The Influence of Different Heat‐Treatment Temperatures on the Tungsten Inert Gas‐Welded Joints of Inconel 625 Alloy

Inconel 625 alloy exhibits excellent high‐temperature mechanical properties and corrosion resistance, making it widely used in fields such as solar thermal power plants. However, during welding, element segregation and the formation of harmful secondary phases can occur at the weld, affecting the joint performance. This study investigates the effects of various heat‐treatment processes on the microstructure and mechanical properties of Inconel 625 tungsten inert gas (TIG)‐welded joints, utilizing low‐temperature treatments at 400°C, 500°C, and 600°C, and solution treatment at 900°C, 1000°C, and 1100°C. The results show that the weld of Inconel 625 alloy consists of dendrites and fine cellular crystals, with blocky Laves phases distributed between the dendrites. After low‐temperature treatment, the grain structure of the weld shows no significant changes, and carbides (MC) begin to precipitate. When the low‐temperature treatment temperature reaches above 500°C, the carbides (MC) transform into M 23 C 6 and δ phases, resulting in an increase in joint hardness. After solution treatment, the dendrites in the weld gradually transform into equiaxed grains, and the Laves phases dissolve and solidify into the matrix, reducing element segregation. The hardness and yield strength of the treated samples are both lower than those of the untreated sample. The yield strength of the untreated sample is 37.6 MPa, and the elastic modulus is 200 GPa. After solution treatment at 1100°C for 1 h, the yield strength decreases to 26.7 MPa, and the elastic modulus decreases to 180 GPa. Considering the elimination of the secondary phases and the strength, solution treatment is determined to be the optimal heat‐treatment process for Inconel 625 TIG‐welded joints. This study provides a basis for optimizing the welding process of Inconel 625 alloy in industrial applications.