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5476 |
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Wednesday, June 07, 2017, Hall 12 11:50 AM Aviation & Power Generation Industry I |
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Mitigation of molten salt infiltration by using a Gd2Zr2O7 suspension plasma sprayed coating for the next generation of thermal barrier coatings
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Benjamin Bernard / CEA-DAM, FRANCE Aurélie Quet*/ CEA-DAM, France Emmanuel Hervé/ CEA DAM, France Luc Bianchi/ Safran, France Aurélien Joulia/ Safran, France André Malié/ Safran Aircraft Engines, France |
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Suspension Plasma Spraying (SPS) has been widely studied for its ability to perform improved Thermal Barrier Coatings (TBCs). Particularly, Yttria-Stabilized Zirconia (YSZ) coatings presenting columnar microstructures showed low thermal conductivities (< 1 W.m-1.K-1) and high thermal lifetimes. In the next generation of gas turbine engines, expected to operate at higher temperatures, the degradation of TBCs by deposits of molten salts such as CMAS (CaO, MgO, Al2O3 and SiO2) will be a main issue for the durability of the high pressure turbine parts. Rare earth zirconates (RE2Zr2O7, mostly with RE = La, Gd) showed a mitigation behavior regarding CMAS infiltration, allowing to stop the attack. In the present study, Gd2Zr2O7 coatings were performed using suspension plasma spraying process. Homogeneous microstructures were produced. The contamination of the coatings with a CAS composition (23,5 wt. % CaO - 15,0 wt. % Al2O3 - 61,5 wt. % SiO2) showed the formation of an apatite blocking phase (Ca2Gd8(SiO4)6O2).The infiltration temperature was identified as a key parameter for mitigation strategy. Indeed, increasing the infiltration temperature from 1200 °C to 1300 °C allowed to significantly decrease the depth of the CAS penetration by increasing the reactivity between CAS and Gd2Zr2O7. |