A finite element model of thermal evolution in laser micro sintering

Laser micro sintering (LMS) is a promising technique for micro-additive manufacturing. During LMS of metallic powder, the material property variation and the heat input energy profile are important to understand physical phenomena involved. This paper presents a finite element temperature distribution profile in LMS of nickel powder on 304 stainless steel substrate. The simulation considered the transition of powder-to-dense sub-model which involves effective thermal conductivity, volumetric enthalpy, and absorptance change; and a moving volumetric Gaussian distribution heat source sub-model. It is found that, for a specified cross section, the mechanism of preheating the nickel powder changes for the heat source from previous laser-irradiated substrate region to molten nickel as the laser beam approaches, while the center of molten pool slice is slightly shifted toward the reverse direction of laser scanning when the laser moves away due to the thermal accumulation effect. Simulated sintered widths showed very good agreement with experimental measurement, and relative prediction errors are below 16 % within the process window.