Structure, Phase Composition, and Mechanical Properties of a High Strength Steel with Transition Carbide η-Fe2C

• Published in: Physics of metals and metallography Vol. 124; no. 12; pp. 1319 - 1332
• Main Authors: Borisova, Yu. I., Mishnev, R. V., Tkachev, E. S., Kniaziuk, T. V., Gaidar, S. M., Kaibyshev, R. O.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01.12.2023; Springer Nature B.V
• Subjects: Carbides; Cementite; Chemistry and Materials Science; Ductile fracture; Ductile-brittle transition; Heat treating; High strength steel; High strength steels; Impact strength; Intergranular fracture; Intergranular precipitation; Martensite; Materials Science; Mechanical properties; Metallic Materials; Phase composition; Quenching and tempering; Strength and Plasticity; Tempering; Yield strength; Yield stress; tempering; high strength steel; microstructure; impact toughness; ductile–brittle transition; mechanical properties; carbide
• ISSN: 0031-918X; 1555-6190
• DOI: 10.1134/S0031918X23602445

— The effects of quenching and tempering on the structure, phase composition, and mechanical properties of the Fe–0.34C high strength steel with 1.77 wt % Si are studied. The tempering at temperatures up to 500°C barely has an effect on the structural characteristics of packet martensite formed during quenching. The precipitation of intermediate (transition) η-carbide particles at tempering temperatures in the range of 200–400°C leads to increases in the yield strength to 1490 MPa and in the impact toughness to 35 J/cm 2 . The determined temperature of the ductile–brittle transition of the steel tempered at 200°C is about –50°C. A decrease in the impact toughness and a decrease in the proportion of ductile fracture with a decrease in the test temperature are accompanied by a transition from transgranular to intergranular fracture. The precipitation of cementite particles along the boundaries of the laths and blocks is observed after tempering at 500°C. This leads to a decrease in the yield strength, while the impact toughness of the steel remains unchanged.