Calibration of Laser Penetration Depth and Absorptivity in Finite Element Method Based Modeling of Powder Bed Fusion Melt Pools

Abstract

A systematic parametric study was conducted using thermal finite element method simulations in order to calibrate the laser penetration depth and absorptivity as a function of the laser power and scan speed for single tracks of Alloy 718 processed by laser powder bed fusion. A methodology was developed to calibrate both laser penetration depth and absorptivity using an algorithm proposed. Calibrated laser penetration depths and absorptivities captured experimentally observed variations of the melt pool depth and width with the laser power and scan speed, and showed strong correlations with a modified energy density, which is the laser power normalized by a square root of the scan speed (W/(m/s)1/2). The result indicated that the laser penetration depth and absorptivity heavily influence the determination of the melt pool depth and width, respectively. Variations of calibrated laser penetration depths and absorptivities with the laser power and scan speed reasonably depicted physical phenomena related with how incident laser beam interacts with the melt pool under different input energy densities, and were in quantitative agreement with those calculated from an analytical model and observed from the experiment.