Effect of heating in air or vacuum on the delamination strength of WC-Co coating deposited by high-velocity flame spraying
Zhang Dongkun; Kato Masahiko; Nakasa Keijiro; Tasaka Keiichiro
Abstract:High-velocity flame spraying of WC-Co cernet was applied on a tool steel substrate (JIS:SKD5). After the specimens were heated in air or vacuum, edge-indentation tests of the specimens were carried out to examine the change of delamination energy. For the specimens heated at 773 K in air or vacuum within 144ks, delamination load did not change. When the heating temperature was 873K and hold time was longer than 144ks, the delamination load decreased. Delamination area decreased when the hold time exceeded 3.6ks. Delamination energy E sub d of the specimen heated at 773K increased with increasing hold time within 144ks without decreasing hardness of coating and substrate, and the E sub d was larger for the specimen heated in air than in vacuum. The Edof the specimen heated at 873K in air increased with increasing hold time, but the hardness of coating and substrate decreased. The increase in delamination energy by heating was due to the diffusion of Fe and Co elements across the interface between coating and substrate. Key Words:WC-Co coating, high-velocity flame spraying, tool steel substrate, heating in air or vacuum, delamination stremgth