Microstructure, mechanical and corrosion properties of friction stir welded high nitrogen nickel-free austenitic stainless steel

Friction stir welding (FSW) was applied to a 2.4mm thick high nitrogen nickel-free austenitic stainless steel plate using tungsten–rhenium (W–Re) tool. The high-quality weld was successfully produced at a tool rotational speed of 400rpm and a traveling speed of 100mm/min. The microstructure, mechanical and corrosion properties of the weld were studied. The nitrogen content of the weld was almost identical to that of base metal (BM). FSW refined grains in the stir zone (SZ) through dynamic recrystallization and led to increase in hardness and tensile strength within the SZ, while the ductility was slightly decreased. The failure of tensile specimens occurred in the BM. TEM results revealed precipitates of Cr23C6 of size ~1μm in the SZ, although their content was small. The precipitation of Cr23C6 and increase in δ-ferrite in the SZ led to small decrease in both pitting and intergranular corrosion resistance.