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

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 NiFe₁₂]Cr₃, where NiFe₁₂ is a cuboctahedron centered by Ni and surrounded by 12 Fe atoms in FCC structure and Cr serves as glue atoms. A cluster formula NiFe₁₂](Cr₂Ni) with surplus Ni was then determined to ensure the second phase (Ni₃M) precipitation, based on which new multi-component alloys (Ni,Cu)₁₆Fe₁₉₂](Cr₃₂(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 Ni₃M precipitation on the martensite, which enhances the strengths of alloys sharply after ageing treatment. Among them, the aged (Cu₄Ni₁₂)Fe₁₉₂](Cr₃₂(Ni_8.5Mo₂Ti₂Nb_0.5Al₁V₁)) alloy (Fe_74.91Ni_8.82Cr_11.62Mo_1.34Ti_0.67Nb_0.32Al_0.19V_0.36Cu_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.