Diamond coating on WC-Co and WC for cutting tools

Cemented carbide (WC-Co) and hot-pressed tungsten carbide (WC) were diamond coated at 850-950°C by the microwave plasma chemical vapour deposition method for use as cutting tools. First, WC inserts without Co were diamond coated utilizing the decarburization method to roughen the surface before diamond deposition. Accordingly, the absence of Co improved the adhesion strength with diamond films, which enabled the machining of Al-Si alloys with a sufficient lifetime. Similarly, the decarburization method was applied to WC-6 wt.%Co inserts and their cutting performance was compared with that of diamond-coated WC. The diamond-coated WC-6%Co inserts showed quite high adhesion strength, enough to cut Al-Si alloys for practical purposes, although slightly inferior to that of diamond-coated WC.