Remelting Model and Cracking Criterion for Vacuum Arc Remelting of Superalloys: Taking IN718 as an Example

To enhance the quality of vacuum arc remelting (VAR) ingots in enterprises, a remelting model and cracking criterion was developed based on simulation and a series of designed experiments to predict the segregation behavior, shrinkage cavity, thermal stress, and cracking tendency of VAR ingot. The remelting model was established by MeltFlow-VAR and Abaqus software. As MeltFlow-VAR cannot calculate the stress, through the secondary development program, the thermal stress of VAR ingot was calculated by introducing the temperature field of VAR process into Abaqus. This model was verified by longitudinal dissection of a 406 kg IN718 alloy VAR ingot. The simulated evolution of molten pool, shrinkage cavity, freckle formation probability and secondary dendrite arm spacing (SDAS) align consistently with the ingot microstructure and experimental results. Combined with thermal stress, the alloy strength at different temperature during cooling and solidification, and failure criterion, a crack criterion was constructed to predict the cracking tendency. Calculating the complete solidification time and cracking tendency of the VAR ingot after melting allows for the determination of the safe demolding time without cracks. This method can be used to explore the effect of different melting parameters, optimize VAR process and improve the quality of VAR production.