Corrosion-resistant steels based on Fe – ~13 % Cr: Heat treatment, corrosion- and wear resistance. Review

Abstract

Martensitic stainless steels with 13 % Cr are widely used in many industries due to their high level of mechanical properties and acceptable corrosion resistance. The paper consolidates information about the guaranteed level of properties and the heat treatment conditions necessary for its implementation. The properties after the treatment proposed by the researchers are compared with the known properties for industrial metal. Dependences of hardness of the hardened steels of 13Cr type with 0.20 – 0.5 % C on austenitization temperature and accompanying changes in the structure were analyzed, the temperatures providing maximum hardening and the temperatures at which the steel ceases to harden were identified. Influence of the austenitization duration, heating and cooling rates on the steels properties is described. The review considers mechanical properties and corrosion resistance after quenching, quenching and tempering in relation to the structural-phase states of steels. It is shown in detail how the type of secondary phases during tempering, their quantity and distribution affect the corrosion resistance of steels with 13 % Cr. It increases with an increase in the heating temperature during austenitization and decreases with an increase in tempering temperature due to precipitation of Cr23C6 carbides and depletion of the matrix in chromium to concentrations below 12 %. The tempering temperature of 500 – 550 °C is recognized as the worst: due to the intense precipitation of carbides, the steel is not passivated, the corrosion rate is maximal. For steels of 20Kh13 type, low tempering quenching (for a combination of high strength, good corrosion resistance and satisfactory ductility) or, more often, high tempering at ~(650 – 700) °C (good ductility, satisfactory corrosion resistance) is recommended. For steels of 40Kh13 type, a temperature of ~700 °C is not recommended due to the increased concentration of carbides and insufficient corrosion resistance. Examples are given of increasing the wear resistance of steels of 40Kh13 type due to surface treatments, from nitriding to laser and plasma surface hardening.