Pre-treatment for diamond coatings on free-shape WC–Co tools

Abstract A new multiple chemical pre-treatment including microwave oxidation, reaction in alkaline solution and cleaning by ultrasonic treatment in acid solution has been performed for free shape cemented WC–Co tools in order to increase the diamond nucleation and to enhance the coating adhesion. High quality diamond films were deposited on such pre-treated substrates by a hot filament chemical vapor deposition (CVD) method using a mixture of acetone and hydrogen gases. After pre-treatment, the surface of the WC–Co substrate becomes slightly rough, but its composition or structure shows no changes identified by X-ray diffraction (XRD). Scanning electron microscopy (SEM) indicates a distribution of uniform micro-roughness WC grains on substrate surface. The results show that the multiple chemical pre-treatment effectively increases the diamond nucleation as well as greatly enhancing the coating adhesion. Especially, it is suitable for free-shape substrates, which may open the way to the use of diamond coatings for coated tool applications.