Microstructure and high temperature tensile properties of narrow gap braze joint between X-40 and IN738
Bibliographic record
Abstract
In the braze repair of gas turbine components, substituting the parent metal with dissimilar metals can improve the mechanical properties of the refurbished parts. In this study, the microstructure and high temperature tensile properties of brazed joints made of X-40 (the parent metal) and IN738 (the substitute metal), were evaluated in the narrow gap as brazed and heat treated conditions. The resulting joint contained primary γ-Ni phase, discrete refractory element rich carbides/carboborides and eutectic phases. The carbides and eutectic phases exhibited Vickers hardness values several times higher than those of IN738 and γ-Ni phase particles. The high temperature yield strength of the as brazed joints was also greater than that of the X-40 base metal, but the ductility was significantly lower. The fracture surfaces revealed that cracking occurred in both intergranular (among the γ-Ni grains) and transgranular modes. Crack initiation was found to be associated with discrete carbides/carboborides and eutectic phases. It was observed that post-braze heat treatment at 950°C for 120 h improved the high temperature tensile ductility due to a reduction of carbides and eutectic phases in the brazed joint. Increasing the heat treatment time reduced the size and the amount of carbides and eutectic phases and contributed to an increase in transgranular fracture. However, extending the heat treatment time up to 840 h reduced the ductility due to oxidation damage in the braze joint.
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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".