Laser directed energy deposition of AISI 316L stainless steel: The effect of build direction on mechanical properties in as-built and heat-treated conditions

Abstract

The purpose of this study was to evaluate the effect of build direction on the mechanical properties of AISI 316L stainless steel using the Laser Directed Energy Deposition (L-DED) process, in the as-built and heat-treated conditions. The test specimens were manufactured in vertical and horizontal directions for tensile and impact tests. In addition, analysis test specimens cube-shaped were manufactured for microstructural and microhardness evaluation. The microstructure in the as-built condition showed a combination of cellular, equiaxial dendritic, cellular dendritic and columnar dendritic, while the microstructure in the heat-treated condition showed a homogeneous characteristic, composed by differently sized grains. The microhardness evaluation in the heat-treated condition presented a reduction of 26.52% compared to the as-build condition. The ultimate tensile strength of horizontal test specimens in the as-built condition was 4.86% higher than the heat-treated condition, whereas the ultimate tensile strength of vertical test specimens in the as-built condition was 5.55% higher than the heat-treated condition. The impact resistance of horizontal test specimens in the heat-treated condition was 12.36% higher than the as-built condition, whereas the impact resistance of vertical test specimens in the heat-treated condition was 18.92% higher than the as-built condition. Briefly, the build direction directly affects the mechanical properties of components manufactured through the L-DED process, and it is possible to improve certain mechanical properties, such as ductility and toughness, through heat treatment.