Adhesion properties of arc ion-plated TiN coatings with WC particle size, Co content and surface roughness

In this work, TiN coating layers were deposited on various kinds of WC–Co substrates by an arc ion plating (AIP) method. Effects of WC particle size, Co content, surface roughness on the adhesion strength and failure behavior of the AIP-TiN/substrate interface were studied using a conventional scratch test. It was found that Co had diffused out of the substrate toward the coating layer and formed a certain phase composed of Ti and Co. This phenomenon might induce strong bonding between the coating layer and the substrate. The highest critical load, approximately 110 N, was obtained at a WC particle size of 1 μm and Co content of 10 wt.%. As the WC particle size, Co content and surface roughness of the substrate increased, the critical load was reduced. Adhesion between the coating and substrate was considerably affected by both the surface morphology of the coating and the surface roughness of the substrate.