A comparison in performance of diamond coated cemented carbide cutting tools with and without a boride interlayer

Instead of depleting cobalt from the surface of cemented carbide substrates or introducing a cobalt-free interlayer between the substrates and diamond coatings, a boride interlayer could be employed to modify the catalytic characteristics of cobalt in the substrate surface, preventing cobalt from interfering with the deposition of diamond coatings. This paper compares deposition of diamond coatings and performance of diamond coated cemented carbide cutting tools, with and without such a boride interlayer. We will show that a profound effect of using the interlayer is that it allows the deposition of adherent diamond coatings within a relatively broad temperature range, which improves reproducibility of the coating processes. With the interlayer present, an increase in tool life of 20-fold has been obtained, in comparison with that of uncoated tools. Such an increase in tool life can be attributed to the improved adhesion of the diamond coatings.