Mechanical Properties and Microstructures of a Novel Low carbon High-silicon Martensitic Steel

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 epsilon-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/cm(2), a fracture toughness (K-IC) of 94.8 MPa.m(1/2) and a threshold value (Delta K-th) of 7.1 MPa.m(1/2) when the steel was austenitised at 900 degrees C for 1 h followed by water quenched and then tempered at 320 degrees 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.