Microstructure evolution and mechanical properties of maraging steel 300 fabricated by cold spraying additive manufacturing

Abstract: Additive manufacturing (AM) of maraging steel has attracted increasing attention due to its outstanding mechanical properties. As a recently-emerged AM method, the solid-state cold spray has been widely used to fabricate the metallic components. In this work, the maraging steel 300 (MS300) was fabricated by cold spray additive manufacturing and following solution-aging treatment. Analyses based on X-ray computed tomography (XCT) and optical microscope (OM) show densified microstructure with minimum porosity of 0.159 %. Phase analysis through XRD and EBSD exhibits that as-fabricated samples exhibit a well-retained phase composition compared with feedstock material, and the solution-aging lead to a highly martensitized microstructure in MS300. EBSD analysis shows the low pattern quality and ultrafine grain structure of as-fabricated samples indicating the formation of dynamic recrystallization during the CS deposition. Tensile tests show that through the cohesive diffusion and precipitation-strengthening, the solution-aging treatment can lead to a significantly improved tensile properties (ultimate tensile strength and elongation) with the fracture morphology featured by extensive dimples. The wear resistance of CS MS300 was also significantly improved through the precipitation-hardening despite the coarsened microstructure. As a summary, this study demonstrates cold spray as a promising AM method to fabricate high-performance grade 300 maraging steels.