Effects of reaction products on the bond strength of the transition joint formed between titanium and stainless steel

Abstract

Solid state diffusion bonding was carried out between commercially pure titanium and 304 stainless steel in the temperature range 800 - 950°C for 120 min in vacuum under uniaxial load. The transition joints were characterised using optical and scanning electron microscopy. The study shows the presence of different reaction layers in the diffusion zone and their chemical compositions were determined by energy dispersive spectroscopy. The occurrence of different intermetallic phases such as FeTi, λ, χ, and σ has been predicted from the ternary phase diagram of Fe - Cr - Ti and they were confirmed by the X-ray diffraction technique. A maximum bond strength 76% of that of titanium was obtained for the diffusion couple processed at 800 ° C owing to finer size intermetallic compounds and the increment in joining temperature, which results in growth of brittle intermetallics leading to a sharp fall in the strength of the transition joints.