Microstructures and properties of friction stir welded 409L stainless steel using a Si3N4 tool

Friction stir welding (FSW) was performed on 409L ferritic stainless steel using a silicon nitride (Si3N4) tool. FSW was performed at a tool rotation speed of 700 rpm and a travel speed of 60 mm min−1. In this study, the microstructural characteristics, mechanical properties, and corrosion properties in the weld were examined. The stir zone (SZ) had equiaxed grains with ferrite structures due to dynamic recrystallization. Any precipitates, such as Cr-carbide (CrxCy), were not observed in the SZ and heat affected zone (HAZ). The joint had similar intergranular corrosion resistance as that of the base metal (BM) due to the non-sensitive HAZ during welding. Also, the mass loss of the joint by pitting corrosion was similar to that of the BM. The mechanical properties in the weld were similar to that of the BM. In this regard, FSW is a proper welding process for 409L stainless steel.