Raising the Properties of Steel 30KhGSA by Creating a Mixed Martensitic-Austenitic Structure

The structure and properties of steel 30KhGSA are studied after hardening by the quenching and partitioning (Q&P) process and, for comparison, by the standard modes of quenching and tempering. Metallographic and fractographic analyses and impact bending tests of the steel are performed. Kinetic diagrams of fatigue fracture are plotted, and the stress intensity factor ∆ K and the rate of growth of fatigue crack v are computed. It is shown that the Q&P treatment yields a heterogeneous martensitic structure with interlayers of ductile retained austenite, which raises the impact toughness of the steel by a factor of 1.5 – 2 and the resistance to fatigue crack propagation by a factor of 1.5 as compared to the same characteristics after the traditional quenching and tempering. The strength of the steel remains virtually unchanged. The Q&P treatment may be recommended for raising the structural strength of heavily loaded machine parts.