Research on the evolution mechanism of solidified structure during laser cladding IN718 alloy

Abstract

• An improved CA-FE model is used to explore the evolution of the microstructure. • A CET model is established to quantitatively study the solidification parameters. • The relationship between solidification parameters and microstructure is explored. • The mechanism of grain growth during the solidification is revealed. • Increasing the laser power and scanning speed will promote the CET process. In the direct energy deposition (DED) process of IN718, the microstructure significantly affects the properties of the workpieces, but the evolution mechanism of the microstructure has not been systematically studied, so it is valuable to understand the solidification process in the molten pool. In this study, a simplified temperature field model is established and the cellular automata (CA) model is used to explore the evolution of the microstructure during DED, which can effectively simulate the microstructures of IN718 with different process parameters. Then a columnar to equiaxed crystal transition (CET) model is established to quantitatively reveal the relationship between solidification parameters and microstructures throughout the solidification process, and the mechanism of grain growth during the solidification of molten pool is further explored, finding that increasing the laser power and scanning speed will promote the CET process with the equiaxed crystal content increasing from 6.18% to 33.8%. This study can be used to simulate the solidification process of IN718 during DED and obtain the required microstructures by optimizing the processing parameters.