Influence of Immersion Corrosion on Mechanical Properties of AISI ۴۳۰/AISI ۳۱۶L Dissimilar Welded Joints

Dissimilar welded joints of AISI ۴۳۰ and AISI ۳۱۶L stainless steel were produced by the GMAW process using two different shielding gas mixtures composed of ۹۷Ar-۳N۲ and ۸۰Ar-۱۹He-۱O۲. The microstructure of the heat-affected zone was characterized by optical and scanning electron microscopy, and Vickers microhardness measurements were carried out along the cross-section of the specimens. The dissimilar welded joints were submitted to immersion corrosion test in a ۱۰%v/v hydrochloric acid solution for ۲۴ and ۷۲ hours. Afterward, yields strength, tensile strength, and elongation percentage were measured using tensile tests according to ASTM E۸ standard. Non-immersed welded joints were used for comparison purposes. An analysis of variance was developed to evaluate the influence of immersion time and shielding gas mixture on yielding strength and tensile strength. The microstructure characterization showed that the heat-affected zone on AISI ۴۳۰ side was the widest, and it was observed a significant presence of acicular ferrite, martensite, and coarsened ferritic grains. In contrast, on the heat-affected zone on AISI ۳۱۶L side was not observed coarsening nor refinement of austenite grains. The AISI ۴۳۰ heat-affected zone showed the maximum hardness values and higher susceptibility to corrosion damage. Tensile tests results evidenced that immersion corrosion tests did not change significantly ultimate strength in comparison to non-immersed specimens while yielding strength and elongation percentage were drastically decreased due to immersion time. According to the p-value, the immersion time is the most influencing factor on yielding strength and tensile strength of the dissimilar welded joints.

Keywords:

Dissimilar Weldedjoints , Stainless steel , corrosion , Tensile test , Heat-affected zone