The failure mechanism of chromium as the interlayer to enhance the adhesion of nanocrystalline diamond coatings on cemented carbide

Chromium as an interlayer has been developed to enhance the adhesion of nanocrystalline diamond (NCD) coatings to cemented carbide cutting tool materials. This study showed that Cr did not play the expected role and that the NCD coating delaminated during the Rockwell C indentation test. A systematic study of the morphologies, composition, and phase components of the failed samples showed that although Cr prevented the outward diffusion of Co to the diamond interface, the chromium carbides formed during the NCD deposition contained microcracks, which provided a path for delamination in the presence of high tensile thermal stresses generated when cooling the coating to room temperature. This work provides additional criteria to choose an appropriate interlayer to enhance the adhesion of diamond coatings to cutting tool materials.