Microstructure and mechanical properties of Inconel 600 nickel-based alloy PAW + TIG joints

Addressing the welding challenges of Inconel 600 nickel-based alloy in the petrochemical equipment industry, selecting an appropriate welding process is challenging. A 6 mm thick Inconel 600 nickel-based alloy is welded using the PAW + TIG process. The microstructure and mechanical properties of the Inconel 600 nickel-based alloy PAW + TIG joints are studied using optical microscopy, scanning electron microscopy, and tensile testing machine. Microstructure analysis shows that the joint weld surface is smooth and even, with a semi-elliptical fish scale pattern uniformly distributed. Both the base material area and the heat-affected zone exhibit fine equiaxed austenite crystals, with the grain size in the heat-affected zone being larger than in the base material area. The weld zone has a dendritic structure. The tensile strength of the joint reaches 589 MPa, and the fracture type is ductile, indicating good plasticity and bending resistance of the welded joint. Electrochemical corrosion tests at the weld indicate increased localized corrosion sensitivity in the heat-affected zone, suggesting reduced corrosion resistance of the welded joint. Post-weld annealing and performance testing shows that annealing precipitated needle-like second phases, forming a certain strengthening effect at grain boundaries and twin boundaries, which can inhibit grain growth and affect the overall performance of the material. A comprehensive analysis of the microstructure and performance of the welded joints shows that the PAW + TIG joints have good thermal stability, meeting the requirements for high-temperature operation.