Numerical analysis of thermal stress evolution of multiple paths and positions of laser-based directed energy deposition

Residual stress in laser-based directed energy deposition technology (LDED) is the main barrier which hinders its extensive application seriously. However, the difficulty in measuring residual stress during the deposition process and the unclear mechanism of its spatial multi-path evolution have limited the control of residual stress in the LDED manufacturing process. Therefore, in this study, a three-dimensional (3D) transient uncoupled thermo-elastic–plastic model is carried through to examine the thermal history and multi-path, multi-node, multi-directional residual stress distribution in IN718 LDED process. The numerical simulation temperature and residual stress results are validated by the experimental measurement data. It is discovered that the temperature field distribution of the multi-track is no longer symmetric along the laser scanning direction and two thermal cycles are experienced at different locations on each path. As the laser power and scanning speed increase, the rate of variation of the maximum temperature decreases. The residual stresses were mainly concentrated on the deposition track, and the maximum residual stresses increased with the increase in laser power and the decrease in scanning speed. The residual stresses in the multi-track LDED varied greatly in different paths and locations, with higher residual stresses in the X–Y plane at the junction of adjacent passes in the perpendicular deposition direction, a slow rise in the deposition direction, and a gradual decrease in the depth direction. It provides operation process parameters optimization choice with guidance to control or reduce residual stress in LDED manufacturing.