Structure and strength of the interphase zone during the thermochemical interaction of diamond with transition metals

The results of the study of the interphase zone structure formation features during the contact thermochemical interaction of diamond with transition metals, iron and titanium, are presented in the article. Wherein, the temperature-time modes of diamond-metal contact pairs sintering corresponded to the operating conditions of a vacuum furnace during the sintering of carbide matrixes of diamond-containing tools with copper impregnation. Shear tests were carried out to evaluate the strength of the diamond-metal contact pairs. Scanning electron microscopy, Energy dispersive X-ray analysis, X-ray diffraction analysis, and Raman spectroscopy were used to study the structure, phase composition, and morphology of interfaces. It was established that a thin layer of metal-carbide coating at the interphase boundary forms, firmly adhering to the surface of the diamond, during contact thermochemical interaction of diamond with iron. The thickness of the coating is ~ 1-3 μm and consists phases of iron, iron carbide and local, point formations of graphite. A metal-carbide coating consisting of titanium and titanium carbide phases, weakly adherent to the diamond surface was also detected at the interphase boundary of the diamond-titanium contact pair. The coating thickness is ~ 0.8-1 μm and has a dense fine-grained structure. The absence of graphite both on the surface of the diamond and on the surface of the titanium tablet indicates that all the graphite formed as a result of the catalytic action of titanium to the diamond goes to the formation of a metal-carbide coating. The obtained results can be used in the development of new compositions and technologies for manufacturing diamond tools based on carbide powder mixtures with increased diamond retention.