based nanocomposite coatings with different target power by direct current magnetron sputtering were fabricated, and the influence of target power on microstructure, tribological property of these coatings was investigated. The results indicates that these coatings show the graphite-like carbon (with doped nitrogen atom)/amorphous-(Si3N4, TiO2, Ti2O3)/nanocrystalline-TiC structure. With the target power increasing, the content of TiC nanocrstallines fluctuates, yet the carbon content basically is unchanged. The hardness and wear resistance are related to the ratio of nanocrystallines to amorphous phase. The maximum hardness of as-deposited coatings is about 18 GPa. The minimum COF (coefficient of friction) of coatings sliding against Al2O3 was 0.22, and the lowest wear rate is 3.2 × 10−5 mm3/(N·m). At elevated temperature, due to the cracks and the transformation in graphite-like carbon from the sp2 bond carbon clusters (sp2-C) to sp3 bond carbon clusters (sp3-C), the load-bearing capacity becomes worse, and the carbon clusters deteriorate with increasing temperature, resulting in higher COF and wear rate.