Microstructure and performance of brazed diamonds with Ni–Cr+multilayer graphene composite alloy

The aim of this paper is to provide a way of reducing unfavorable thermal damage of diamonds in the current brazing practice. To realize such objective, a new kind of composite alloy, with a relatively uniform distribution of multilayer graphene on Ni–Cr brazing filler alloy particles’ surface, was proposed to braze diamonds. Morphology of brazed samples was observed and interfacial microstructure characterization of them was analyzed. The thermal residual stress of brazed diamonds was measured by Raman spectroscopy. The mechanical performance of brazed diamonds was measured. Microstructure of alloy and brazed diamonds after etching was analyzed. The results show that the morphology of brazed diamond samples with No.1 composite alloy containing 1 wt % multilayer graphene was better. The thermal residual stress of brazed diamonds with No.1 composite alloy was decreased by 6.6%, meanwhile, the static pressure strength and toughness against impact were increased by 9% and 7.9%, respectively, in comparison with those of brazed diamonds with Ni–Cr brazing filler alloy. Cr and Ni elements were adsorbed by multilayer graphene and led to the formation of C-containing phases. The multilayer graphene layer was located between the chrome carbide layer and Ni–Cr alloy. Therefore, the unfavorable thermal damage to diamond grits was reduced by multilayer graphene.