Build size and infill effects on SS316L microstructure in laser wire directed energy deposition

The directional thermal profile inherent to metal additive manufacturing processes influences the microstructure and mechanical properties. Build geometry and size introduce further complexity in microstructural evolution. This study explores how sample size and printing strategy affect the microstructure and properties of LW-DED of stainless steel 316 L. Two sample sizes and two printing strategies were employed. EBSD data revealed a dominant orientation along the scan direction. Smaller samples experience greater heat accumulation, which promotes epitaxial growth in the XY plane and along the build direction, leading to coarser grains. The infill strategy and sample size combined influence the crystallographic orientation along the build direction in different ways. In the larger samples, the introduction of interlayer rotation intensifies and promotes the orientation along the build direction. In the smaller samples, the absence of interlayer rotation stabilizes epitaxial growth across successive layers, which strengthens grain continuity along the build direction and intensifies the orientation. Smaller samples exhibit larger PDAS compared to the larger samples, reflecting a slower cooling rate. This coarser dendritic structure leads to consistently lower hardness values in the smaller samples. The printing strategy affects solidification orientation, altering grain and thereby influencing both microstructure and mechanical response.