Nickel base superalloys are normally protected against high temperature oxidation by MCrAlY type overlays. The diffusion of Ni from the superalloy and that of Al from the overlay causes, however, structural changes capable of causing spall off of the protectng layer. In a programme of the European concerted action cOST 501/II, the development of diffusion barriers for the temperature range of 1000-1100 deg C was started, and then continued in a BRITE-EURAM project, which has been concentrating on developing suitable bondings for the most promising diffusion barriers. On the basis of laboratory scale tests, suitable candidates for the diffusion barriers as well as for their bondings towards superalloys and the overaly have been found. These candidates will be tested during the last portion of the project on real blades in real gas turbine conditions.
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