Maraging steels are ultra-high-strength alloys whose microstructure and mechanical properties are predominantly determined by aging temperature. This study systematically compares the aging response (at 450, 500, 550 °C) of Co-containing and Co-free Mo-modified grades. Results reveal that Co significantly enhances precipitation kinetics and refines precipitate distribution, while effectively suppressing the formation of reverted austenite. This alters the strength–toughness balance, with Co-containing alloys achieving higher strength and Co-free alloys exhibiting superior ductility. Mechanical testing identified 500 °C as the optimum aging temperature. Strengthening mechanism analysis confirmed that Co promotes a synergistic combination of matrix and precipitation strengthening. This work elucidates Co’s governing role in precipitation and phase transformation, providing a foundation for designing high-performance maraging steels.
Wang et al. (Sat,) studied this question.