Mechanical properties and microstructures of a novel low-carbon high-silicon martensitic steel

Abstract

A novel low-carbon high-silicon martensitic steel, 22SiMnCrNiMo, whose comprehensive mechanical properties approach the 00Ni18Co9Mo4Ti maraging steel, was investigated. Microstructure characterizations revealed that the steel was composed by lath martensite, retained austenite films and ϵ-carbides after different heat treatment processes. And the 22SiMnCrNiMo steel obtained optimal mechanical properties of a yield strength of 1 261 MPa, a tensile strength of 1 548 MPa, an impact toughness of 120 J/cm2, a fracture toughness (KIC) of 94.8 MPa·m1/2 and a threshold value (ΔKth) of 7.1 MPa·m1/2 when the steel was austenitised at 900°C for 1 h followed by water quenched and then tempered at 320°C for 1 h. The 22SiMnCrNiMo steel exhibited excellent mechanical properties similar to those of the 00Ni18Co-9Mo4Ti maraging steel as well as high resistance to fatigue crack initiation and growth.