PSI - Issue 17

Jaromír Janoušek et al. / Procedia Structural Integrity 17 (2019) 440–447 Jaromír Janoušek / Structural Integrity Procedia 00 (2019) 000 – 000

447

8

on the grain boundaries of the Nickel coupon exposed for 5 days at 350 °C to the 6 times more oxidizing environment with respect to the Ni/NiO transition. All CERT curves at 350 °C exhibited oscillations of load, which are typical for dynamic strain ageing. Tests with the slower extension rate achieved higher strengths. The maximum stress at the minimum cross-section of the tapered tensile specimen was higher in comparison with published values. For the room temperature test the maximum stress was 612 MPa (table UTS value is 567 MPa). For the specimen tested at 350 °C the maximum stress was 458 MPa (table UTS value is 421 MPa). Both CERT curves measured in the H 2 -steam environments showed greater elongation. Plastic deformation of varying extents appeared as slip bands emerging from the surface. Several ductile cracks initiated from the slip bands. The FEGSEM observation of the failed specimens revealed typical ductile fracture dimples.

Acknowledgements

This work has been undertaken within the SUSEN Project (established in the framework of the European Regional Development Fund (ERDF) in the project CZ.1.05/2.1.00/03.0108 and of the European Strategy Forum on Research Infrastructures (ESFRI) in the project CZ.02.1.01/0.0/0.0/15_008/0000293, which is financially supported by the Ministry of Education, Youth and Sports - project LM2015093 Infrastructure SUSEN. The support of Horizon 2020 MEACTOS GA No. 755151 is also acknowledged.

References

Raja, V. S. and Shoji, T., 2011. Stress corrosion cracking, Theory and practice, Woodhead Publishing Limited Shoji, T., 2003. Progress in the Mechanistic Understanding of BWR SCC and Its Implication to the Prediction of SCC Growth Behavior in Plants, Proc. 11th Int. Conf. Environmental Degradation of Materials in Nuclear Systems, Stevenson, pp. 588-599. Couvant, T., Moulart, P., Legras, L., Bordes, P., Capelle, J., Rouillon, Y., Balon, T., 2006. PWSCC of austenitic stainless steels of heaters of pressurizers, 6th Symposium Fontevraud: SFEN. Turnbull, A., Mingard, K., Lord, J. D., Roebuck, B., Tice, D.R., Mottershead, K.J., Fairweather, N.D., Bradbury, A.K., 2011. Sensitivity of stress corrosion cracking of stainless steel to surface machining and grinding procedure, Corrosion Science 53, pp. 3398 – 3415. Couvant, T., Legras, L., Herbelin, A., Musienko, A., Ilevbare, G., Delafosse, D., Cailletaud, G., Hickling, J., 2009. Development of Understanding of the Interaction between Localized Deformation and SCC of Austenitic Stainless Steels Exposed to Primary PWR Environment, 14th Int. Conf. on Environmental Degradation of Materials in Nuclear Power Systems, Virginia Beach. Persaud, S. Y., Korinek, A., Huang, J., Botton, G. A., Newman, R. C., 2014. Internal oxidation of Alloy 600 exposed to hydrogenated steam and the beneficial effects of thermal treatment, Corrosion Science 86, 108 – 122. Economy, G., Jacko, R. J., Pement, F. W., 1987. Igscc Behavior of Alloy 600 Steam-Generator T ubing in Water or Steam Tests above 360 C,” Corrosion, vol. 43, no. 12, pp. 727 – 73. Yu, J., Xue, L J., Zhao, Z. J., Chi, G. X., Parkins, R.N., 1989. Determination of Stress Corrosion Crack Initiation Stress and Crack Velocities using Slowly Strained Tapered Specimens, Fatigue Fracture of Engineering Materials and Structures 12, pp. 481-493. Berger, S., Kilian, R., Ritter, S., Ehrnstén, U., Bosch, R.-W., Perosanz Lopez, F.-J., 2016. Mitigation of crack initiation in LWRs (MICRIN+), Paper No. 65952, Eurocorr, Monpellier. Janoušek, J., Scenini, F., Volpe, L., Hojná, A., Trojan, T., 2018. Instrumentation for SCC testing in low pressure superheated hydrogen steam environments, IOP Conference Series: Materials Science and Engineering, Volume 461, Issue 1. Scenini, F., Newman, R.C., Cottis, R.A., Jacko, R.J., 2005. Alloy 600 oxidation studies related to PWSCC, Proceedings of the 12th International Symposium on Environmental Degradation of Materials in Nuclear Power System - Water Reactors, Minerals, Metals and Materials Society/AIME, pp.891 – 902.