Preparation and performance of diamond coatings on cemented carbide inserts with cobalt boride interlayers

Abstract

Abstract A novel two-step process has been developed, with a view to improving the reproducibility of techniques for preparing diamond-coated cemented carbide inserts. Firstly, diffusing boron into WC–6% Co inserts produced an interlayer of cobalt boride, and then diamond films were deposited on this interlayer using a DC arcjet plasma system. Investigations showed that the formation of the cobalt boride interlayer favored the growth of high quality diamond films, and the interlayer functioned effectively as a diffusion barrier layer, inhibiting outward Co migrations from the insert interior to the surface. Adhesion of the boronized interlayers as well as the composite coatings was evaluated by using Rockwell A indentation and end-milling tests, respectively. It was demonstrated that both the Co–B interlayer and the diamond coating thereon were very adherent to the substrates, and a 10-fold increase in tool life could be expected with the coated inserts compared with uncoated ones.