Composition design of superhigh strength maraging stainless steels using a cluster model

Abstract

The composition characteristics of maraging stainless steels were studied in the present work investigation using a cluster-plus-glue-atom model. The least solubility limit of high-temperature austenite to form martensite in basic Fe–Ni–Cr corresponds to the cluster formula [NiFe 12 ]Cr 3 , where NiFe 12 is a cuboctahedron centered by Ni and surrounded by 12 Fe atoms in FCC structure and Cr serves as glue atoms. A cluster formula [NiFe 12 ](Cr 2 Ni) with surplus Ni was then determined to ensure the second phase (Ni 3 M) precipitation, based on which new multi-component alloys [(Ni,Cu) 16 Fe 192 ](Cr 32 (Ni,Mo,Ti,Nb,Al,V) 16 ) were designed. These alloys were prepared by copper mould suction casting method, then solid-solution treated at 1273 K for 1 h followed by water-quenching, and finally aged at 783 K for 3 h. The experimental results showed that the multi-element alloying results in Ni 3 M precipitation on the martensite, which enhances the strengths of alloys sharply after ageing treatment. Among them, the aged [(Cu 4 Ni 12 )Fe 192 ](Cr 32 (Ni 8.5 Mo 2 Ti 2 Nb 0.5 Al 1 V 1 )) alloy (Fe 74.91 Ni 8.82 Cr 11.62 Mo 1.34 Ti 0.67 Nb 0.32 Al 0.19 V 0.36 Cu 1.78 wt%) has higher tensile strengths with YS =1456 MPa and UTS =1494 MPa. It also exhibits good corrosion-resistance in 3.5 wt% NaCl solution.