PSI - Issue 52

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Jiri Dvorak et al. / Procedia Structural Integrity 52 (2024) 259–266 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 9. Changes in the occurrence and ratio of Traces measured by AE for individual stages of creep.

4. Conclusions Creep behaviour of high chromium feritic P92 steel was studied under simultaneous monitoring using the AE method. The analyses of creep data indicate that the creep deformation and fracture are controlled by the same mechanisms where creep process is controlled by climb of dislocations. Microstructure after creep testing at 600°C contains M 23 C 6 carbides which are predominantly located along grain boundaries and small MX precipitates inside lath boundaries and subgrains. Examination of fracture surface revealed transgranular ductile failure resulting from coalescence of cavities. Creep damage formation was localized using new AE signal processing algorithms based on artificial neural networks. Continuous monitoring of this formation during creep exposition has shown that it is possible to catch in time initiation and propagation of defects in pressurized pipes. Acknowledgements The authors acknowledge the financial support for this work provided by the Technology Agency of the Czech Republic through Grant No. TK03020089 - THÉTA References Abe, F., Nakazawa, S., 1992. The effect of tungsten on creep Behavior of Tempered Martensitic 9Cr Steels. Metall Mater Trans A 23, 3025 – 3034. Abe, F., Nakazawa, S., Araki, H., Noda, T., 1992. The role of microstructural instability on creep behavior of a martensitic 9Cr-2W steel. Metallurgical Transactions A 23, 469 – 477. Beere, W., 1981. Theoretical Treatment of Creep Cavity Growth and Nucleation, in: “ Cavities and Cracks in Creep and Fatigue ”. In: Gittus,J. (Ed.) Applied Science Publishers, London, UK. Cadek, J., 1988. Creep in metallic materials. Elsevier, Amsterdam; New York. Ennis, P.J., Zielinska-Lipiec, A., Wachter, O., Czyrska-Filemonowitz, A., 1997. Microstructural Stability and Creep Rupture strength of the Martensitic Steel P92 for Advanced Power Plant. Acta Materialia 45, 4901-4907. Evans, H.E., 1984. Mechanisms of Creep Fracture , Elsevier Applied Science, Barking, UK. Grosse, C.U., Ohtsu, M., Aggelis, D.G., Shiotani, T., 2021. Acoustic Emission Testing: Basics for Research – Applications in Engineering. Springer Nature.