Strength of the Diffusion Bonded Joints between CP Ti and 304 Stainless Steel Processed below and above .BETA.-Transus

Abstract

Diffusion bonding was carried out between commercially pure titanium and 304 stainless steel in the temperature range of 800-900°C for 9 ks under uniaxial load in vacuum. The transition joints thus formed are characterized by optical metallography, scanning electron microscopy and tensile testing. The scanning images reveal the presence of different reaction bands in the diffusion zone and the composition of these bands were determined by energy dispersive spectroscopy. The concentrations of chemical species in the layers indicate the formation of intermetallics like a, λ, X and FeTi in the reaction zone and they were confirmed by X-ray diffraction technique. Highest bond strength (71 % of that of cp Ti) has been obtained for the diffusion-welded joints processed at 800°C owing to thinner width of brittle intermetallic phases. At high joining temperature like 900°C, strain generation near interface along with the presence of brittle intermetallics and generation of micro-voids are responsible for lowering the bond strength of the transition joint.