Effects of Cu, Sn, and Ti doping on the interfacial properties of Ag-based filler metal/WC: First-principles study and experimental characterization

First-principles calculations were used to determine the formation energy, work of adhesion, and electronic structure of the interface of Ag-doped (Cu, Sn, and Ti)/WC, revealing the effect of doping atoms on the interfacial bonding behavior. Additionally, an active brazing filler Ag–Cu–Sn–Ti was developed from the calculation results and applied to braze YG18 cemented carbide/40Cr steel joint. The interfacial structure and elemental diffusion behavior at the brazing filler/WC interface were characterized. The doping of Cu and Ti at the interface contributes significantly to the stability of the interfacial structure and the improvement of the work of adhesion. The effect of doping of Sn atoms at different positions on interfacial stability and the work of adhesion is not obvious, and it can be doped into Ag alloys as a melting point depressant. The charge accumulation zone and atomic orbital hybridizations at the interface contributes to enhance the interface stability and the work of adhesion. The TEM analysis demonstrates that the diffusion behavior of Ti is particularly noticeable, aggregating at the Ag/WC interface and interacting with C to generate a TiC reaction layer, ultimately producing a WC/TiC/Ag interface structure.