Influence of recoil pressure, mushy zone flow resistance and reflectivity on melt pool shape in laser powder bed fusion simulation

Abstract

Melt pool dimensions (depth: D and width: W) are strongly correlated with defects generated in laser powder bed fusion. The melt pool dimensions have been evaluated by CFD simulation including solid–liquid–gas phase change and laser multiple reflection. Such a multi-physics simulation requires a large number of parameters. Preliminary simulations for parameter identification require a lot of time and effort. The parameter sensitivity to the melt pool dimensions is important; however, the systematic evaluations have hardly been found in the literature. In this study, we performed systematic parametric evaluation for three parameters related to recoil pressure, flow resistance in solid–liquid mushy zone and Fresnel laser reflection. As a result, the D values increased with increasing recoil pressure, but the W values did not. The flow resistance force influenced the velocities in the mushy zone but not the melt pool dimensions. The D increased with increasing reflectivity, but the W did not. The melt pool dimensions varying recoil pressure, flow resistance force and reflectivity were all inconsistent with the experimental melt pool dimensions. In order to agree with the experimental melt pool dimensions, the problems to be solved were discussed by comparing the previous studies.

Keywords

• Laser powder bed fusion
• Multi-physics CFD simulation
• Recoil pressure
• Mushy zone flow resistance
• Fresnel laser reflection model
• Melt pool shape