Experimental and Modeling Studies of Creep Performance of Modified 9Cr-1Mo Steels with or without Oxidation-Resistant Coating
Bibliographic record
Abstract
This thesis presents experimental and modeling studies of creep performance of modified 9Cr-1Mo steel with and without an oxidation-resistant coating.A deformation-mechanism-based truestress (DMTS) creep model is proposed for predicting creep rate and creep life of modified 9Cr-1Mo steels.The DMTS model considers three well-recognized deformation mechanisms: dislocation glide, dislocation climb, and grain boundary sliding.Constant-load creep testing is conducted on modified 9Cr-1Mo steel in forged form, F91 (9Cr-1Mo-V-Nb).The creep performance of three types of F91 coupons, pristine, coated, and aged coupons is studied.The creep data obtained in the present study and those reported from the literature are used to validate the DMTS model.Four major achievements are obtained from this study.(i) The creep rate behavior of nine modified 9Cr-1Mo steels in various product forms including tubes, pipes, plates, and forging is systematically characterized in terms of power-laws representing the aboveidentified deformation mechanisms; (ii) The creep strain-time behavior of the pristine and coated F91 steel is analyzed to verify the basic DMTS model and the modified DMTS model with consideration of oxidation, showing excellent agreement with the experimental observations; (iii) The effect of microstructural evolution is studied using aged F91 coupons, showing that Lave phase formation associated with grain boundary sliding is mostly responsible for the increased creep rate and shortening of creep life as compared to the pristine material; (iv) Last but not the least, long-term creep lives (>10 4 hours) of modified Grade 91steels are predicted using the modified DMTS model, showing pronounced improvement over the basic model, indicating that oxidation effect is significant in long-time creep, whereas direct extrapolation from short-term
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".