Microstructure characterization and properties of carbon steel to stainless steel dissimilar metal joint made by friction welding

Abstract Dissimilar metals of 1045 carbon steel and 304 stainless steel are joined successfully by friction welding. The microstructure variation and mechanical properties are studied in detail. The weld interface can be clearly identified in central zone, while the two metals interlock with each other by the mechanical mixing in peripheral zone. On carbon steel side, a thin proeutectoid ferrite layer forms along weld interface. On stainless steel side, austenite grains are refined to submicron scale. The δ -ferrite existing in stainless steel decreases from base metal to weld interface and disappears near the weld interface. Severe plastic deformation plays a predominant role in rapid dissolution of δ -ferrite compared with the high temperature. Carbide layer consisting of CrC and Cr 23 C 6 forms at weld interface because of element diffusion. Metastable phase CrC is retained at room temperature due to the highly non-equilibrium process and high cooling rate in friction welding. The fracture appearance shows dimple fracture mode in central zone and quasi-cleavage fracture mode in peripheral zone. Further analysis indicates that welding parameters govern tensile properties of the joint through influencing the thickness of carbide layer at weld interface and heterogeneous microstructure in thermo-mechanically affected zone on carbon steel side.