Mathematical Modeling of Transport Phenomena in Multi-track and Multi-layer Laser Powder Deposition of Single-Crystal Superalloy

Abstract

The transport phenomena in the multi-track and multi-layer laser powder deposition process of single-crystal superalloy were studied through an improved three-dimensional transient mathematical model. The effect of overlapping ratio on the transport phenomena such as temperature field, molten pool morphology, and thermal gradient distribution was discussed. Laser powder deposition experiments with single-crystal superalloy were conducted to verify the computational results. Results showed that temperature field and molten pool morphology are symmetric in the first track of the first layer, and then become asymmetric in the following tracks and layers due to the overlapping between tracks. The peak temperature in a layer increases quickly in the first three tracks and then gradually tends to steady state. For the same track number, the peak temperature in the second layer is higher than that in the first layer. The overlapping ratio has a predominant influence on the molten pool morphology and the distribution of normal thermal gradient at the solidification interface. With the increase of overlapping ratio, the melting depth of molten pool decreases, while the height of molten pool increases. Good agreement was obtained between the predicted and experimentally results. Under the given processing parameters, continuous epitaxial columnar dendrites were achieved in multi-track and multi-layer laser deposited SX superalloy with the optimized overlapping ratio = 34 pct.