Effect of cathode microstructure on arc velocity and erosion rate of cold cathodes in magnetically rotated atmospheric pressure arcs
Bibliographic record
Abstract
Atmospheric pressure arc velocity and arc erosion measurements were performed on thermal sprayed copper cathodes having grain size distributions from submicrometre to a few micrometres in a continuous running arc system. Ultrahigh purity (UHP), 99.99% pure, argon and a mixture of UHP argon with 10% (volumetric) extra dry air were used as plasma forming gases. An external magnetic field of 0.10 T was used to rotate the arc which was operated at a constant power setting of 6 kW (150 A and 40 V). Cathodes having different microstructures were formed using high velocity oxygen fuel (HVOF) spraying and vacuum plasma spraying (VPS) methods with different annealing times. HVOF sprayed cathodes were tested for arc erosion and arc velocity in their as-sprayed state and also after annealing them at 300 and 600 °C for 1 and 8 h durations in an inert argon atmosphere. VPS sprayed coatings were tested as-sprayed. The effect of the initial coating thickness on erosion rates was investigated. Annealing HVOF coatings at 600 °C for 8 h produced near equi-axed grains with a 2–3 µm average size. These coatings showed 60% higher steady state arc velocities and up to 68% lower erosion rates compared with massive copper cathodes having a 20–23 µm average grain size. VPS coatings having a 0.9–1.5 µm average grain size gave up to 70% lower erosion rates when compared with massive copper cathodes. The results show a clear effect of the cathode microstructure on the arc velocity and the erosion rate.
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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 | 0.001 |
| 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 | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".