Microstructure and mechanical behavior of PH 13–8Mo martensitic stainless steel fabricated by wire arc additive manufacturing

Abstract

Wire arc additive manufacturing (WAAM) was applied to fabricate precipitation hardened (PH) 13–8Mo martensitic stainless steel parts for applications in injection molding equipment, aerospace components, and marine. The microstructural features, microhardness evaluation, and room temperature tensile properties of the as-printed parts have been comprehensively investigated at different locations and orientations. The experimental results showed that the predominant microstructure of the WAAM fabricated PH 13–8Mo stainless steel part mainly consists of vermicular and lathy remnant δ-ferrite embedded in a low-carbon fine martensitic matrix in addition to a small fraction of retained austenite. The content of both retained austenite and remnant δ-ferrite reduced through the building direction of the WAAM fabricated wall, causing a gradual increase of microhardness and ultimate tensile strength values from the bottom to the top of the component. Moreover, the measured tensile strength and ductility in horizontal and vertical directions of the wall revealed anisotropic mechanical properties associated with the columnar growth of primary δ-ferrite grains structure formed during the solidification of the material, creating a strong cubic texture along the building direction. The present study, for the first time, revealed successful implementation of WAAM technology to fabricate PH 13–8Mo stainless steel parts with comparable hardness and tensile strength with respect to other fabrication methods.