Mechanical Properties of Layered La2Zr2O7 Thermal Barrier Coatings
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Lanthanum zirconate (La2Zr2O7) has been proposed as a promising thermal barrier coating (TBC) material due to its low thermal conductivity and high stability at high temperatures. In this work, both single and double-ceramic-layer (DCL) TBC systems of La2Zr2O7 and 8 wt.% yttria-stabilized zirconia (8YSZ) were prepared using air plasma spray (APS) technique. The thermomechanical properties and microstructure were investigated. Thermal gradient mechanical fatigue (TGMF) tests were applied to investigate the thermal cycling performance. The results showed that DCL La2Zr2O7 + 8YSZ TBC samples lasted fewer cycles compared with single-layered 8YSZ TBC samples in TGMF tests. This is because DCL La2Zr2O7 TBC samples had higher residual stress during the thermal cycling process, and their fracture toughness was lower than that of 8YSZ. Bond strength test results showed that 8YSZ TBC samples had higher bond strength compared with La2Zr2O7. The erosion rate of La2Zr2O7 TBC samples was higher than that of 8YSZ samples, due to the lower critical erodent velocity and fracture toughness of La2Zr2O7. DCL porous 8YSZ + La2Zr2O7 had a lower erosion rate than other SCL and DCL La2Zr2O7 coatings, suggesting that porous 8YSZ serves as a stress-relief buffer layer.
Keywordsbond strength erosion lanthanum zirconate thermal barrier coating thermal cycling
This work received financial support from the US Department of Energy (grant no. DE-FE0008868, program manager: Richard Dunst) and Indiana University-Purdue University Indianapolis Research Support Funds Grant (RSFG) and International Research Development Fund (IRDF). Y.-G.J. also acknowledges financial support from the Human Resources Program in Energy Technology of the Korea Institute of Energy Technology Evaluation and Planning (KETEP), granted financial resource from the Ministry of Trade, Industry, and Energy, Republic of Korea (No. 20174030201460).
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