Assessing the effect of scan strategies on the structure-property relationship in electron beam powder bed fusion processed 316L stainless steel
Prithwish Tarafder, Jinghao Xu, Anton Wiberg, Johan Moverare
Abstract
• Different spot and line melting strategies were investigated in EB-PBF process. • Scan strategies influenced thermal history and resulting microstructure of 316L. • Microstructural analyses were performed using OM, SEM, and EBSD. • Room temperature tensile test showed feasibility of using adopted scan strategies. • Localized microstructural variation was realized in exemplary industrial component. Different electron beam path patterns realized in eight varying scanning strategies were adopted in an electron beam powder bed fusion machine to understand the effect of scan patterns on the microstructure and mechanical properties of 316L austenitic stainless steel. Results showed that variation in localized microstructure is principally determined by the beam path length and the extent of melting-remelting cycles. Sporadic dislocation sub-structures were observed in scan strategies where thermal conditions were more turbulent than the reference raster scan, eventually leading to a different mechanical response despite their lower measured densities. Average yield strength and ultimate tensile strength surpassed the conventionally produced and subsequently annealed 316L; and were very close to the standards set forward for nuclear applications. This therefore opens up the possibility of using different scan strategies in an electron beam powder bed fusion system that can exploit the scan path design freedom and achieve localized microstructural and property differences. A proof-of-concept scaled-down version of an industrial component was fabricated with varying scan patterns at different areas and mechanically tested to showcase the feasibility of the presented approach.