Corrosion Properties Characterization of 06Cr18Ni10Ti, 08Cr18Ni10Ti Steels and 42CrNiMo Alloy under Conditions Simulating Primary Coolant of Pressurized Water Reactor
V. A. Zuyok, R. A. Rud, M. V. Tretyakov, N. V. Rud, Ya. O. Kushtym, V. V. Shtefan
National Science Center ‘Kharkiv Institute of Physics and Technology’, NAS of Ukraine, 1 Akademichna Str., UA-61108 Kharkiv, Ukraine
Received: 02.01.2023; final version - 15.02.2023. Download: PDF
The article presents an analysis of the corrosion properties of structural materials for primary circuit of light-water reactors. Results of autoclave testing of austenitic stainless steels 06Cr18Ni10Ti, 08Cr18Ni10Ti and chromium–nickel alloy 42CrNiMo in a model environment of primary coolant at a temperature of 350°C and a pressure of 16.5 MPa are presented. Corrosion resistance is estimated by the rate of mass change and the appearance of the samples, the microstructure of the oxide films, and the amount of metal that entered into reaction with the corrosion environment. As established, the samples of the 42CrNiMo alloy, in contrast to the Cr18Ni10Тi steel samples, are oxidized with a mass gain of 9 mg/dm$^2$ for 10 000 hours of testing. The mass index of stainless-steels’ corrosion during the same exposure time almost did not change and is of 0–-2 mg/dm$^2$. The reflectivity of the surface of the samples is decreased slightly, the oxide film is firmly attached to the metal substrate; there is no local corrosion or deposits that indicates the high corrosion resistance of the studied materials. The study of the morphology of the oxide-films’ surface reveals that compact pyramidal-shaped microcrystalline precipitates grow during autoclaving. The corrosion products are chemically removed from the surface of the samples to evaluate the corrosion damage of the studied materials. As shown, after 10 000 hours, the corrosion loss of Cr18Ni10Ti grade steels is of 55 mg/dm$^2$, and for 42CrNiMo alloy, it is 5 mg/dm$^2$. As established, the dissolution coefficient of oxide films, that is the ratio of the mass of the oxide film transferred to the corrosion environment to the total mass of oxide formed during oxidation of the material, is almost zero for the 42CrNiMo alloy, while it is of 30% for stainless steels. This indicates that the application of the 42CrNiMo alloy as a reactor-core structural material will allow eliminating significantly such an undesirable phenomenon as the transfer of corrosion products into the circuit and their further activation. The dependence approximating the corrosion kinetics of stainless steels and Cr–Ni alloy is established. At the initial stages of autoclave exposure (up to 1000 hours), mass loss is described by a power law with an index of power of 0.817 and 0.720 for steels 06Cr18Ni10Ti and 08Cr18Ni10Ti, respectively. Moreover, the indices of power are of 0.347 and 0.352 for longer tests. The experimental results of the mass change of the 42CrNiMo-alloy samples obtained over the entire period of testing are described by one law with an index of power of 0.510. Based on the results of the work, the main conclusion is made that the chrome–nickel alloy 42CrNiMo, in contrast to the stainless steels Cr18Ni10Ti, possess a higher corrosion resistance under model conditions of the light-water reactors’ primary coolant. Oxide films growing on 42CrNiMo surface have almost no tendency to dissolve, in contrast to Cr18Ni10Ti steels with the dissolution coefficient of 30%.
Key words: corrosion, water reactor, oxide, autoclave testing, kinetics of corrosion, 42CrNiMo, Cr18Ni10Ti.
URL: https://mfint.imp.kiev.ua/en/abstract/v45/i04/0481.html
DOI: https://doi.org/10.15407/mfint.45.04.0481
PACS: 28.41.Qb, 28.52.Fa, 68.35.bd, 82.45.Bb, 88.30.Nn
Citation: V. A. Zuyok, R. A. Rud, M. V. Tretyakov, N. V. Rud, Ya. O. Kushtym, and V. V. Shtefan, Corrosion Properties Characterization of 06Cr18Ni10Ti, 08Cr18Ni10Ti Steels and 42CrNiMo Alloy under Conditions Simulating Primary Coolant of Pressurized Water Reactor, Metallofiz. Noveishie Tekhnol., 45, No. 4: 481—501 (2023)