PSI - Issue 43

Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect StructuralIntegrity Procedia 00 (2022) 000 – 000 Available online at www.sciencedirect.com ScienceDirect StructuralIntegrity Procedia 00 (2022) 000 – 000

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ScienceDirect

Procedia Structural Integrity 43 (2023) 300–305

© 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under the responsibility of MSMF10 organizers. © 20 23 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under the responsibility of MSMF10 organizers. Abstract A segment of tub cut off rom the high p essure steam pipeline was subjected to routine basic material tests, which resulted in very ow impact energy of the pipe material (low-alloyed Cr steel). A part of the segment (a d a comparative non- perated sampl ) as then subjected to detailed mechanical tests (including creep), metallograp ic investigations and fractographic nalyses with an aim to deter ine root ause of the mbrittlement. The results showed that grain boundaries of exposed st el are covered by particles of prim ry nd second ry cementite. Howev r, matrix is weakened more, therefore a fract re of creep, tensile and i pact specimens is always transgranular and the cleavage f cets are limited to grain size, if pr sent. Thus, the cause of embrittlement was determined not by a rapid ageing, but by an unsuitable initial heat treatment of the pipe material. © 20 23 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under the responsibility of MSMF10 organizers. 10th International Conference on Materials Structure and Micromechanics of Fracture Root cause of embrittlement of in-service exposed high pressure steam pipeline Marie Ohanková a, *, Josef Čmakal a , Michal Junek a , Marie Kvapilová b , Jiří Dvořák b , Václav Sklenička b a UJP PRAHA a.s., Nad Kamínkou 1345, 156 00 Prague - Zbraslav, Czech Republic b Institute of Physics of Materials, Czech Academy of Sciences, Žižkova 513/22, 616 00 Brno, Czech R epublic Abstract A segment of tube cut off from the high pressure steam pipeline was subjected to routine basic material tests, which resulted in very low impact energy of the pipe material (low-alloyed Cr steel). A part of the segment (and a comparative non-operated sample) was then subjected to detailed mechanical tests (including creep), metallographic investigations and fractographic analyses with an aim to determine a root cause of the embrittlement. The results showed that grain boundaries of exposed steel are covered by particles of primary and secondary cementite. However, a matrix is weakened more, therefore a fracture of creep, tensile and impact specimens is always transgranular and the cleavage facets are limited to grain size, if present. Thus, the cause of embrittlement was determined not by a rapid ageing, but by an unsuitable initial heat treatment of the pipe material. 10th International Conference on Materials Structure and Micromechanics of Fracture Root cause of embrittlement of in-service exposed high pressure steam pipeline Marie Ohanková a, *, Josef Čmakal a , Michal Junek a , Marie Kvapilová b , Jiří Dvořák b , Václav Sklenička b a UJP PRAHA a.s., Nad Kamínkou 1345, 156 00 Prague - Zbraslav, Czech Republic b Institute of Physics of Materials, Czech Academy of Sciences, Žižkova 513/22, 616 00 Brno, Czech R epublic

Keywords: Steam pipeline; embrittlement; microstructure; mechanical properties; heat treatment; low-alloyed steel Keywords: Steam pipeline; embrittlement; microstructure; mechanical properties; heat treatment; low-alloyed steel

1. Introduction During the scheduled shutdown after about 7 years of operation, a straight part with a weld was cut off from the tube of high pressure steam pipeline at the point, where the new technology had to be connected. The steam pipeline 1. Introduction During the scheduled shutdow after about 7 years of operation, a straig t part with a weld was cut off from th tube of high pressure steam pipeline at the point, where the new technology had to be connected. The steam pipeline

* Marie Ohanková. Tel.: +420 -227-180-326. E-mail address: ohankova@ujp.cz * Marie Ohanková. Tel.: +420 -227-180-326. E-mail address: ohankova@ujp.cz

2452-3216 © 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under the responsibility of MSMF10 organizers. 2452-3216 © 2023 The Authors. Published by Elsevier B.V. This is an ope access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under the responsibility of MSMF10 organizers.

2452-3216 © 2023 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under the responsibility of MSMF10 organizers. 10.1016/j.prostr.2022.12.275