Theoretical assessment of dissimilar metal joint of titanium to stainless steel

Direct joining of titanium to stainless steel poses some unique challenges because of a lack of metallurgical compatibility and the formation of brittle intermetallic compounds between the two metals. In the first half of this paper, a literature review is provided to assess various existing joining methods (such as explosive welding, diffusion bonding, and brazing) utilizing different interlayer metals (e.g., copper, silver and nickel). The joint strength achieved by different methods is compared. In the second half of the paper, the in-service behaviors of the dissimilar joint are evaluated based on theoretical calculations. A finite element method based model is used to calculate the thermal-stress distribution in the dissimilar metal joint. For simplicity, the residual stresses from the joining process are not considered. In addition, the chemical stability of the joint is evaluated based on the inter-diffusion of alloying elements. It is found that the mismatch of coefficient of thermal expansion has a prominent effect on the thermal-stresses. The interlayer metal can be effective in deterring the inter-diffusion between titanium and stainless steel.