Laser direct deposition of AISI H13 tool steel powder with numerical modeling of solid phase transformation, hardness, and residual stresses

Abstract

This study is concerned with the systematic study on the laser direct deposition of AISI H13 tool steel powder on H13 substrates to determine and investigate the hardness and residual stresses resulting from the laser deposition process. In this paper, numerical models are presented to predict three-dimensional solid phase transformation, material hardness, and residual stresses produced by the laser direct deposition process with multi-track and multi-layer capabilities. The simulated laser deposition track is based on the predicted temperature and geometry from a free-surface-tracking laser deposition model. The predictive modeling results are validated by experiments in terms of tempering patterns, hardness field measurements, and XRD residual stress measurements. Predicted results show the variation of stresses and hardness into the depth and along the surface of the workpiece, providing a reasonable agreement with measured values. It is found that the heat-affected zone with high phase fractions of martensite result in strong compressive stresses, but the tempering effect due to multi-track laser deposition can somewhat alieviate the compressive stress. It is also found that the ultimate tensile strength of laser deposited H13 steel is 15% to 30% higher than published values for commercial H13.