Mathematical Modeling of Crystal Growth and Microstructure Formation in Multi-layer and Multi-track Laser Powder Deposition of Single-crystal Superalloy

A self-consistent three-dimensional mathematical model was developed to predict the crystal growth and microstructure formation in multi-layer and multi-tracklaser powder deposition of single-crystal superalloy. Laser powder deposition experiments with nickel-based single-crystal superalloy were conducted to verify the computational results. The results indicated that the overlapping ratio was the key parameter to ensurethe continuity and consistency of the epitaxial columnar dendrite growth. Both small and large overlapping ratios lead to residual stray grain region of the previously deposited layer. Scanning with alternating X and Y direction method produces better result with the continuous columnar dendrite growth compared to that of the one direction scanning method. With proper deposition parameters and the alternating scanning method, the epitaxial growth of columnar dendrite microstructure can be achieved in a multi-track and multi-layer deposit.