Interface characteristics and mechanical properties of vacuum-brazed diamond with Ni–Cr+W composite filler alloy

In this study, the diamond was vacuum-brazed to AISI 1045 steel using Ni–Cr + W composite alloy in a high-vacuum furnace. Tungsten in alloy reduces the covering of diamond, leading to the increase in its exposed height. Mechanical performance tests confirmed that static pressure strength and impact toughness of diamond brazed using Ni–Cr + W composite alloy are 18% and 7% higher than those of diamond brazed using common Ni–Cr alloy, respectively. Moreover, the degree of graphitization of the diamond brazed with Ni–Cr + W composite alloy decreases, and its thermal residual stress gets reduced by 11%. Scanning electron microscopy system equipped with energy-dispersive spectrometer and X-ray diffraction were used to investigate interfacial microstructure of brazed diamond. Results indicate that metallurgical bonding is still formed between diamond and composite alloy, so that diamond grains exhibit a high holding force. Furthermore, tungsten can react with both the diamond and the alloy without causing any separation in brazed joint. At the same time, tungsten combines with a certain amount of nickel, which reduces graphitization degree of diamond and improves its integrity.