Microstructure and mechanical properties of a novel Cu-reinforced maraging steel for wire arc additive manufacturing

Abstract In this study, a novel Cu-reinforced SHER120-G maraging steel was developed for the wire arc additive manufacturing (WAAM) process. The microstructural evolution, mechanical properties, and Ɛ-copper particle-strengthening mechanisms of the samples were investigated. The content of δ-ferrite and austenite increases with the increase of deposition height due to the unique thermal cycle characteristics of WAAM process. High-resolution transmission electron microscopy (HRTEM) images of the age hardened specimens clearly exhibit that there is a small amount of fine Ɛ-copper particles in the as-deposited sample due to the transient ageing effect. After direct ageing, a uniform and dense distribution of Ɛ-copper particles with the size about 6 nm formed in the martensite matrix. The yield strength and microhardness were significantly increased owing to the Orowan bypass mechanism and strain strengthening. The ultimate tensile strength, elongation and impact toughness reach 1221 MPa, 11.76% and 63 J, respectively. Additionally, improvements in the elongation and impact toughness characteristics were caused by the finer lath martensite, the disappearance of δ-ferrite, and the formation of higher content of reversed austenite during ageing.