Interfacial microstructure and mechanical properties of tungsten alloy/steel diffusion bonding joint using CrFeCoNiCu high entropy alloy interlayer

In this paper, an innovative design of CrFeCoNiCu high entropy alloy (HEA) interlayer was selected to produce high-strength diffusion bonding joints of 93W-4.9Ni-2.1Fe tungsten alloy (93W, wt%) and 30CrMnSiNi2A steel (steel, wt%). The microstructure evolution and mechanical properties of the joints bonded at different temperatures were investigated. At the 93W/HEA interface, a curved and continuous μ-Fe7W6 type layer with high-density stacking faults was found in the diffusion zone between W particles and HEA, whereas the diffusion zone between γ-(Ni, Fe) phase and HEA was dominated by solid solution, companied by some nano-μ phase precipitation. The sluggish diffusion effect of HEA effectively inhibited the formation and growth of μ layer, despite the fact that the thickness of μ layer increased with the increasing of bonding temperature. Meanwhile, rod-like Cr7C3 phase and nano-granular Cr23C6 phase were found in the matrix phase of HEA near the HEA/steel interface. These chromium carbides coarsened and decreased with the increasing of bonding temperature. The strength of the bonded specimens is as high as 592 MPa at the bonding temperature of 950 °C. This study provides a new design strategy of interlayer for producing high-performance tungsten alloy/steel composites.