Effect of boron segregation at grain boundaries on heat-affected zone cracking in wrought INCONEL 718

Susceptibility to heat-affected zone (HAZ) cracking during electron-beam we lding was studied in two INCONEL 718-based alloys doped with different leve ls of boron, By lowering the carbon, sulfur, and phosphorous concentrations to be "as low as possible," the occurrence of HAZ cracking was related dir ectly to the level of segregation of boron at grain boundaries, which occur red by nonequilibrium segregation during a preweld heat treatment. The stud y has demonstrated a direct correlation between the amount of boron segrega ted at grain boundaries and their susceptibility to HAZ cracking, in terms of the total crack length and number of cracks observed in the HAZ. The ana lysis of results suggests that both the melting and resolidification temper atures of the boron-segregated grain boundaries can be about 100 degreesC t o 200 degreesC lower than those of the grain boundaries that were susceptib le to constitutional liquation of Nb carbides on them, making boron more de leterious in causing HAZ cracking.