Improvements in Gas Turbine Performance via Novel Plasma Spray Coatings offering Protection against Ingested Species

This project will involve extensive collaboration between three teams of researchers, two in the UK and one in India. The expertise and facilities of the three teams are highly complementary and together constitute a uniquely appropriate set of resources to tackle the challenges of the proposed programme. In addition, three industrial partners, all with highly relevant technical background and interests, will be actively engaged in the research. There will be extensive exchanges of samples and personnel between the partners, designed to disseminate technical expertise and facilitate the experimental programme. The work will concern an important area of manufacturing development, namely improvement of the performance of protective ceramic coatings in gas turbine engines (for both propulsion and power generation). In particular, the proposed research will lead to improved understanding of the mechanisms by which ingested species (such as sand, ash, salt etc) can cause degradation and debonding of these coatings, and also to evaluation of some promising counter-measures (which have not previously been investigated for this purpose). The coatings will be produced by plasma spraying, an advanced manufacturing technique used by several of the partners, with novel variants of the process also being available within the partnership. Experimental work will also encompass the use of a small jet engine to investigate the adhesion of ingested particulate on substrates within the turbine, complemented by extensive modelling studies.

Beneficiaries
1) Suppliers of Coatings and Coating Technology. There are several UK-based firms involved in supply of (thick) ceramic coatings of the type used for thermal barrier function (and also abradable coatings for gas flow control). Prominent among these is Monitor Coatings, which is a partner in the proposed programme. They would clearly be well-placed to take advantage of information emerging from the project.

2) Suppliers of Gas Turbine Engines. AMT is a small, but rapidly growing, firm involved in the manufacture of small gas turbine aeroengines. The collaborative work planned with them should give valuable insights into the factors affecting adhesion of ingested particulate within aeroengines. Furthermore, outcomes of the programme will be of considerable benefit to various other firms involved in manufacture, supply and maintenance of gas turbines being used for various purposes.

3) Airlines and Air Travellers. Improved understanding of the effects involved should contribute to improved confidence concerning engine toleration limits. This confidence would also relate to issues such as inspection regimes after exposure. Reduction in current levels of uncertainty, both about CMAS effects generally and concerning specific volcanic ash emissions, should benefit airlines and users of air transport.

4) Researchers working on high temperature protection systems. Some project outcomes will be of interest to a wide range of researchers. These include work on the adhesion of hot ceramic particles following high speed impact onto substrates. There should also be improvements in the understanding of (impurity-enhanced) sintering phenomena, which are relevant to a wide range of situations.

Dissemination, Impacts and Timescales
Dissemination will be mainly via publication in the open literature and a project website. The UK TBC Network (see http://www.msm.cam.ac.uk/mmc/index.php/research/tbc-network), an informal grouping of researchers and industrialists in the UK, will also be utilized. A workshop will be held in Cambridge, in collaboration with the Network. Close contact will be maintained throughout between UK and Indian collaborators, and with the industrial partners. Impact will partly be in the form of improved understanding of the effects of CMAS on the performance of aeroengines, particularly via effects on TBCs. This could contribute to the evolution of international agreements concerning exposure limits and guidelines for airlines flying in the vicinity of major volcanic emissions. Development of coating formulations with improved resistance to CMAS/VA-enhanced degradation would clearly have a strong impact. The timescale for such developments is probably of the order of 5 years (from the point when confidence in the background understanding has reached a suitable level).