Numerical Simulation of the Temperature Distribution and Solid-Phase Evolution in the LENS~TM Process

摘要

A three-dimensional finite element model was developed and applied to analyze the temperature and phase evolution in deposited stainless steel 410 (SS410) during the Laser Engineered Net Shaping (LENS~(TM)) rapid fabrication process. The effect of solid phase transformations is taken into account by using temperature and phase dependent material properties and the continuous cooling transformation (CCT) diagram. The laser beam is modeled as a Gaussian distribution of heat flux from a moving heat source with conical shape. The laser power is optimized in order to achieve a pre-defined molten pool size for each layer. It is found that approximately 5% decrease of the laser power for each pass is required to obtain a steady molten pool size. The temperature distribution and cooling rate surrounding the molten pool are predicted and compared with experiments. Based upon the predicted thermal cycles and cooling rate, the phase transformations and their effects on the hardness are discussed.