Thermal Resistance of Steels with Increased Strength Properties for Pressure Vessels of Advanced VVER Reactors of Various Designs
The paper considers the results of structural studies and mechanical tests after a long-term thermal exposure of laboratory heats of the metallurgically improved 15Kh2NMFA steel and steel with an increased content of nickel viewed as materials for the pressure vessels of advanced VVER-type reactors of various designs. It has been shown that, both for the improved 15Kh2NMFA steel and the high-nickel steel, there are no signs of grain boundary embrittlement after a thermal treatment that provokes embrittlement. This is explained by the extremely low grain boundary segregation of phosphorus in the initial state caused by a high degree of the structure dispersion as well as by rather a low content of impurities. Besides, no changes have been found in the yield strength value for the improved 15Kh2NMFA steel, which agrees with the structure investigation results. For the high-nickel steel, a tendency has been revealed towards a minor yield strength decrease by 5 to 10- and a regular reduction in the critical brittle temperature. A decrease in the mechanical performance has been caused by a relatively low temperature of the high-nickel steel temper and, accordingly, by the potential occurrence of the structure after-temper processes during long-term thermal exposure, as evidenced by results of an X-ray diffraction analysis. Despite the after-temper processes in the high-nickel steel in the course of the long-term heat exposure, the basic strengthening carbide phases remain stable. Due to this, the yield strength value remains at a relatively high level that exceeds the values for the currently employed VVER-type vessel steels, even in the case of a thermal exposure much in excess of the expected operating conditions of advanced VVER reactors. And the critical brittle temperature decrease in the course of the heat exposure just contributes to an increase in the steel resistance to brittle fracture in the process of service.
- Alekseev P.N. Directions for the Development of the Nuclear Power System. Innovatika i Ekspertiza. 2016, iss. 3(18), pp. 67-80. Available at: https://elibrary.ru/download/elibrary_29032662_68651559.pdf (accessed Feb. 01, 2023) (in Russian).
- Markov S.I., Dub V.S., Lebedev A.G., Kuleshova E.A., Balikoev A.G., Makarycheva E.V., Tolstykh D.S., Frolov A.S., Krikun E.V. Advanced Reactor Vessel Steels for Reactors with Supercritical Coolant Parameters. Russ. Metall. 2016, no. 9, pp. 803-811; DOI: https://doi.org/10.1134/S003602951609010X .
- Pratomo S.B., Oktadinata H., Widodo T.W. Effect of Nickel Additions on Microstructure Evolution and Mechanical Properties of Low-Alloy Cr-Mo Cast Steel. IOP Conf. Ser. Mater. Sci. Eng. 2019, v. 541, 012050, pp. 1-8; DOI: https://doi.org/10.1088/1757-899X/541/1/012050 .
- Shtrombakh Y.I. Gurovich B.A., Kuleshova E.A., Frolov A.S., Fedotova S.V., Zhurko D.A., Krikun E.V. Effect of Ni Content on Thermal and Radiation Resistance of VVER RPV Steel. J. Nucl. Mater. 2015, v. 461, pp. 292-300; DOI: https://doi.org/10.1016/j.jnucmat.2015.02.023 .
- Kuleshova E.A., Zhuchkov G.M., Fedotova S.V., Maltsev D.A., Frolov A.S., Fedotov I.V. Precipitation Kinetics of Radiation-Induced Ni-Mn-Si Phases in VVER-1000 Reactor Pressure Vessel Steels Under Low and High Flux Irradiation. J. Nucl. Mater. 2021, v. 553, 153091, pp. 1-11; DOI: https://doi.org/10.1016/j.jnucmat.2021.153091 .
- Lee B.S., Kim M.C., Yoon J.H., Hong J.H. Characterization of High Strength and High Toughness Ni-Mo-Cr Low Alloy Steels for Nuclear Application. Int. J. Press. Vessel. Pip. 2010, v. 87, no. 1, pp. 74-80; DOI: https://doi.org/10.1016/j.ijpvp.2009.11.001 .
- BalandinYu.F., Gorynin I.V., ZvezdinYu.I., Markov V.G. NPP Structural Materials. Moscow. Enegoatomizdat Publ., 1984, 280 p. (in Russian).
- Kuleshova E.A., Fedotov I.V., Maltsev D.A., Potekhin A.A., Bubyakin S.A., Isaenkova M.G., Krymskaya O.A., Minushkin R.A. Structural Features Ensuring the Increase of Service Characteristics of High-Nickel Steels for Pressure Vessels of Prospective Energy-Generation Reactors. Int. J. Press. Vessel. Pip. 2022, v. 200, 104845, pp. 1-13; DOI: https://doi.org/10.1016/J.IJPVP.2022.104845 .
- Kuleshova E.A., Fedotov I.V., Maltsev D.A., Frolov A.S., Stepanov N.V., Safonov D.V. The Role of Nickel in the Formation of a Structure that Provides Improved Service Characteristics of Reactor Structural Materials. Izvestiya vuzov. Yadernaya Energetika. 2022, no. 3, pp. 120-133; DOI: https://doi.org/10.26583/npe.2022.3.11 (in Russian).
- Holloman J.H., Jaffe J.H. Time-Temperatures Relations in Tempering Steel. Trans. Am. Inst. Min. Met. Eng. 1945, v. 162, pp. 223-249.
- Kameda J., Nishiyama Y. Combined Effects of Phosphorus Segregation and Partial Intergranular Fracture on the Ductile-Brittle Transition Temperature in Structural Alloy Steels. Mater. Sci. Eng. A. 2011, v. 528, no. 10-11, pp. 3705-713; DOI: https://doi.org/10.1016/j.msea.2011.01.018 .
- Shtrombakh Y.I., Gurovich B.A., Kuleshova E.A., Maltsev D.A., Fedotova S.V., Chernobaeva A.A. Thermal Ageing Mechanisms of VVER-1000 Reactor Pressure Vessel Steels. J. Nucl. Mater. 2014, v. 452, no. 1-3, pp. 348-358; DOI: https://doi.org/10.1016/j.jnucmat.2014.05.059 .
- Naudin C., Frund J.M., Pineau A. Intergranular Fracture Stress and Phosphorus Grain Boundary Segregation of a Mn-Ni-Mo Steel. Scr. Mater. 1999, v. 40, no. 9, pp. 1013-1019; DOI: https://doi.org/10.1016/S1359-6462(99)00069-X .
- Fedotova S.V., Kuleshova E.A., Maltsev D.A., Saltykov M.A. Complex Study of Grain Boundary Segregation in Long-Term Irradiated Reactor Pressure Vessel Steels. J. Nucl. Mater., 2019, v. 528, 151865, pp. 1-8; DOI: https://doi.org/10.1016/j.jnucmat.2019.151865 .
- Saltykov S.A. Stereometric Metallography. Ed. 3, rev. Moscow. Metallurgiya Publ., 1970, 376 p. (in Russian).
- Ungбr T., Tichy G., Gubicza J., Hellmig R.J. Correlation Between Subgrains and Coherently Scattering Domains. Powder Diffr. 2005, v. 20, no. 4, pp. 366-375; DOI: https://doi.org/10.1154/1.2135313 .
- Ungбr T. Microstructural Parameters from X-Ray Diffraction Peak Broadening. Scr. Mater., 2004, v. 51, no. 8, pp. 777-781; DOI: https://doi.org/10.1016/j.scriptamat.2004.05.007 .
- Akhavan Tabatabae B., Ashrafizadeh F., Hassanli A.M. Influence of Retained Austenite on the Mechanical Properties of Low Carbon Martensitic Stainless Steel Castings. ISIJ International. 2011. v. 51, no. 3, pp. 471-475; DOI: https://doi.org/10.2355/isijinternational.51.471 .
- Markov S.I. Metallurgical Foundations for the Production of Blanks for Highly Reliable Elements of Energy and Pipeline Systems. Dr. Sci. (Engineering) Diss. Moscow. OAO NPO «CNIITMASH» Publ., 2012, 83 p. (in Russian).
- Physical Materials Science: Textbook for Universities: in 8 v. / Ed. by B.A. Kalin. Ed. 3, rev. / Volume 1. Solid State Physics / G.N. Elmanov, A.G. Zaluzhny, V.I. Skrytny, E.A. Smirnov, Yu.A. Perlovich, V.N. Yalcev. Ed. 3, rev. Moscow. MEPhI Publ., 2021, 764 p. ISBN 978-5-7262-2725-2 (in Russian).
Link for citing the article: Kuleshova E.A., Fedotov I.V., Maltsev D.A., Isaenkova M.G., Krymskaya O.A., Minushkin R.A. Thermal Resistance of Steels with Increased Strength Properties for Pressure Vessels of Advanced VVER Reactors of Various Designs. Izvestiya vuzov. Yadernaya Energetika. 2023, no. 2, pp. 93-106; DOI: https://doi.org/10.26583/npe.2023.2.08 (in Russian).