Diamond Coated WC Tools for Machining Wood and Particle Board

Abstract

Diamond coating was provided to improve the performance of WC-Co tools used in machining wood and particle board. Microwave plasma chemical vapor deposition was used to deposit diamond using a gas mixture with CH4: H2 in the ratio 0.5: 100 at a temperature of 900°C. The microwave energy was set at 900W and a pressure of 35Torr was maintained in the chamber. An essential factor that determines the life of polycrystalline diamond coated tools is poor film adhesion. To counter this problem, we have developed a process that includes etching away cobalt from surface regions, treatment with H2 plasma and use of TiN/ TiC intermediate and embedding layers. The TiN/ TiC layers were deposited by reactive magnetron sputtering. These layers embed diamond crystallites and improve adhesion, and in addition act as good diffusion barriers for Co. The diamond coated and uncoated tools have been characterized in the as deposited conditions and after prescribed wear by machining particle board using SEM and X-ray mapping. It was also found that the limited contact area with diamond on the cutting edge affects the adhesion of the coating. Improvement in contact area by providing a larger radius to the cutting edge is discussed.