Multiscale consideration of mechanism revealing in diamond brazing with a novel NiTiZrCrVAl amorphous filler alloy: First-principles and experimental perspective

Ni-based filler alloys are extensively used in brazing diamond tools due to their superior mechanical strength and exceptional wettability to diamond. Nevertheless, the high content of the catalytic element Ni and the high brazing temperature easily lead to graphitization and thermal degradation of diamonds. This paper presented the design of novel high-temperature nickel-based amorphous brazing filler alloys with low content of Ni, based on the combining of the first principles and the theory of the “cluster-plus-glue-atom model”. The interfacial bonding mechanisms between brazed diamond and the amorphous filler alloys were examined at atomic and electronic levels using first-principles calculations. Finally, the diamond brazing experiment was carried out with this novel filler. The calculation results for the diamond/filler interface and diamond brazing experiment both show that Zr and Cr more easily transfer from the filler matrix to the interface, V atoms tend to segregate in the noninterface region and promote interface atoms bonding. Adhesion work calculations revealed that Zr, Cr, V, and Al significantly improve the interfacial bonding strength and stability between diamond and Ni-based filler alloys. Meanwhile, the experiments show that the Zr, Cr, V, and Al replaced in the filler reduces the catalytic effect of Ni on diamond graphitization. Finally, the reaction mechanism between diamond and filler alloy was clarified based on experiments and calculations.