Improvement of microstructure and mechanical properties of stainless steel TIG based wire arc additive manufacturing by using AC/DC mix current waveform

Abstract

In this work, a new current waveform, the AC/DC mix current waveform was employed to improve the microstructure and mechanical properties of 307Si stainless steel component during the TIG based wire arc additive manufacturing (TIG-WAAM). The results showed that the morphology of γ-austenite is changed from the columnar dendrites (with DC mode) to the equiaxed dendrites (with AC/DC mix mode). The grain size was refined due to the reduction of the temperature gradient in the AC/DC mix mode. The degree of refinement grain is increased with the increase of AC ratio. The tensile strength of the 70%DC+30%AC-sample in the traveling and building directions are respectively increased by about 60 MPa and 41 MPa compared with that of the 100%DC-sample. The grain refinement is the mainly reason of the improvement of mechanical properties of the TIG-WAAM component with the AC/DC mix mode.