Root cause of embrittlement of in-service exposed high pressure steam pipeline

0570444 - ÚFM 2024 RIV NL eng C - Conference Paper (international conference)
Ohanková, M. - Čmakal, J. - Junek, M. - Kvapilová, Marie - Dvořák, Jiří - Sklenička, Václav
Root cause of embrittlement of in-service exposed high pressure steam pipeline.
Procedia Structural Integrity. Vol. 43. Amsterdam: Elsevier B. V., 2023 - (Pokluda, J.; Šandera, P.), s. 300-305. ISSN 2452-3216.
[MSMF10 - International Conference on Materials Structure and Micromechanics of Fracture /10./. Brno (CZ), 12.09.2022-14.09.2022]
R&D Projects: GA TA ČR(CZ) TK03020089
Institutional support: RVO:68081723
Keywords : Steam pipeline * embrittlement * microstructure * mechanical properties * heat treatment * low-alloyed steel
OECD category: Materials engineering

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.
Permanent Link: https://hdl.handle.net/11104/0341898