Computational Modeling and Experimental Validation of Microstructure Development in Nickel-Base Superalloys Processed through Scanning Laser Epitaxy (SLE)

This paper focuses on computational modeling and experimental validation of microstructure evolution in Scanning Laser Epitaxy (SLE), an additive manufacturing technology aimed at the repair and production of turbine engine hot-section components made of for superalloys. A coupled thermal and fluid flow model is developed to simulate the melt pool created by the scanning laser’s heat source. The detailed effects of natural and Marangoni convection on the flow field are studied and the results are analyzed in terms of the temperature gradient, the vorticity parameter, the melt pool dimensions and the mushy region extent. The geometrical parameters and the temperature gradient of the melt pool then are used to estimate the resulting solidification microstructure in alloy CMSX-4 for any given position of the beam. The critical parameter values for columnar-to-equiaxed and the oriented-to-misoriented transitions are identified. The microstructural predictions show excellent agreement with experimental metallography and process observations. This work is sponsored by the US Office of Naval Research through grant N00014-11-1-0670.