Features of the interfacial zone structure formation during thermal diffusion metallization of diamond by transition metals

Abstract

The paper studies morphology, chemical, structural and phase composition of the diamond-metal interphase zone, formed in the process of thermal diffusion metallization of diamond with chromium, titanium, iron, nickel and cobalt powders with the same temperature-time mode that corresponds to the sintering of diamond-containing WC-Co-matrices with copper impregnation. In the process of thermal diffusion metallization of chromium and titanium, a metalized coating is formed on the surface of the diamond, consisting of a mixture of carbides, metals and graphite of variable composition phases. The insignificant content of graphite formations and their intermittent nature of the diamond-metal interfacial zone ensure a strong adhesion of the metalized coating to the diamond through the carbides of the corresponding metals. When thermal diffusion metallization of diamond with iron occurs at the diamond-metal interfacial zone, the formation of an intermediate layer strongly adhered to the diamond also takes place. The intermediate layer has a complex structural phase composition comprising a mixture of iron phases, a solid solution of carbon in iron and graphite of variable composition. An intermediate layer on the surface of diamond could be formed by solidification of the liquid phase with the eutectic composition resulting from the eutectic melting of the diamond-iron contact pairs. However, this assumption requires additional research to confirm it, and special experiments using highly sensitive research methods. Under the heating conditions specified in the experiment samples of nickel-diamond and cobaltdiamond cause intense catalytic graphitization of diamond with the formation of numerous traces of erosion on its surface. The observed weak adhesive interaction of these metals with diamond is probably due to the high melting temperatures of the Ni-C and Co-C eutectics, which does not allow the metals to react with diamond under given experimental conditions.