Abstract
The results are presented on the oxidation behaviour of two chromia-forming steels, over the temperature range 800°C to 900°C, regions of premature localised breakaway oxidation were observed. SiO2 formation along emergent grain boundaries encapsulated smaller grains, acting as diffusion barriers to the replenishment of chromium from deeper in the alloy. Rapid depletion of chromium from these isolated grains continued with increasing time until the concentration was insufficient to maintain a protective Cr2O3 resulting in the localised chemical failure and formation of breakaway oxides. A finite difference model was used to demonstrate the effect of SiO2 formation. It was also found that the low concentration of silicon restricted the encapsulation process to only the smaller grains at the surface and protective oxidation was re-established underneath at the alloy surface. The predicted lifetime of components with wall thicknesses of 2 mm was calculated to be in excess of 30 years.
Original language | English |
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Pages (from-to) | 318-330 |
Number of pages | 13 |
Journal | Materials at High Temperatures |
Volume | 40 |
Issue number | 4 |
Early online date | 25 Feb 2023 |
DOIs | |
Publication status | Published - 31 Dec 2023 |
Keywords
- diffusionally isolated grains
- Oxidation
- steels
ASJC Scopus subject areas
- Ceramics and Composites
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering
- Metals and Alloys
- Materials Chemistry