Influence of high-temperature thermomechanical treatment with deformation at 900 °C on structural-phase state and microhardness of EK-181 steel

Abstract

The microstructure of 12% chromium ferritic-martensitic steel EK-181 formed during thermomechanical treatment with deformation at 900 °C is investigated. It is shown that this treatment leads to a refinement of the parameters of the steel microstructure and an increase in the dislocation density and the magnitude of microdistortions of the crystal lattice, compared to the state after quenching. Plastic deformation at 900 °C followed by tempering allows reducing the average sizes of the prior-austenite grains by 2 times, the width of martensite laths by almost 4 times, and the particles of the carbide phase M₂₃C₆ by 2 times, compared to the state after traditional heat treatment. In this case, the density of dislocations and the degree of lattice microdistortions increase by 2 times. The microhardness of EK-181 steel is also studied. It is shown that plastic deformation at 900 °C leads to a 15% increase in the steel microhardness in the quenched state and by 10% after additional tempering.