Adhesion and raman studies of magnetron sputtered amorphous carbon on WC–Co

Abstract

Amorphous carbon coatings up to 2 μm thick were deposited on WC–Co substrates by magnetron sputter ing of a graphite target in Ar and Ar–H_t2 atmospheres. The Raman peak intensity ratio of the D band to the G band I_d /I_g and the G band peak shift decreased initially but subsequently increased with bias power. Chamber pressure directly influenced the adhesion and hardness of the coating. It was established that below a certain minimum chamber pressure, there was spontaneous coating detachment. X-ray photoelectron spectroscopy depth profiling was used to quantify the cobalt depletion at the substrate surface as a function of sputter cleaning bias power. It was found that scratch adhesion strength increased with sputter clean ing power and reached a maximum at about 200 W, or -210 V in terms of induced voltage. The increase in adhesion strength was attributed to better cleaning of the interface cobalt.