Investigation of Oxidation Performance of Co-Cr-Fe-Ni based High Entropy Alloys in Supercritical-CO2 Environment
Bibliographic record
Abstract
This work presents the first oxidation studies of Co-Cr-Fe-Ni-based high entropy alloys (HEAs) in supercritical-CO2 (sCO2) environment.These materials are being evaluated as an alternative to commercial Ni-based superalloys for construction of select components of sCO2 power cycles.The alloys investigated in this research include CoCrFeMnNi, Al0.5CoCrFeMnNi1.5, Al0.5CoCrFeNi1.5,(CoCrFeMnNi)Si0.01,and CoCrFe0.5MnNi1.5 specifically designed to study the impact of Mn, Al, Si and Fe on the oxidation behaviour.The HEAs were characterized through scanning electron microscopy (SEM), energy-dispersive Xray spectroscopy (EDS), X-ray diffraction before and after exposure to sCO2.The samples were tested inside a high pressure sCO2 corrosion test rig located at Natural Resources Canada's, capable of mimicking the operating conditions of indirectly-fired sCO2 power cycles.The oxidation behaviour was evaluated by comparing experimentally obtained mass gain data and the characterized oxide formations.The pre-exposure results show that Al0.5CoCrFeMnNi1.5 and Al0.5CoCrFeNi1.5 compositions form γ/γ' microstructure, desirable for high strength applications, while the exposure to sCO2 at elevated temperatures (500-700°C) and pressure (20 MPa) causes formation of ordered B2 NiAl phases dispersed within the matrix.Al0.5CoCrFeNi1.5 is the only composition that forms detectable protective Cr2O3 after 300 hours at 500°C/20MPa, as well as after 600 hours at 700°C/MPa.The other four compositions were shown to form a porous unprotective MnO oxide layer.Additionally, the results indicate that similar to conventional alloy systems, the oxidation of HEAs increases with temperature, however, Al0.5CoCrFeNi1.5 exhibited nearly the same mass gain at both temperatures after 300 and 600 hours.Lastly, the results suggest that Al0.5CoCrFeNi1.5 composition has the potential to outperform commercial superalloys in sCO2 applications.
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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".