Effect of heat input on cracking in laser solid formed DZ4125 superalloy

DZ4125 superalloy, which processes a high hot cracking sensitivity, is deposited on an as-cast substrate using laser solid forming (LSF) in order to investigate the effect of heat input on the cracking in the deposit and the heat affected zone (HAZ) in the substrate. It is shown that the liquation cracks occurred in LSFed sample with the lower heat input. The propagation extent of the cracks can be reduced with increasing the heat input. The crack-free deposits are achieved when the heat input reaches 150 J/mm. The variation of the residual stress in the LSFed sample with the heat input are discussed based on the micro-indentation analysis. It can be found that the elimination of the cracks with the high heat input can be attributed to the lower temperature gradient and thermal stresses in the LSFed sample. Besides, the backfilling of the liquid melt from the molten pool to the crack is also observed with the high heat input, which is also beneficial to the healing of crack in the HAZ of the molten pool.