The susceptibility to weld cracking of Ta-containing cast cobalt-based superalloy Mar-M302

The susceptibility to weld hot and cold cracking of Ta-containing cast cobalt based superalloy was studied. The microstructure of welded Mar-M302 cobalt based superalloy was investigated both autogenously and by usingfiller metal. Three different kinds of cracking were observed in the welded samples. It was found that; very hard and brittle eutectic has significant effects on base metal cracking during welding. The special type of microcracking observed in the eutectic, located in the heat affected zone(HAZ) of autogenous welds. Also the results revealed that when angular strains increased to the base metal elongation level, the cold macrocracks happened in filler metal welded samples in the opposite side of the weld line propagating along the eutectic areas. As a result the crack free repair welding procedure was achieved with controlling the metallurgical and mechanical parameters