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Aulnoye-Aymeries, France

Thebault F.,Vallourec Research Center France | Bureau-Bayart A.-S.,Vallourec Research Center France | Pineau F.,Vallourec Research Center France | Koschel D.,Vallourec Research Center France | And 3 more authors.
NACE - International Corrosion Conference Series | Year: 2014

NACE TM0177 Method D (DCB) test allows the determination of the critical stress intensity factor KISSC, below which the propagation of a sulfide stress crack in the material is stopped. For a given severity of the sour medium (pH, PH2S, T, [Cl-]...), KISSC is not a material constant since it depends for instance on the testing arm displacement. Recently, the Klimit concept was proposed to circumvent this issue. Klimit is a conservative KISSC value and would be more representative of the material corrosion resistance.A previous communication highlighted that the value of KIapplied is sensitive to the calculation procedure. Consequently, Klimit can be over or underestimated. The present work focused on the influence of experimental parameters on Klimit: the DCB specimen size and the initial crack length. While the influence of those both parameters on KISSC is now well documented, this has not been yet the case for Klimit.Klimit values have been obtained on a C110 casing in NACE TM0177 Solution A for three distinct situations:• with 9.53 mm thick specimens• with 9.53 mm thick specimens that were precracked by fatigue.• with 4.76 mm thick specimens. ©2014 by NACE International. Source

Guedes D.,University of La Rochelle | Guedes D.,Vallourec Research Center France | Oudriss A.,University of La Rochelle | Frappart S.,University of La Rochelle | And 10 more authors.
Scripta Materialia | Year: 2014

A specific dependency of elastic tensile stress on the hydrogen solubility is identified for martensitic steels. The lattice hydrogen concentration under applied stress may be underestimated when predicted by a classical law which associates hydrostatic stress with the partial molar volume of hydrogen. We have explored the impact of elastic distortions on hydrogen solubility from two different sources: internal stresses arising from heterogeneous microstructures and elastic fields around vacancy clusters. Only the latter seems to be in reasonable agreement with our results. © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Source

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