Abstract
The 800°C isothermal and cyclic oxidation of alloys based on Co-7Al-7W (at.%) was examined. Cr, Fe and Si additions were beneficial. Repeated oxide bilayers formed during cycling of non-Cr alloys, which were not protective (>100μm thick). In these layers, the outer was Co3O4 and the inner, a porous Co3O4 and Al2O3 mixture. 10at.% Cr substitution for Co was sufficient to produce a protective, ~1μm thick scale which contained an outer layer of Al2CoO4, a very thin (100nm) middle layer of Cr2O3 and an inner layer of Al2O3. Therefore protective oxide scales are possible in γ/γ', Co-Co3(Al,W) superalloys.
| Original language | English |
|---|---|
| Pages (from-to) | 382-395 |
| Number of pages | 14 |
| Journal | Corrosion Science |
| Volume | 83 |
| DOIs | |
| Publication status | Published - 1 Jan 2014 |
Funding
The authors would like to acknowledge the financial support provided by Rolls-Royce plc. and EPSRC (UK) under the Dorothy Hodgkin Postgraduate Awards scheme (H.-Y.Y.) and by grant EP/H004882/1 (D.D., V.A.V.). Useful conversations with Mark Hardy at Rolls-Royce plc. are also acknowledged. We would also like to thank Richard Sweeney and Ecaterina Ware for their assistance.
Keywords
- superalloys
- STEM
- thermal cycling
- oxidation
- oxidation behaviour
- Co–Al–W superalloys
