Novel D022-type precipitate strengthened Mo-enriched cobalt-free maraging steel: Microstructure and mechanical properties

Maraging steels (MAS) are widely used in the aerospace, marine, and defense industries. Given the depleted Co resources and rising international prices, the development of cobalt-free MAS is imperative. In this study, we report a Mo-enriched (4.5-6.0 wt.% Mo) cobalt-free MAS via compositional optimization. The introduction of high-density D0₂₂-type Ni₃Mo/Ni₃(Mo,Ti) precipitates with a superlattice layered structure that maintains coherency with the martensitic matrix has resulted in an alloy with superior mechanical properties. The microstructure and properties of the Mo-enriched MAS have been investigated in homogenized, solid solution, and aged states. The results demonstrate that the proposed alloy exhibits 1.63 GPa tensile strength with 10.2% stain, demonstrating "high-strength and high-ductility" synergy. When compared with conventional MAS (e.g., 18Ni(250) and 18Ni(300) grades), this alloy demonstrates an increase in strength exceeding 200 MPa, achieving a twofold enhancement in tensile ductility, and reducing costs by more than 50%. The alloy exhibits a clearly enhanced cost-performance profile that establishes it as a transformative alternative technology.