PSI - Issue 68

ScienceDirect Structural Integrity Procedia 00 (2025) 000–000 Structural Integrity Procedia 00 (2025) 000–000 Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect Available online at www.sciencedirect.com ScienceDirect

www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia

Procedia Structural Integrity 68 (2025) 285–291

European Conference on Fracture 2024 pH estimation at corrosion fatigue crack tip in 13Cr-4Ni martensitic stainless steel A. Barabi a* , P.-A. Deschênes b , R. Lacasse b , D. Thibault b , M. Trudeau b , M. Brochu a a Polytechnique Montréal, Department of Mechanical Engineering, 2500, Chemin de Polytechnique, Montréal, Québec, Canada b Institut de Recherche d’Hydro-Québec (IREQ), 1800, Boulevard Lionel-Boulet, Varennes, Québec, Canada Abstract The blades of hydraulic turbines experience repeated loading during operation, promoting initiation and propagation of fatigue cracks in a corrosive environment. To identify the environmental damage mechanism—anodic dissolution or hydrogen embrittlement—potential ( E ) and pH must be measured locally at the crack tip, as values for these parameters measured at the crack tip differ from those measured in the bulk electrolyte. Direct measurement of potential drop ( ∆E=E exterior - E interior ) and pH at the crack tip is, however, challenging. This study focuses on estimating local pH at the fatigue crack tip using thermodynamic analysis combined with ∆E measurements at the crack tip. The methodology was applied to the tip of cracks propagating in a martensitic stainless steel compact tension specimen (CT). ∆E was measured as the crack propagated in a simulated crack environment (deaerated synthetic river water). The potential dropped from 0.075 V SHE in the synthesized river water to -0.09 V SHE in the deaerated synthesized river water. XPS analysis of the corrosion product found on the fracture surface after testing revealed it consisted of Fe₂O₃ and FeCr₂O₄ . Based on a Pourbaix diagram, E = -0.09 V SHE coupled with presence of Fe₂O₃ and FeCr₂O₄ as corrosion products yields a thermodynamically stable solution with a pH ranging from 4.4 to 4.6. © 2025 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 responsibility of ECF24 organizers Keywords: Hydraulic turbine; Low carbon martensitic stainless steel; H embrittlement; pH estimation; Pourbaix diagram European Conference on Fracture 2024 pH estimation at corrosion fatigue crack tip in 13Cr-4Ni martensitic stainless steel A. Barabi a* , P.-A. Deschênes b , R. Lacasse b , D. Thibault b , M. Trudeau b , M. Brochu a a Polytechnique Montréal, Department of Mechanical Engineering, 2500, Chemin de Polytechnique, Montréal, Québec, Canada b Institut de Recherche d’Hydro-Québec (IREQ), 1800, Boulevard Lionel-Boulet, Varennes, Québec, Canada Abstract The blades of hydraulic turbines experience repeated loading during operation, promoting initiation and propagation of fatigue cracks in a corrosive environment. To identify the environmental damage mechanism—anodic dissolution or hydrogen embrittlement—potential ( E ) and pH must be measured locally at the crack tip, as values for these parameters measured at the crack tip differ from those measured in the bulk electrolyte. Direct measurement of potential drop ( ∆E=E exterior - E interior ) and pH at the crack tip is, however, challenging. This study focuses on estimating local pH at the fatigue crack tip using thermodynamic analysis combined with ∆E measurements at the crack tip. The methodology was applied to the tip of cracks propagating in a martensitic stainless steel compact tension specimen (CT). ∆E was measured as the crack propagated in a simulated crack environment (deaerated synthetic river water). The potential dropped from 0.075 V SHE in the synthesized river water to -0.09 V SHE in the deaerated synthesized river water. XPS analysis of the corrosion product found on the fracture surface after testing revealed it consisted of Fe₂O₃ and FeCr₂O₄ . Based on a Pourbaix diagram, E = -0.09 V SHE coupled with presence of Fe₂O₃ and FeCr₂O₄ as corrosion products yields a thermodynamically stable solution with a pH ranging from 4.4 to 4.6. © 2025 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 responsibility of ECF24 organizers Keywords: Hydraulic turbine; Low carbon martensitic stainless steel; H embrittlement; pH estimation; Pourbaix diagram © 2025 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 responsibility of ECF24 organizers

* Corresponding author. E-mail address: aidin.barabi@polymtl.ca * Corresponding author. E-mail address: aidin.barabi@polymtl.ca

2452-3216 © 2025 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 responsibility of ECF24 organizers 2452-3216 © 2025 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 responsibility of ECF24 organizers

2452-3216 © 2025 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 responsibility of ECF24 organizers 10.1016/j.prostr.2025.06.055