The effect of interlayer on the microstructural characteristic and mechanical properties of diffusion welding between 17-4PH steel and Ti6Al4V alloy

The aim of this study was to investigate the effect of interlayer on the microstructal characteristic and mechanical properties of diffusion welding between 17-4PH precipitation hardening stainless steel and Ti6Al4V alloy. For this purpose, the bonding of two alloys without the interlayer and with the pure nickel interlayer at a temperature of 900 ° C and a time of 45 minutes was investigated. . The structure of joints were characterized by optical microscopy, scanning electron microscopy and energy dispersive x-ray spectroscopy. After examining the microstructure and diffusion rate, the hardness and shear strength of joints were also investigated. The results show that the β-Ti, λ + FeTi and σ phases are formed at the interface when the interlayer is not used.The formation of these intermetallic compounds causes a brittle bond and reduces the mechanical properties. When the pure nickel interlayer is used, Ni3Ti, NiTi and NiTi2 intermetallic compounds are formed at the nickel-titanium interface. Nickel in the form of interlayer prevents the diffusion of titanium into iron and the formation of FeTi compounds. The maximum microhardness of 562 Vickers was obtained, which is exactly on the intermetallic compounds. The average shear strength was 289 MPa if the interlayer was used.