Heat-affected zone cracking in new 718-type superalloy VDM alloy 780: Effect of solution heat treatments and comparison with alloy 718
Bibliographic record
Abstract
• Liquation cracking in VDM 780 occurs via supersolidus and MC carbide liquation. • Heat treatment at 1050 °C yields the lowest liquation cracking susceptibility. • Grain coarsening outweighs boron segregation in increasing cracking propensity. • Severe grain coarsening occurs at 1150 °C; 1050 °C promotes strong boron segregation. • VDM 780 exhibits superior liquation cracking resistance over Alloy 718. The weld heat-affected zone liquation cracking susceptibility of new 718-type superalloy VDM Alloy 780 was studied under various pre-weld solution heat treatment (SHT) conditions using the Varestraint test and compared with Alloy 718. Similar to Alloy 718, liquation cracking in VDM Alloy 780 occurs by constitutional liquation of NbC and supersolidus melting. Among the conditions studied, the 1050 °C/0.5 h SHT exhibits the lowest cracking propensity, followed by 1090 °C/2h, 1150 °C/4h, and 1150 °C/4h + 1050 °C/0.5 h. Within this SHT range, grain coarsening and equilibrium segregation of boron at the grain boundaries are identified as major factors deteriorating the cracking resistance in VDM Alloy 780, with grain coarsening being the more dominant factor. When both factors coexist, the cracking susceptibility further increases. The most significant grain coarsening takes place at 1150 °C, while the strongest boron segregation occurs after the 1050 °C SHT. In its optimal SHT condition that resists cracking (1050 °C/0.5 h), VDM Alloy 780 exhibits superior liquation cracking resistance to Alloy 718 despite having a six times coarser grain size, which appears to be due to its substantially higher fraction of coincident site lattice boundaries (25 % higher).
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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) | 0.002 | 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".