Impact of build direction on microstructure and high-temperature mechanical properties of SLM-fabricated 316L stainless steel

Abstract

Additive manufacturing (AM) has gained significant attention over the last decade. Among the various factors influencing final product quality, the build direction notably affects mechanical properties. This study utilized selective laser melting (SLM) to fabricate 316L stainless steel in three directions: 45°, 90°, and 180°. These building directions were analyzed at room temperature and elevated temperatures to examine the building directions’ effects on the microstructure and tensile properties. Additionally, the impact toughness and microhardness of 316L stainless steel in different building directions were evaluated. SLM 316L stainless steel manufactures equiaxial and columnar cell structures that result in higher mechanical properties over conventionally produced 316L. The horizontal specimens exhibited a superior synergy of strength among the three building directions at room temperature, with yield stresses of 582 MPa and ultimate tensile stresses of 742 MPa. In contrast, the vertical specimen had the lowest yield stress of 474 MPa and ultimate tensile stress of 640 MPa and showed remarkably low ductility. At an elevated 400 °C temperature, strength values in all build directions decreased. Horizontal specimens have the highest mechanical properties at elevated temperatures, with a yield stress of 372 MPa and an ultimate tensile stress of 457 MPa. Overall, the horizontal and 45°-built specimens showed a better combination of mechanical properties than the vertical specimens in both temperatures. The vertical specimen had an elongation of 10.5%, which was less than half the elongation of the other building directions.