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The purpose of this study is to determine the effects of post-annealing and post-tempering processes on the microstructure, mechanical properties and corrosion resistance of the AISI 304 stainless steel gas metal arc weldment.

Gas metal arc welding of AISI 304 stainless steel was carried out at an optimized processing condition. Thereafter, post-annealing and post-tempering processes were performed on the weldment. The microstructure, mechanical and electrochemical corrosion properties of the post-weld heat treated samples, as compared with the as-welded, were investigated.

The as-welded joint was characterized with sub-granular grain structure, martensite formation and Cr-rich carbides precipitates. This made it harder than the post-annealed and post-tempered joints. Because of slower cooling in the furnace, the post-annealed joint contained Cr-rich carbides precipitates. However, the microstructure of the post-tempered joint is more refined and significantly devoid of the carbide precipitates. Post-tempering process improved the elongation (∼23%), tensile (∼10%) and impact (∼31%) strengths of the gas metal arc AISI 304 stainless steel weldment, while post-annealing process improved the elongation (∼20%) and impact strength (∼72%). Owing to the refined grain structure and significant elimination of the Cr-rich carbide precipitates at the joint, the post-tempered joint exhibited better corrosion resistance in 3.5 Wt.% NaCl solution than the post-annealed and the as-welded joints.

The appropriate post-weld heat treatment that enhances microstructural homogeneity and quality of the AISI 304 gas metal arc welded joint was determined.

The purpose of this study is to conduct gas tungsten arc dissimilar welding of AISI 304 stainless steel and low carbon steel within a process window so as to investigate the effects of current, speed and gas flow rate (GFR) on the microstructure and mechanical properties of the weldments.

The welding experiment was carried out at different combinations of parameters using WN-250S Kaierda electric welding machine. A combination of scanning electron microscopy and energy dispersive X-ray spectroscopy was used to examine the microstructure of the weldments. Micro-hardness and tensile tests were performed using Vickers hardness tester and Instron universal testing machine, respectively. ANOVA was used to analyze the significance of the parameters on the mechanical properties.

The microstructure of the weld region is characterized with dendritic structure with the existence of ferrite and austenite phases. The utilized parameters show significant effects on the ultimate tensile strength (UTS) of the weldments. The current and GFR were found to be the most and least significant factors, respectively. Both the grain size and weld penetration contributed to the UTS of the weldments. The UTS (427-886 MPa) increased with decreasing current and welding speed. In all samples, the weld region exhibited higher hardness (297-396 HV) than the HAZ in the base metals (maximum of 223 Â ± 6 HV). All the three factors show significant effect with the welding speed contributing mostly to the hardness of the weld region.

The parametric combination that gives the optimum mechanical performance of the dissimilar gas tungsten arc weldments of AISI 304 stainless steel and low carbon steel was established.