Microstructural analysis of bimetallic SS308L/Cu fabricated by wire-arc additive manufacturing

The current research comprises the fabrication of a bimetallic graded material composed of SS 308L and copper, employing the wire-arc additive manufacturing (WAAM) technology with gas metal arc welding (GMAW) machine. The experiment successfully produced a bimetallic-graded structure by depositing two copper layers over SS308L austenitic stainless steel. The deposition of SS308L entails solidification in a ferrite-austenite (FA) phase. The deposited material included ferrite phases extending to the interface of the second copper layer. The ferrite dispersion inside the copper matrix was homogeneous. At the interface, the ferrite phase has globular and dendritic morphologies, whereas the middle portion of SS308L exhibits vermicular and lathy ferrite shape. The microstructural investigation identified iron dendrites in the supersaturated copper, although no copper phase precipitation occurred inside the iron dendrites. The results indicated that microhardness values decreased from 284 HV to 106 HV when the deposition transitioned from the base metal to the copper layer in the building direction, demonstrating a significant correlation with the grain size and phase precipitation observed in the copper layers.