Factors Affecting Weldability Improvement of Dissimilar Welds of Aged HP Stainless Steel and Alloy 800

The microstructure of HP stainless steel in aged and aged + solution annealed conditions and solutionized alloy 800 was characterized by optical microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) equipped by EDS. All phases present in the above condition were described. The effects of solution annealing heat treatment temperature on the microstructure, tensile, hardness, toughness, and ductility of aged HP stainless steel and its weldability to alloy 800 have been discussed. In addition, the effects of heat input, interpass temperature, and type of filler metal on weldability of two alloys were investigated. It was found that during solution annealing, the precipitates produced in the aging stage are decomposed and niobium carbide (NbC) is formed. It was also observed that while tensile strength and hardness fell, ductility and toughness were improved. Dissimilar welding between alloy 800 and aged HP stainless steel was not successful and cracks were observed in the HAZ of the aged HP stainless steel, while welding alloy 800 to HP stainless steel (aged + solution annealing at 1100-1200ºC, low interpass temperature, and Inconel 82 or 617 filler metals) was successful.