Effects of TIG Welding Parameters on Crack Sensitivity and Solidification Process for Co-Based Superalloys

Cobalt-based superalloys represent an innovative class of high-temperature materials. This study investigates the impact of tungsten inert gas (TIG) spot welding parameters—specifically, welding current, decay time, and preheating—on the microstructure and solidification process of the weld pool. The results indicate that increasing the welding current and decay time leads to longer and wider cracks in the fusion zone (FZ) while reducing the occurrence of fine cracks in the heat-affected zone (HAZ). Under constant welding current and decay time, preheating diminishes the weld pool area and further decreases fine cracks in the HAZ. The final microstructure of the FZ is observed to transform from equiaxed crystals to columnar dendrites and honeycomb crystals, whereas the HAZ microstructure changes from columnar dendrites to flat crystals.