In order to improve gas turbine performances it is possible to decrease back flow gases in the high temperature combustion region of the turbo machine reducing shroud/rotor gap. Thick and Porous TBC systems and composite CoNiCrAlY/Al2O3 coatings made by Air Plasma Spray (APS) and composite CoNiCrAlY/Graphite coatings made by Laser Cladding were studied as possible high temperature abradable seal on shroud. Oxidation and thermal fatigue resistance of the coatings were assessed by means of isothermal and cyclic oxidation tests. Composite CoNiCrAlY/Al2O3 and CoNiCrAlY/graphite coatings tested for 1000 hours at 1100°C do not show relevant microstructural modifications. The oxidation resistance of new composite coatings satisfies Original Equipment Manufacturer (OEM) specification. Thick and Porous TBC systems passed the thermal fatigue test according to the considered OEM procedures. According to the OEM specification for abradable coatings the hardness evaluation suggests that this kind of coatings must be used with abrasive tipped blades. Thick and porous TBC coating has shown good abradability versus tipped blades.
Development and Investigation on New Composite and Ceramic Coatings as Possible Abradable Seals / U. Bardi, C. Giolli, A. Scrivani, G. Rizzi, F. Borgioli, A. Fossati, K. Partes, T. Seefeld, D. Sporer, A. Refke. - CD-ROM. - (2008), pp. 1-7. (Intervento presentato al convegno Thermal Spray Crossing Borders, ITSC 2008 International Thermal Spray Conference & Exposition tenutosi a Maastricht (NL) nel 2–4 Giugno 2008).
Development and Investigation on New Composite and Ceramic Coatings as Possible Abradable Seals
U. Bardi;F. Borgioli;A. Fossati;
2008
Abstract
In order to improve gas turbine performances it is possible to decrease back flow gases in the high temperature combustion region of the turbo machine reducing shroud/rotor gap. Thick and Porous TBC systems and composite CoNiCrAlY/Al2O3 coatings made by Air Plasma Spray (APS) and composite CoNiCrAlY/Graphite coatings made by Laser Cladding were studied as possible high temperature abradable seal on shroud. Oxidation and thermal fatigue resistance of the coatings were assessed by means of isothermal and cyclic oxidation tests. Composite CoNiCrAlY/Al2O3 and CoNiCrAlY/graphite coatings tested for 1000 hours at 1100°C do not show relevant microstructural modifications. The oxidation resistance of new composite coatings satisfies Original Equipment Manufacturer (OEM) specification. Thick and Porous TBC systems passed the thermal fatigue test according to the considered OEM procedures. According to the OEM specification for abradable coatings the hardness evaluation suggests that this kind of coatings must be used with abrasive tipped blades. Thick and porous TBC coating has shown good abradability versus tipped blades.
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