Effect of Part Thickness and Build Angle on the Microstructure, Surface Roughness, and Mechanical Properties of Additively Manufactured IN-939

Abstract

Powder bed fusion-laser beam of metals (PBF-LB/M) has attracted significant interest due to the possibility of producing dedicated design features like thin-walled structures, even though their mechanical response and microstructure are not well understood. Hence, thin-walled IN-939 structures of different thicknesses (0.5, 1 and 2 mm) were manufactured at two build angles (90 and 45 deg) by PBF-LB/M. A preferred 〈100〉 crystallographic orientation was found along the build direction in all cases. The crystallographic texture intensity and surface roughness increased as the part thickness decreased for 90 deg and increased for 45 deg build angle. Reduction in wall thickness resulted in a decrease in the tensile properties, e.g., YS decreases by up to 33 pct and UTS decreases by up to 30 pct in comparison with the bulk specimen which had YS of 1051 ± 11 MPa and UTS of 1482 ± 9 MPa. Obtained results indicate that the apparent difference in tensile properties is primarily due to the overestimation of the load-bearing area. Two methods to estimate the accurate tensile properties based on roughness compensation are presented, using of which the corrected tensile performance of the thin-walled specimens was comparable with a standard tensile specimen.