Abstract
Yb2O3-Gd2O3-Y2O3 co-doped ZrO2 (YGYZ) is considered to be a promising material in thermal barrier coating (TBC) applications. In this study, 2Yb2O3-2Gd2O3-6Y2O3-90ZrO2 (mol.%) (10YGYZ) feedstock candidates for air plasma spraying (APS) were prepared by calcination of agglomerated powders at 1100, 1200, 1300, 1400, and 1500 °C for 3 h, respectively. Incomplete solid solution was observed in calcined powders at 1100, 1200 and 1300 °C, and the 1500 °C calcined powder exhibited poor flowability due to intense sintering effect. The 1400 °C calcined powders were eventually determined to be the optimized feedstock for proper phase structure (cubic phase), great flowability, suitable apparent density and particle size distribution, etc. 10YGYZ TBCs with the optimized feedstock were prepared by APS, exhibiting pure c phase and good chemical uniformity. Controllable preparation of coatings with different porosity (i.e., 7%–9% and 12%–14%) was realized by stand-off distance adjustment.
Highlights
A typical spherical shape of these particles could be clearly observed, and the particle size of these powders falls in the range of 20–120 μm, which is in good agreement with the results obtained from the particle size analysis
The results suggest that the feedstock and the coating all have a single homogeneous c phase
A simple and efficient synthesis route, referred as “first agglomeration followed by calcination”, for preparation of 10YGYZ feedstock for air plasma spraying (APS) was explored in this study
Summary
Thermal barrier coatings (TBCs) have become indispensable in the practice of thermal protection towards hot section components of aircraft engines and gas turbines. Thanks to the wide application of TBCs, the operation temperatures of engines have continuously improved, which contributes to a great enhancement of engine efficiency and performance [1,2]. A TBC is typically composed of a ceramic top coat and a metallic bond coat. Owing to its excellent comprehensive properties, such as low thermal conductivity, good compatibility with the substrate originating from appropriate thermal expansion coefficient, and great mechanical properties, 7–8 wt.% Y2 O3 stabilized ZrO2 (YSZ) with an initial metastable tetragonal prime (t’) has been widely accepted as a classic material for TBC topcoat [1,2,3,4,5]
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