Computational modeling and experimental validation of melting and solidification in equiaxed superalloys processed through scanning laser epitaxy

This paper focuses on simulation-based optimization of the Scanning Laser Epitaxy (SLE) process applied to gas turbine hot-section components made of nickel-base superalloys. SLE creates equiaxed, directionally-solidified and single-crystal microstructures from superalloy powders melted onto like-chemistry substrates using a fast scanning, high power laser beam. In this paper, a transient coupled flow-thermal approach is implemented to accurately simulate the melting and solidification process in SLE. The laser movement is modeled as a Gaussian moving heat source, and the thermophysical properties of the alloys are adjusted based on the thermal field. Simulations for different superalloys such as IN100, René 80 and MAR-M247 are performed and the instantaneous melt pool characteristics are recorded. Comparisons of the simulations with experimental results show reasonably good agreement for the melt depth. Feedback control is implemented, and demonstrated to produce superior quality SLE deposits.