Microstructure and Solidification Cracking Analysis of Dissimilar Pulsed Laser Welded Hastelloy X to 347 Stainless Steel Using Phase-Field Models

A phase-field model is utilized to associate the solidification behavior of dendrites to the microscopic characteristics of the weld and to characterize the microstructure evolution in dissimilar pulsed laser welded Hastelloy X to 347 stainless steel alloy. The simulations reveal that the morphology of the dendrites during rapid solidification of the molten zone is affected by a melt flow and dilution level. The effect of melt flow as a result of Marangoni convection is modeled by Boussinesq approximation to adjust the concentration field around a developing dendrite, modifying its growth morphologies. The enhancement of hot cracking resistance is studied by adjusting the microstructure morphology through the possibility of the backfilling of the melt for the most efficient dendrite spacing, which was evaluated by correlation of the heat conduction problem and the phase-field model. Besides, the laser offset was estimated by finding the optimal chemical composition of the weld zone in the ternary Fe-Nieq-Creq system that affects the microstructure predicted by the phase-field model. The segregation of nanoparticle compounds analyzed by TEM in interdendritic regions is possible for primary dendrite spacing higher than 3 μ m and consequently the solidification cracking susceptibility is increased. Graphic Abstract