Diamond films were grown on WC Co cemented carbide and Si 3N 4 ceramic
cutting tool material by hot filament assisted
chemical vapour deposition. The adherence properties of the films on the substrate and the failure mechanisms of the films under pressure stress were measured and their correlations were analyzed. Carbon source was led in the system early and late, so that there existed mechanical interlocking or chemical interlocking between diamond films and cemented WC, and interfacial phases were loose graphite carbon or WC that formed again during deposition. This results in weak film substrate adhesion and delamination of diamond films under the condition without applied stress. There existed a relatively high
adhesive strength between diamond films and Si 3N 4 ceramic. Under pressure stress, the failure mode of diamond films deposited on the surface of cemented WC was film breakthrough at a small area and flaking over larger areas, while the failure mode of the diamond films deposited on the surface of Si 3N 4 ceramic was film crack formation and breakthrough at a small area.