Adding Hf element to improve the strength and wear resistance of diamond brazed with Ni-based boron-free brazing filler metal

Abstract

Nickel-based filler is a very important brazing material with excellent corrosion resistance and strong hardness. However, its high-temperature thermal damage, graphitization and multiple brittle phases are still problems to be solved. In this work, the NiCrSiCuSn boron-free brazing filler metal is reinforced by adding different contents of Hf element. The microstructure of the filler and morphology of the diamond were analyzed by scanning electron microscope and energy dispersive spectroscopy. The phase composition of the brazed joint is characterized by X-ray diffraction. The alloy segments and brazed diamond segments were performed by the vickers microhardness tester and the friction and wear tester, respectively. The results show that when 1 wt% Hf is added to Ni-based boron-free filler, the melting point of the filler is the lowest and the crystal grains are also refined. At the same time, chromium carbide is formed between diamond and brazing material, so they are closely connected. Compared with other components, brazed diamond with 1 wt% Hf brazing filler metal has the best exposure, higher joint strength and wear resistance, and a lower degree of graphitization. The morphology of the bonding surface and the wear surface shows that the addition of 1 wt% Hf reduces the thermal damage of the diamond.In turn, the mechanical properties of the joint are optimized.