Investigating the Effects of Repair Welding on Microstructure, Mechanical Properties, and Corrosion Behavior of IN-939 Superalloy

This study aimed to investigate the effects of tungsten inert gas (TIG) repair welding on microstructure, mechanical properties, and corrosion resistance of Inconel 939. After welding with Inconel 625 filler under argon atmosphere, the microstructure, hardness, tensile strength, and corrosion resistance of the specimens were analyzed. The results showed that the hardness value and corrosion resistance decreased in the heat-affected zone and particularly in the fusion zone. These changes were attributed to a decrease in the amount of gamma' phase in the fusion zone, the generation of liquation cracking, and the accumulation of dislocations. Also, the cyclic hot corrosion tests were conducted on the specimens prepared from the base metal and the weldment in a synthetic molten salt environment for 30 h at 900 degrees C, which corresponds to the operating temperature. The results showed that although the weldment remained unchanged by the end of the test, in contrast, the base metal began to change after initial cycles, and a brittle oxide layer formed on the surface. Finally, the results of hot tensile tests performed at 900 degrees C showed that TIG welding has limited effects on yield strength and elongation. Welding reduced the yield strength and elongation as much as 4 and 47%, respectively, of those of the BM.

Automated summary

This study investigated the effects of TIG repair welding on the microstructure, mechanical properties, and corrosion resistance of Inconel 939. The results showed that hardness and corrosion resistance decreased in the heat-affected zone and fusion zone due to decreased gamma' phase, liquation cracking, and dislocation accumulation. Furthermore, hot corrosion tests revealed changes in the base metal but not in the weldment, with the formation of a brittle oxide layer on the surface. TIG welding had limited effects on the yield strength and elongation of the material.