The role of alloying elements in NiAl and Ni3Ti strengthened Co-free maraging steels

Some precipitation hardened steels use a combination of the intermetallic eta-NiAl and beta-Ni3Ti phases to achieve a beneficial combination of ultra-high strength and toughness. The age-hardening in such steels is a complex process that includes the simultaneous formation of precipitates and reverted austenite. The phase constitution and volume fraction of the precipitates strongly depends on the content of the alloying elements, such as Ti, Al, Cr and Mo. By using a step-wise alloy design scheme and high-resolution characterization methods this study seeks to reveal the influence of Ti and Al variations as well as of Cr and Mo on the precipitation hardening and austenite reversion for Co-free maraging steels based on the Fe-12Ni alloy system. It was found that Cr plays a major role in promoting the precipitation of the eta-Ni3Ti phase and simultaneously increases strength and toughness, Ti and Al variations can change the balance between. eta-Ni3Ti and beta-NiAl precipitates and Mo significantly promotes austenite reversion.

Automated summary

Some precipitation hardened steels achieve a beneficial combination of ultra-high strength and toughness by using a combination of the intermetallic eta-NiAl and beta-Ni3Ti phases. The phase composition and volume fraction of the precipitates strongly depend on the content of alloying elements such as Ti, Al, Cr, and Mo. This study aims to reveal the influence of Ti and Al variations, as well as Cr and Mo, on the precipitation hardening and austenite reversion in Co-free maraging steels based on the Fe-12Ni alloy system.