Characterization of keyhole gas tungsten arc welded AISI 430 steel and joint performance optimization

Keyhole gas tungsten arc welding (K-TIG) is a recently developed welding process which enables single-pass welding without filler metal addition or joint preparation. Using K-TIG, 8-mm-thick AISI 430 ferritic stainless steel was successfully welded. The fusion zone of the weld was composed of columnar ferrite grains. Retained austenite was distributed along grain boundaries. The mechanical properties and corrosion resistance of the joint were tested. Three methods to enhance joint performance were trialed; high-frequency pulse arc welding (HFP-AW), austenite interlayer addition, and post-welding heat treatment (PWHT). Heat input was decreased by 42.24% when using HFP-AW. The addition of an austenite interlayer led to primary columnar austenite generation. Carbon precipitated and martensite diffused evenly into the matrix when using PWHT. The mechanical properties and corrosion resistance of the enhanced joints improved. In particular, the tensile properties of the PWHT joint and the corrosion resistance of the joint with the austenite interlayer were better than those of the base metal.