Wspólnotowy Serwis Informacyjny Badan i Rozwoju - CORDIS

(1) Development of a new technique for deposition of Hafnium enriched Aluminide coatings onto super alloy substrates

A CVD-method for co-deposition of Hafnium enriched Aluminium diffusion layers onto super alloy substrates were developed. The process uses the fluoride route to generate vapour phase metal halide precursors. The evaporation temperatures of the fluorides determine the partial pressure of Hafnium and, ultimately, the Hafnium content in the diffusion layer and the layer thickness. Values up to 30µm thickness and contents up to 1at% Hf were obtained at a total system pressure of 100 hPa. The distribution perpendicular to the surface was very inhomogenous, therefore an annealing technique or an improved precursor feed has to be developed to get a smoother distribution of Hf in the layer.

Improved oxidation resistance of turbine blade super alloys allow higher combustion temperatures and longer maintenance intervals. Protective coatings containing reactive elements like Hf, Y, La, etc. improve the resistance against oxidative degradation. This was already obtained with additional active elements containing PtAl-diffusion layers. It was performed with the chloride route to serve the precursors. A 4-fold increased oxidation resistance has been reported. Similar effects can be expected by the technique developed by IOPW. It is applicable for simple Al layers but also for PtAl- diffusion layers. A code-position with Yttrium due to the projects master plan is under development.

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