Nonstationary thermokinetic model of surface laser scanning

This paper presents a thermophysical model of laser beam scanning of the surface of a two-layer plate, whose top layer melts and shrinks due to changes in porosity, and whose bottom layer (substrate) does not melt. The dependences of the heat capacity, thermal conductivity, and reflection coefficient on porosity are taken into account. Heat loss is due to both radiation and convection. Results are presented showing that the process is nonstationary throughout the scan. It is shown that the complex thermal cycles and inhomogeneous temperature field are directly related to inhomogeneous shrinkage, leading to the surface topography typical of selective laser melting processes.