High-throughput characterization of microstructure and corrosion behavior of additively manufactured SS316L-SS431 graded material

Abstract Composition-graded materials could be designed to rapidly establish the structure-property with high-throughput methods. In this study, stainless steel 316L(SS316L) - 431(SS431) graded material with the SS316L content ranging from 0 to 100 wt.% was fabricated by directed energy deposition additive manufacturing. Composition, phase constitution, microstructure and corrosion behavior of the graded material were characterized by laser-induced breakdown spectroscopy (LIBS), micro-beam X-ray diffraction (XRD), scanning electron microscope (SEM) and high-throughput local electrochemical techniques respectively. The results show that the relative amount of γ-Fe phase increases with the increasing SS316L content, leading to a noticeable decline of microhardness from 578 to 205 HV. Accordingly, the dominant microstructure varies from equiaxed dendrites to a mixture of dendritic and cellular structures. As the content of SS316L increases, the reduced carbides at grain boundaries and the increasing compactness of passive film improve the general and pitting corrosion resistance of the material. When the SS316L content is higher than 50 wt.%, the Volta potential and pitting susceptibility are similar to the pure SS316L part, while the microhardness is higher. Such a high-throughput screening process allows one to reliably select the constituents with the presence of SS316L over 50 wt.% as a potential component under the requirement of high corrosion resistance and wear resistance.