Maraging Steels: Ultra-High Strength Through Age Hardening

Maraging (martensite + ageing) steels are low-carbon (about 0.01 percent C) Fe-Ni (17-19 percent) alloys hardened by Co, Mo, Ti and Al. They are solution-treated to a soft, ductile lath martensite and then age at 480-500 C, where intermetallic precipitates (Ni3Mo, Ni3Ti) raise strength to 1.8-2.4 GPa while keeping excellent toughness and dimensional stability. Floreen (1968) remains the definitive review of their physical metallurgy.

The attraction for tooling and aerospace is machinability in the soft condition and negligible distortion on ageing (no quench). Grades 18Ni (200/250/300/350) are standard; 300-grade (about 1.9 GPa) is common for aircraft landing-gear, rocket-motor cases and high-performance dies. Maraging steel also welds well and can be re-solution-treated after welding.

Caution: maraging grades are costly and best reserved for parts where their combination of strength, toughness and low distortion justifies the price. JLHSteel supplies 18Ni maraging plate and bar with full traceability; we can also advise on nitriding/coating to extend tool life.

References
1. Floreen, S. (1968). The physical metallurgy of maraging steels. Metallurgical Reviews 13(1): 115-128. https://doi.org/10.1179/mtlr.1968.13.1.115
2. Pederson, R., Lindgren, L.-E. (2005). Modelling of mechanical properties for tool and maraging steels. Modelling and Simulation in Materials Science and Engineering 13(4): 509.
3. ASM Handbook, Volume 1 (1990). ASM International.