Investigations on the microstructure, mechanical properties and corrosion resistance of SUS 304 austenitic stainless steel welded joints by pulsed current gas tungsten arc welding

Abstract

In the present research work, the joining of 3 mm thick sheets of SUS 304 stainless steel (SS) was addressed by pulsed current gas tungsten arc (PCGTA) welding techniques with ER308L filler wire, which came to a connection between the microstructure of the welds and the resultant mechanical and corrosion behavior. The main focus of the study involved the investigation on the effect of filler wire on welding quality of butt joints obtained. Trial experiments were carried out to find whether or not the proper filler wire was added could exert a great influence on the depth of penetration. The studies turned out that a full and sound penetration could be achieved with filler. Microstructure observations divulged the formation of different zones across the weldments, austenite/δ-ferrite at the weld zones (WZ), austenitic coarsening and growth at the heat affected zones (HAZ). Mechanical testing showed that better tensile properties and microhardness accrued in the filler weldments (FW) due to the presence of δ-ferrite and secondary phases which need further investigation, whose average tensile strength and maximum microhardness were 569 MPa and 392 HV respectively. For no filler weldments (NFW), its mechanical performances were distinctly inferior to FW. According to the electrochemical test results, base metal (BM) displayed the best corrosion resistance because it was far from such sources of pitting corrosion. Based on both passivation potential and breakdown potential, the ranking for corrosion resistance was: BM > FW > NFW. Practice proved that the results of the current study would also help in obtaining high-quality butt joints of SUS 304 SS sheets based on traditional PCGTA welding with ER308L filler wire.