Modeling and Characterization of Microstructure Evolution in Single-Crystal Superalloys Processed through Scanning Laser Epitaxy

This paper focuses on microstructure evolution in single-crystal alloys processed through scanning laser epitaxy (SLE); a metal powder-bed based additive manufacturing technology aimed at the creation of equiaxed, directionally-solidified or single-crystal structures in nickel-base superalloys. Galvanometer-controlled movements of the laser and high-resolution raster scanning result in improved control over the melting and solidification processes in SLE. Characterization of microstructural evolution as a function of the complex process physics in SLE is essential for process development, control and optimization. In this paper an ANSYS CFX based transient flow-thermal model has been developed to simulate microstructure characteristics for single-crystal superalloys such as CMSX-4 and René N5. Geometrical parameters and melt pool properties are used to estimate the resulting solidification microstructure. Microstructural predictions are compared to experimental metallography and reasonably good agreement is achieved.