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Development of Bonding for Diffusion Barriers for the High Temperature Blades of Gas Turbines

Objective



The best materials for the blades (and vanes) of the hottest zone of gas turbine are today the Ni base superalloys tolerating a metal temperature of 950 1000C as protected against HT oxidation by an overlay of MCrAIY alloy or aluminides. At metal temperatures above 1000 C, the diffusion of Ni from the substrate to overlay destroys the oxidation resistance of the overlay, and vice versa, the diffusion of Al from the overlay to substrate embrittles the upper layers of the substrate. Therefore, suitable diffusion barriers are needed between the superalloy substrate and the overlay in order to make the metal temperatures above 1000 C applicable in the blades of gas turbines. In the inter European research programme COST 501, effective diffusion barriers were developed in 3 different stages reaching a capability to stop the diffusion at 1150 C in air for at least 400 hrs. The barriers were of a thickness of 1 4.5 micrometers. In spite of the success in stopping the harmful diffusions, the coated specimens with diffusion barriers and overlays suffered from disbanding and spalling in simulating burner rig tests, especially on the concave side of the blades. Therefore, the aim of the present basic research project is to develop sufficient bonding layers for these diffusion barriers so that they can be applied in gas turbines of power stations as well as of aircraft's, at metal temperatures of 1050 1100 C and 1100 1150 C, respectively. In the case of air cooled blades, the inlet temperatures of the gas would correspondingly be about 1250 C and 1350 C, and with hollow blades somewhat more. This would mean an increase of efficiency by about 5 %, and, in the case of aircraft's, a reduction of fuel consumption by about I %. On European level, the former would mean in the EU countries a saving of about 30 TWh/a in electricity generation, equal to about 1500 MECU/a; and the latter a saving of about 260 MECU/a. Of course, these savings can be achieved first as the results of the present basic research project are further developed to an industrial practice, e.g., by help of a subsequent B/E project. Thus, the objective of the present project is to produce a checked and certified basis for a larger industrial B/E project to search the above possibilities of the total development.
The project will be done in joint collaboration by 2 university units, I research center, and 3 companies in 4 different EU member countries, so that the development of gradient bondings and the laboratory scale structural studies and testing of properties will be done in the university units, the development of NDT testing and inspection in the research center, the simulating furnace and burner rig tests for landbase and aircraft turbines in one of the end user companies and in one of the university units, respectively. The evaluation of the results and the planning of the subsequent industrial project will be done jointly. The applicability of the results for the production of SMEs will be evaluated by one of the companies. The exploitation and dissemination of the results will be lead by a special Exploitation Manager from one of the end user companies. Totally the project will be composed of 6 different tasks with their own task leaders, and the tasks containing totally 20 sub tasks with own sub task leaders. The project takes a time of 4 years, but after 32 months there will be a mid term assessment, which depending on the received results decides the continuation.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Tampere University of Technology
Address
2,Korkeakoulunkatu 2
33101 Tampere
Finland

Participants (6)

AACHEN UNIVERSITY OF TECHNOLOGY
Germany
Address
Jülicher Str.344a
52056 Aachen
CESI CENTRO ELETTROTECNICO SPERIMENTALE ITALIANO GIACINTO MOTTA SPA
Italy
Address
Via Rubattino 54
Milano
CISE - Centro Informazioni Studi ed Esperienze SpA
Italy
Address
Via Reggio Emilia 39
20090 Segrate Milano
FRAUNHOFER-GESELLSCHAFT ZUR FOERDERUNG DER ANGEWANDTEN FORSCHUNG E.V.
Germany
Address
Universitaet, Gebaeude 37
66123 Saarbruecken
Hellenic Aerospace Industry Ltd
Greece
Address

32009 Schimatari
Scandinavian Surface Coating AB
Finland
Address
Raaseporin Teollisuusalue
10610 Tammisaari