Temperature variation and mass transport simulations of invar alloy during continuous-wave laser melting deposition

Continuous-wave laser melting deposition (LMD) offers several advantages, such as higher cooling rate, finer microstructures and improved mechanical properties over traditional processing technology. The fluid flow in the molten pool affects the solute distribution and the microstructure morphology when invar alloy mould is repaired with laser melting deposition. However, the effects of laser on the molten pool motion, thermal field and microstructure of invar alloy are not distinct. In this work, a three-dimensional model utilizing the volume of fluid method was developed to simulate the transient molten pool motion, heat transfer and fluid flow for the laser melting deposition process. The interaction among powder, laser and molten pool in LMD process was comprehensively considered in the model. The laser melting deposition with Nano-WC powder particles as a dispersoid was investigated. The simulated molten pool geometry was compared with experimental results. Moreover, temperature variation, fluid flow and their influence on the microstructure were analyzed. It is concluded that a significant Marangoni flow is observed with the highest velocity in the middle of the molten pool but lower in the surface and bottom of the molten pool. The lower velocity of fluid flow results in an element accumulation in the bottom of the molten pool. This study provides a referenced value for revealing the flow mechanism of molten pool in the LMD process of invar alloy.