| EPSRC Reference: |
EP/K016628/1 |
| Title: |
Understanding the memory effect in nickel-based in situ composites |
| Principal Investigator: |
Peel, Dr M |
| Other Investigators: |
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| Project Partners: |
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| Department: |
Mechanical Engineering |
| Organisation: |
University of Bristol |
| Scheme: |
First Grant - Revised 2009 |
| Starts: |
31 October 2013 |
Ends: |
30 January 2015 |
Value (£): |
97,484
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| EPSRC Research Topic Classifications: |
| Materials Characterisation |
Materials testing & eng. |
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| EPSRC Industrial Sector Classifications: |
| Aerospace, Defence and Marine |
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| Panel History: |
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Summary on Grant Application Form |
The reduction of CO2 emissions and improved efficiency is a critical issue with the UK being legally committed to reducing greenhouse gas emissions by 80% by 2050. Turbines for power generation and aircraft propulsion contribute a notable fraction of emissions; it has been estimated that aircraft alone will be contributing 5-15% of anthropomorphic warming by 2050. If emissions are to be reduced these turbines must become more efficient. The most recent 4th generation of superalloys offer the possibility of running safely at higher temperatures, which would significantly boost the turbine's efficiency. However, these alloys are critically dependent on rare, strategic metals like Rhenium with considerable volatility in price and availability - to the point where the use of these new alloys may be restricted. An alternative alloy or material, with excellent high temperature properties but lower dependency on scarce resources, could be significantly more sustainable in the long-run. The materials known as in situ composites are one option.
In situ composites consist of a matrix, normally a conventional nickel superalloy, that contains many aligned micrometre-scale transition metal carbide fibres that are grown as the composite solidifies. The carbide fibres are very stable and strong, even at the extreme temperatures in a gas turbine, and reinforce the matrix allowing it to operate at higher temperatures than normal. Importantly, this can be accomplished without the addition of Rhenium. However, the deformation behaviour of in situ composites is difficult to understand and we currently have little ability to predict their long-term reaction to use in a turbine. A particularly interesting phenomenon thought to be exhibited by in situ composites is the 'memory effect'. In most cases, a high temperature component, such as a turbine blade, must be removed from service and replaced when it has deformed beyond a critical amount. Damaged blades made of in situ composites may only require a short heat treatment to recover their original life span and dimensions. Unfortunately, the memory effect has only been reported on a few occasions and at the moment little is known about how it occurs or the conditions needed to initiate it. If this phenomenon can be proved to occur and the underlying mechanisms understood, it would substantially increase the life span of turbine components. Used components could be returned to active service, at a greatly reduced expenditure of energy, and so greatly improving the sustainability of the industry.
The behaviour of in situ composites is thought to depend heavily on the interaction between the superalloy matrix and the carbide fibres providing the reinforcement, in particular the transfer of load to the fibres as deformation progresses. This project will use novel measurement techniques, such as synchrotron X-ray diffraction, to perform rapid experiments to directly determine the stresses and strains in the material as it is undergoing deformation and experiencing the memory effect. X-ray methods provide a direct measure of the strain experienced by each phase and so reveal how load is passed to the fibres, how the matrix is deforming and even the onset of fibre fracture. This data will be complemented by advanced microstructural analysis methods such as electron backscattered diffraction, which can quantify the state of the material after deformation. Combining these advanced methods will allow us to determine the underlying physics governing these novel materials. This data will be used to adapt a set of creep models in order to predict the behaviour of in situ composites. This data will be vital in developing the next generation of turbine materials.
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Key Findings |
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This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk
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Potential use in non-academic contexts |
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This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk
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Impacts |
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| Description |
This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk |
| Summary |
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| Date Materialised |
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Sectors submitted by the Researcher |
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This information can now be found on Gateway to Research (GtR) http://gtr.rcuk.ac.uk
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| Project URL: |
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| Further Information: |
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| Organisation Website: |
http://www.bris.ac.uk |