Adherent diamond coatings on cemented carbide substrates with different cobalt contents

A new process has been employed for preparing diamond coatings on cemented carbide substrates. Before depositing the diamond coatings, a diffusion barrier interlayer was prepared by solid diffusing boron into the substrates and this interlayer has the function of suppressing catalytic effect of Co on non-diamond formations. It was confirmed that on cemented carbide substrates with Co contents ranging from 3 to 8%, high quality adherent diamond coatings could be deposited. The formation of the boronized interlayer changed the catalytic character of the substrate surface and the interlayer functioned as a diffusion barrier layer against outward Co diffusion. The latter beneficial effect was found to be accompanied by phase transformations in the interlayer, from one composed of mainly WC, CoW2B2, and CoB phases to that of CoWB, WC and Co2B phases, during the high temperature diamond deposition processes. (C) 2001 Elsevier Science B.V. All rights reserved.