酸化現象を利用した超硬合金放電加工面の改質 : 加工変質層除去機構の解明

概要

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Recently, the use of cemented carbides has become widespread for various kinds of metal molds because of their superior wear and heat resistance. However, heat-affected zones (HAZ), in which there are many cracks and microcraters, are generated by electrical discharge machining (EDM) of cemented carbides during the metal mold manufacturing process. A surface modification method using high-temperature oxidation of the surface of cemented carbides has already been proposed as a removal method for HAZ. In this study, both the high-temperature oxidation phenomenon and the removal mechanism of the HAZ were experimentally examined to clarify this modification method in detail. As a result, it was found that tungsten carbide WC can be decomposed into tungsten and carbon when the temperature is raised to about 620℃, and that carbon separated from WC reacts with oxygen in air to form carbon dioxide gas. The oxidized layer is composed of cobalt oxide CoO, tungsten oxide WO_3,and their compound oxide CoWO_4,and finally the oxidized layer can be easily removed by rubbing with a wire brush.
公益社団法人精密工学会の論文
1999-10-05