Anisotropic response in mechanical and corrosion properties of hastelloy X fabricated by selective laser melting

Abstract

Mechanical properties and corrosion behaviours of hastelloy X fabricated by selective laser melting (SLM) were investigated and compared with the wrought counterpart, and the anisotropy of the selective laser melted (SLMed) hastelloy X was also clarified in this work. Nano-inclusions (Mo-rich M6C) were widely distributed at the sub-grain boundaries in the SLMed hastelloy X alloy, whereas micron-scale precipitations existed in the wrought counterpart. The grain sizes of the hastelloy X fabricated by SLM on XOZ plane were slenderer than that on XOY plane (equiaxed grains), and the molten pool boundaries widely existed in the SLMed matrix, leading to poor plasticity and the XOY plane was worse due to the cracks perpendicular to the stretching direction. The corrosion resistance for the SLMed matrix was better than the wrought in the less aggressive solution due to the thicker oxide passive film, but the SLMed parts corroded faster in a severe environment once the voids and the molten pool boundaries started to dissolve. The corrosion depth for the SLMed hastelloy X was approximately three times larger than for the wrought and there was little difference on different planes for the SLMed matrix.