Effect of single step pretreatment on cobalt contents and surface roughness of tungsten carbide substrate prior to diamond coating

Adhesive strength is a critical issue for super hard diamond coatings on tungsten carbide (WC-Co). The presence of Co in the cemented tungsten carbide substrate has a negative influence on the diamond deposition process. High Co content in the substrates has proved to be very deteriorating for the adhesion of diamond coatings. The surface treatments (single step pretreatment) leading to both Co removal and the roughening of the substrate surface can ensure adequate adhesion levels of the diamond coatings deposited onto WC-Co substrates. The factors investigated were acid temperature, etching time, concentration of H2O2 and concentration H2SO4. The Co content and surface roughness were the response variables investigated. The experimental plan was based on the face central composite design (CCD). The experimental results indicate that the proposed mathematical models suggested could adequately describe the performance indicators within the limits of the factors that are being investigated. The acid temperature is the most significant factor that influences the surface roughness and the Co content. The etching time provided secondary contribution to the responses investigated. Additionally, the square of the acid temperature also provided secondary contribution to the surface roughness. The reduced quadratic model developed using RSM were reasonably accurate and can be used for prediction within the limits of the factor investigated.