Diamond Brazing Diamond and Metal Bonding

Diamond Brazing Using a Cu₃₅Ni₃₅Cr₁₀Fe₁₀Sn₁₀ High-Entropy Alloy Filler

A novel high-entropy alloy (HEA) filler, Cu₃₅Ni₃₅Cr₁₀Fe₁₀Sn₁₀, with a relatively low melting point of 935 °C, has been developed for diamond brazing. Compared to conventional NiCr-based fillers, this HEA exhibits several technical advantages, including excellent wettability (contact angle of 11° on graphite), strong interfacial bonding, minimal thermal damage, and enhanced mechanical performance. Brazing can be performed at a reduced temperature of 1000 °C, significantly lower than that required for traditional fillers, thereby reducing surface damage to the diamond.

The solidified filler microstructure consists of three primary solid solution phases—FeCrNi-rich, CuNi-rich, and CuSnNi-rich—formed via liquid phase separation, alongside minor nanoscale FeCr-rich precipitates. At the diamond interface, only Cr₃C₂ and Cr₇C₃ carbide layers are formed, avoiding the formation of brittle, complex reaction products typically seen with NiCr fillers. These clean and well-bonded interfaces lead to improved fracture strength and wear resistance. This work highlights the potential of high-entropy alloys as advanced filler materials for high-performance diamond brazing applications.