抄録
Recently, the use of cemented carbides has become widespread for various kinds of die making because of their great resistance to wear and heat. However, the heat-affected zones, in which there are many cracks and micro-craters, are generated by EDM of cemented carbides during the die manufacturing process. These defects remarkably decrease the strength of die and are the main cause of die damage. The present paper deals with a surface modification method using oxidizing treatment as a means of removing these heat-affected zones. This method uses a high-temperature oxidation of the surface of cemented carbides. The oxidized surface layers are soft and can be removed easily. As a result, the heat-affected zones generated by EDM can be completely removed by this oxidizing treatment. The oxidized surface comprises the oxides of cobalt and tungsten. The crystalline structures after the removal of these oxides are transformed to a hexagonal lattice of WC in a stable structure.
