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Microstructural changes as a time temperature indicator in cobalt superalloys and a NiCoCrAlTaY coating
Gas turbines in power generation systems use both nickel and cobalt-based superalloys for vanes, blades, discs and combustion chamber components. Cobalt-based superalloys have the advantage over nickel based superalloys in that they have a higher thermal conductivity and hence a greater thermal shoc...
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| Format: | Default Thesis |
| Published: |
2007
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| Online Access: | https://hdl.handle.net/2134/15182 |
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| Summary: | Gas turbines in power generation systems use both nickel and cobalt-based superalloys for vanes, blades, discs and combustion chamber components. Cobalt-based superalloys have the advantage over nickel based superalloys in that they have a higher thermal conductivity and hence a greater thermal shock resistance, a greater resistance to thermal fatigue and also a better corrosion resistance. However, in some applications coatings have to be applied to such alloys because of their poor oxidation resistance. The creep strength of cobalt-based superalloys depends primarily on solid solution strengthening and the interaction between the hard carbides and alloy defects, such as dislocations and stacking faults. There is a need to develop an understanding of the microstructural changes that occur in cobalt-based superalloys, with both time and temperature, for life prediction, refurbishment and failure investigations... cont'd. |
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