Study on the microstructure and properties of brazed diamond with Nb2O5-added NiCr filler alloy

Abstract

This study systematically investigates the microstructure, diamond thermal damage and grinding performance of brazed diamond with pure NiCr, Nb-added, and Nb₂O₅-added NiCr filler alloy, combining high-temperature brazing experiments with the first-principles calculations. The experimental results showed that compared to pure NiCr filler alloy, both Nb and Nb₂O₅ addition improve the overall performance of brazed diamond, with Nb₂O₅ showing a more significant modification effect. The Nb₂O₅-added NiCr filler alloy induces the formation of NbNi and B₂O₃ in the brazing layer, which effectively inhibit diamond graphitization by mitigating the catalytic effect of Ni at the interface and reducing the formation of hard and brittle phases (e.g., Ni₃B, CrB, etc.). This helps to prevent crack initiation at the diamond-brazed filler alloy interface. Furthermore, Nb₂O₅ enhances chemical reactions between Cr and C at the brazed diamond interface, resulting in the formation of structurally refined CrC carbides at the interface, which strengthen the interface bonding. First-principles calculations reveal that the interfacial work of separation for the Nb₂O₅-added NiCr filler alloy system increases by 2.04 J/m² and 0.28 J/m², compared to the pure NiCr and Nb-added NiCr filler alloy systems, respectively. The coexistence of Nb and O enhances electron cloud overlap between Cr and C atoms at the interface and reduces the peak at the of Fermi level for C layer, indicating the stronger interfacial bonding and the lower graphitization of diamond.