pH estimation at corrosion fatigue crack tip in 13Cr-4Ni martensitic stainless steel
Why this work is in the frame
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Bibliographic record
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.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it