Characterization of Microstructure and Interface Reactions in Friction Welded Bimetallic Joints of Titanium to 304 Stainless Steel Using Nickel Interlayer

Direct joining of 304 stainless steel to titanium poses many challenges because of a lack of metallurgical compatibility and the formation of FeTi and CrTi types of brittle intermetallic compounds. The use of a low thermal heat input process of friction welding allows to obtain good microstructure properties through the improvement of metallurgical compatibility between two metals. In the present investigation, a novel approach of nickel interlayer was applied to explore a new bimetallic structure of titanium to stainless steel. Microstructure characterization, interface formation and its reactions were analysed via scanning electron microscope, X-ray diffraction and electron probe microanalyser analyses. The results exhibited that the intermetallic phases were successfully avoided through the use of Ni interlayer. Microhardness values demonstrated the absence of brittle FeTi and CrTi phases in the weld interface. The weld interface was found to be within two intermetallic layers situated at Ti/Ni interface.