Additively Manufactured 316L Stainless Steel: Effect of Heat Treatment on Microstructure and Tensile Properties

The microstructure and tensile properties of 316L stainless steel (SS) fabricated using the laser powder directed energy deposition (LP-DED) after various heat treatment (HT) steps such as stress-relief (SR), solution annealing (SA), and hot isostatic pressing (HIP) are characterized. Microstructures before and after HTs are analyzed using both optical and scanning electron microscopy (SEM). Both quasi-static uniaxial tensile and hardness tests are performed to measure mechanical properties. The tensile results indicate that the non-heat treated (NHT) condition possesses higher strengths but lower ductility as compared to the other HT conditions (i.e., SR, SA, HIP, SR+SA, and SR+HIP). By employing the two-step HT conditions (i.e., SR+SA and SR+HIP), no significant changes on tensile properties as compared to the individual single-step HT conditions (i.e., SA or HIP) are observed. The findings suggest that two-step HTs are not required for LP-DED 316L SS unless HIP is needed to minimize volumetric defect contents.