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

A new multiple chemical pre-treatment including microwave oxidation, reacti on in alkaline solution and cleaning by ultrasonic treatment in acid soluti on has been performed for free shape cemented WC-Co tools in order to incre ase the diamond nucleation and to enhance the coating adhesion. High qualit y diamond films were deposited on such pre-treated substrates by a hot fila ment chemical vapor deposition (CVD) method using a mixture of acetone and hydrogen gases. After pre-treatment, the surface of the WC-Co substrate bec omes slightly rough, but its composition or structure shows no changes iden tified by X-ray diffraction (XRD). Scanning electron microscopy (SEM) indic ates a distribution of uniform micro-roughness WC grains on substrate surfa ce. The results show that the multiple chemical pre-treatment effectively i ncreases the diamond nucleation as well as greatly enhancing the coating ad hesion. Especially, it is suitable for free-shape substrates, which may ope n the way to the use of diamond coatings for coated tool applications. (C) 2000 Elsevier Science S.A. All rights reserved.