Interface bonding characteristics and thermal damage behavior of brazed diamond with Nb-added Ni[sbnd]Cr filler alloys

Abstract

NiCr alloy is one of the important filler for brazed diamond tools because of its high hardness, high wear resistance and good wettability to diamond. However, the high brazing temperature and catalytic action of Ni element contained in alloy tend to cause the thermal damage of diamond and interface failure of brazed samples. In this work, the noval NiCr filler alloys added with different contents of Nb are prepared, and the microstructures, mechanical and wear resistance properties of brazed layers used these alloys are investigated. On this basis, the interfacial bonding characteristics and thermal damage behaviors of diamond brazed with Nb-added NiCr filler alloys are further studied. The results show that the addition of Nb element improves the hardness and wear resistance of NiCr filler layer, and the filler alloys exhibit good wettability and climbing effect to diamond. The refined Cr3C2 and Cr7C3 carbides are formed on the surface of diamond, which effectively enhances the interface bonding strength between filler alloy and diamond. Meanwhile, the addition of Nb element consumes some Ni and generates NbNi compound, which weakens, to some extent, the graphitization catalysis and chemical erosion of Ni to diamond. When the addition amounts of Nb are 1–1.2 wt%, the brazed diamond samples present excellent interfacial bonding strength and mechanical properties.