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2112 |
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Wednesday, May 05, 2010, Olivia Room 1:40 PM Gas Turbines 3 |
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Ice dry stripping of TBC systems |
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Carlo Giolli* / Turbocoating SpA, Italy Andrea Scrivani / Turbocoating SpA, Italy Bruno Allegrini/ Turbocoating SpA, Italy Gabriele Rizzi/ Turbocoating SpA, Italy Andrea Giorgetti/ Turbocoating SpA, Italy Lars Engl/ Alstom Power, Switzerland Thomas Duda/ Alstom Power, Switzerland |
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Thermal barrier coatings are gaining considerable importance for the improvement the energetic efficiency of turbines. These materials are often applied on the surface of blades and are based on a layer of antioxidation material (mainly MCrAlY alloys) and a top layer that acts as proper thermal barrier (normally Yttria partially stabilized Zirconia). Coating removal is an important aspect in the production of these blades. ?Decoating? or ?stripping? is needed for the production of new components as well as for the reconditioning of existing ones. The present paper is dedicated to a new method of removal of the Zirconia ceramic layer. The method is based on the ice dry removal of the ceramic layer. This method will not impact on the roughness and morphology of the bond coat surface, making it suitable for a further step of TBC coating, without any further operation. This possibility will impact on the stripping costs and time, saving all the operator related to the qualification of the bond coat. The paper presents the process test to get the process set up and the characterization of the surfaces comparing the stripped ones with the one ?as coated? in new components, ready to be TBC coated. Optical and SEM microscopy, 3D profilometry have been used for characterization. Finally Thermal Cycling Fatigue test has been carried out on Stage II Vane in order to validate the procedure of stripping and recoating. |