Microstructure and Thermal Cycling Properties of Yb2O3 Modified Gd2Zr2O7 Thermal Barrier Coatings
The rare earth composite oxide of(Yb0.1Gd0.9)2Zr2O7(YbGdZrO)is a candidate material for novel thermal barrier coatings(TBCs),which can be potentially applied in higher temperatures.Both of single-ceramic-layer YbGdZrO and double-ceramic-layer YbGdZrO/YSZ TBCs were directly fabricated on top of(Ni,Pt)Al bond coat surface via electron beam physical vapor deposition(EB-PVD).The phase structure,chemical constituent,morphology and thermal cycling behavior of those TBCs were systematically investigated.The results show that the primary phase structure of the as-deposited YbGdZrO ceramic coating is single defective fluorite phase with co-existing of a small amount of Yb2O3.Compared with the single-ceramic-layer coating,each beam of columnar crystal clusters in the sample with double-ceramic-layer TBC is relatively slender,and obvious columnar gain gaps can be observed.The 1100 ℃ thermal cycling lifetime of double-ceramic-layer TBC is about 1.5 folds as that of single-ceramic-layer YbGdZrO coating.After long-term alternating thermal cycling,the transverse microcracks grow in the single-ceramic-layer YbGdZrO coating and extend to several microns above the interface of YbGdZrO/TGO layer,causing interfacial degradation and separation.Moreover,the Yb element contained in single-ceramic-layer has inwardly diffused into the TGO layer.Longitudinal cracks appear within the double-ceramic-layer coating,while both of YbGdZrO/YSZ and YSZ/TGO interfaces remain basically intact.After thermal cycling failure,transverse and vertical microcracks are formed in the TGO layer of the single-ceramic-layer and double-ceramic-layer specimens,and even further induce the phenomenon of intra-layer fracture separation.
electron beam physical vapor depositionthermal barrier coatingmodified Gd2Zr2O7thermal cyclinginterfacial separation
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