Microstructure Evolution and Mechanical Properties of Friction Stir Metal Deposited SS304

The objective of this work is to analyse the microstructure and its effect on mechanical properties of friction stir deposited SS304. Friction stir deposition is a solid-state additive manufacturing technique, where the material does not melt during the process. This process has shown potential for applications like large scale repairing of steel infrastructure. In this work, friction stir deposition of SS304 is performed at 1000 rpm rotation speed, 0.75 mm/s plunge feed rate, and 4 mm/s forward feed rate. The results suggest that a layer of about 0.5 mm thickness is deposited per pass. The continuous dynamic recrystallization and discontinuous dynamic recrystallization occurred during friction stir metal deposition. The twin boundaries observed in the as-received material are also reflected in the deposited material. The average tensile strength and ductility along the longitudinal direction of the deposited region are 647 +/- 63.5 MPa and 70.7 +/- 27.2%, respectively. The interface between the successively deposited regions is the weakest region of the deposition. This work shows the feasibility of the direct deposition of steel by friction stir metal deposition. Further, the challenge posed by the interface of the regions deposited by successive rods is highlighted.