First-principles calculations on brazed diamond with FeCoCrNi high entropy alloys doped with strong carbide-forming elements

FeCoCrNi alloy is one of the most widely studied high-entropy alloys due to its excellent properties such as extreme hardness, excellent wear resistance, and good chemical stability. However, the feasibility of using FeCoCrNi alloy as the filler for brazing diamond and the related interfacial bonding mechanisms are unclear. In this work, the interfacial bonding behaviors between FeCoCrNi filler and diamond, and the influences of strong carbide-forming elements X (X = Mo, Mn, Ti, V, W, Zr, Nb, Hf, Ta) doping into FeCoCrNi filler on the brazed diamond were systematically investigated through first-principles calculations method. The calculated interfacial segregation work and interfacial energies show FeCoCrNi/diamond interface has a higher interfacial bonding strength and stability than Ni–Cr/diamond interface. The calculated embedding energies show that these strong carbide-forming elements X are more likely to segregate in the interfacial region close to the diamond. The doping of X, especially Hf, Zr, Ta, and Nb, significantly enhances the interfacial bonding strength and stability of the FeCoCrNi/diamond interface. Combining with further analysis of electronic structures, it is suggested that the FeCoCrNiNb is an ideal high entropy alloy filler for brazing diamond due to its dual effects on interface strengthening of FeCoCrNi/diamond and graphitization inhibiting of diamond.