Building rate effect on microstructure and high temperature mechanical properties of Austenitic 316L stainless steel manufactured by laser directed energy deposition

Improving the build rate of additive manufacturing (AM) processes has been of great industrial interest to enhance productivity, reduce costs and increase efficiency. Increasing the build rate in AM is typically achieved by optimizing the process parameters. However, the impacts of these process parameters changes on the resulting microstructure and high temperature mechanical performance in AM is not yet understood. The present study highlights that increasing the build rate, achieved by enlarging the laser beam diameter and laser power while maintaining the energy density, influences the microstructure, tensile properties, and creep behaviour of 316L stainless steel processed using laser directed energy deposition (LDED). Results demonstrate that nearly fully dense LDED samples were achieved at various deposition conditions. Remarkably, LDED samples produced with an increase build rate exhibited superior tensile properties at high temperature and enhanced creep performance. Regarding anisotropy, a lower build rate with optimized process parameters promoted the formation of a finer and more anisotropic microstructure, resulting in significant anisotropy in creep behaviour. In contrast, a higher build rate yielded a uniform microstructure, leading to uniform creep behaviour across different orientations. This study highlights the potential of LDED for achieving superior and uniform high temperature mechanical performance through an increased build rate.