CREEP DAMAGE OF LOW-ALLOY STEELS AFTER LONG-TERM EXPOSURE AND ITS EVALUATION BY REPLICA METHOD

1 KUBOŇ Zdeněk
Co-authors:
1 KOSŇOVSKÁ Jana 1 KANDER Ladislav
Institution:
1 Material and Metallurgical Research (Ltd.), Pohraniční 693/31, Vítkovice,703 00 Ostrava, Czech republic, EU, zdenek.kubon@mmvyzkum.cz
Conference:
27th International Conference on Metallurgy and Materials, Hotel Voronez I, Brno, Czech Republic, EU, May 23rd - 25th 2018
Proceedings:
Proceedings 27th International Conference on Metallurgy and Materials
Pages:
749-754
ISBN:
978-80-87294-84-0
ISSN:
2694-9296
Published:
24th October 2018
Proceedings of the conference were published in Web of Science and Scopus.
Metrics:
12 views / 6 downloads
Abstract

The intended operation time prolongation of the key components of fossil-fuelled power plants working in the creep conditions over 200,000 or even 250,000 hours (far beyond their original design lifetime) must be accompanied by thorough and extensive monitoring of the current material state and particularly creep damage. The extent of cavitation damage is routinely tested in-situ by using replica method and its quantification is based on a practice stated in VGB-TW 507, NORDTEST NT TR 170 or NORDTEST NT TR 302 that further develop the original Neubauer's classification. Although the evaluation of cavitation damage based on the measurement of the number of cavities and/or creep micro-cracks is a routine activity, what is still in question is the depth of the damaged area and the corresponding material properties through the wall thickness.Mutual correspondence between the creep damage evaluation performed in accordance with NORDTEST NT TR 302 and VGB TW 507 was carried out in a pipe bend made of a low-alloy 0.5Cr-0.5Mo-0.3V steel which was creep exposed at 525-540 °C for more than 225,000 hours and the relation between creep damage at the outer surface of the pipe bend (as a typical result of replica testing) and mechanical properties of the whole pipe bend were discussed in the paper with reference to the residual life assessment.

Keywords: 0.5Cr-0.5Mo-0.3V steel, long-term creep exposure, cavitation, creep damage, residual life.
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