Effect of Rotational Velocity on Mechanical and Corrosion Properties of Friction Stir-Welded SUS301L Stainless Steel.

Friction stir welding was utilized to obtain high-quality SUS301L stainless steel joints, whose mechanical and corrosion properties were thoroughly evaluated. Sound joints were obtained with a wide range of rotational velocities from 400 to 700 rpm. The microstructures of the stir zone primarily consisted of austenite and lath martensite without the formation of detrimental phases. The ultimate tensile strength of the welded joints improved with higher rotational velocities apart from 400 rpm. The ultimate tensile strength reached 813 ± 16 MPa, equal to 98.1 ± 1.9% of the base materials (BMs) with a rotational velocity of 700 rpm. The corrosion resistance of the FSW joints was improved, and the corrosion rates related to uniform corrosion with lower rotational velocities were one order of magnitude lower than that of the BMs, which was attributed to the lower martensite content. However, better anti-pitting corrosion performance was obtained with a high rotational velocity of 700 rpm, which was inconsistent with the uniform corrosion results. It could be speculated that a higher martensitic content had a negative effect on the uniform corrosion performance, but had a positive effect on the improvement of the anti-pitting corrosion ability.