CVD diamond coating on WC cutting tool using electrophoresis

CVD diamond films were deposited on commercial WC cutting tools. An electron cyclotron resonance micro-wave plasma chemical vapor deposition (ECR-MPCVD) apparatus was used to deposit diamond films. Methane and hydrogen were used as gaseous source for CVD, and WC-Co (JIS standard: K-10) was used as a substrate for CVD. Cobalt on the surface of the WC cutting tool prevented CVD diamond from depositing on the WC cutting tool. Scratching with diamond particles on the surface of the WC cutting tool, which is one of the most popular pretreatments for enhancing the nuclei density of CVD diamond, was ineffective on the WC cutting tool without removing surface cobalt. On the other hand, Electrophoresis treatment was effective for increasing diamond nuclei density on the WC cutting tool without removing surface cobalt. However, CVD diamond films synthesized on the WC cutting tool (from which surface cobalt was removed) using electrophoresis pretreatment separated from the surface of the WC cutting tool. To improve the adhesion between CVD diamond film and WC cutting tool, heat treatment was performed after electrophoresis pretreatment. The heat treatment condition was 500°C for 1 h in Ar flow. The heat treatment after electrophoresis treatment was effective for improving adhesion between WC surface and CVD diamond film. Vickers hardness test was carried out for estimating the adhesion. The Vickers hardness of the CVD diamond film obtained by the electrophoresis-heat pretreatment, was as hard as that of a CVD diamond film obtained with conventional scratching pretreatment. From the results of Vickers hardness test, it was found that heat treatment after electrophoresis process is effective for improving the strength of the adhesion layer.