Heat Treatment Design for IN718 by Laser Metal Deposition with High Deposition Rates — Modeling, Simulation and Experiments

Abstract

Laser metal deposited processed Ni-based superalloy IN718 is characterized by elemental micro-segregation, anisotropy and Laves phases due to the rapid solidification and therefore needs homogenization heat treatment to achieve comparable properties of wrought alloys. In this paper, we report simulation based methodology to design heat treatment IN718 in a laser metal deposition process using Thermo-calc. Initially, the finite element modeling simulates the laser melt pool to compute the solidification rate (G) and temperature gradient(R). Then, the primary dendrite arm spacing are computed through Kurz-fisher [20] and Trivedi [14] modeling integrated with FEM solver. Later a DICTRA homogenization model based on the Primary Dendrite Arm Spacing (PDAS) input values computes the homogenization heat treatment time and temperature. The simulated time scales are verified for two different experiments with contrast laser parameters and are found to be in good agreement confirmed with the results from scanning electron microscopy (SEM). Finally a methodology for integrating the process parameter with the heat treatment design is developed, and a heat treatment map for IN718 is generated that can be integrated with a FEM solver first time in Laser metal deposition process.