Model of laser energy absorption adjusted to optical measurements with effective use in finite element simulation of selective laser melting

The presented research work has developed an adjusted analytical equation that can accurately describe energy absorption in powder-substrate geometry observed in Selective Laser Melting. Without high demand of computing capacity, this equation can be used in Finite Element evaluation of temperature profile that explains well experimental observations. The equation was developed from a solution of one-dimensional Radiation Transfer Equation. The adjustment is made referring to measured absorption data extended using a carefully set Ray Tracing model. The diffuse mode of radiation propagation was found to be more accurate for atomized powder. This agrees with observed particle surfaces that are not mirror-like to qualify for specular reflection. Simulated cooling curve helped to understand the influence of scanning a given layer on final microstructure of underlying layers in 316L SS. By studying different combinations of laser power and scanning speed; data for prediction of “under-heated” “well-heated” and “excessively-heated” regions were generated. These data revealed that, in a certain range of laser power, the concept of energy density metric can still work for fixed hatch and layer thickness; if an “off-set power” is introduced.