It was well known that cobalt plays an important role during diamond deposition on cemented carbide substrates. The presence of cobalt on the substrate lead to decrease adhesion and increase the formation of non-diamond compounds phases. However, the diffusion phenomenon of cobalt in diamond coatings was not well understood. A detailed investigation was made of the diffusion of cobalt, during the nucleation and growth of diamond on WC-Co substrates, by using the combustion-flame method, and its influence upon the structure and quality of the diamond coatings. At high substrate temperatures, Ts > 800C, ball-sharp of cobalt with a ball size about 0.7μm was observed on the top surface of diamond coatings (thickness >50μm). The constraints in the coating were very high, the Raman peak appearance at 1341.1/cm. At relatively low substrate temperature, T s was about 550C, ball sharp of cobalt was not observed by MEB but a lot of cobalt particles dissolution carbon films were detected by EDX. Based on the above results, the influence of cobalt on the structure, the quality and the constraints in the diamond films were discussed, a model suggesting the nucleation and growth mechanisms of diamond, to explain the cobalt diffusion in diamond films, was presented.

Diffusion of Cobalt in Diamond Films Synthesized by Combustion Flame Method. Donnet, J.B., Paulmier, D., Oulanti, H., Hue, T.L.: Carbon, 2004, 42[11], 2215-21