Sensitization, desensitization, and carbide evolution of Alloy 800H made by laser powder bed fusion

Abstract

Additively manufactured (AM) Alloy 800H made by laser powder bed fusion (L-PBF) exhibited a greater degree of sensitization than wrought 800H, leading to both intergranular and intercellular corrosion. Dislocation cellular boundaries showed mild Cr depletion as compared to high-angle grain boundaries (HAGBs). Boundary misorientation of < 5⁰ was found mitigating sensitization. Carbide growth in AM 800H was controlled by particle net growth at the early stage and Ostwald ripening at the later stage. Cellular structure was confirmed producing faster elemental diffusion than bulk diffusion and random dislocation structures by cold rolling, and leading more rapid carbide growth, chromium depletion, and desensitization on HAGBs. Sensitization along cellular boundaries is not the main cause of intercellular corrosion in the sensitized AM Alloy 800H.