Abstract
The phase and microstructural stability of thermal barrier coatings (TBCs) deposited using the solution precursor plasma spray (SPPS) process is studied as a function of thermal cycles at 1121 °C. In the SPPS process, an aqueous chemical precursor feedstock, that results in ZrO 2 –7 wt.% Y 2 O 3 (7YSZ) ceramic coating, is injected into the plasma jet and the coating is deposited on a metal substrate. The resulting coating has the desired non-transformable tetragonal phase structure and this phase is stable throughout the thermal cycling test. SPPS TBCs consist of ultra-fine splats and unmelted particles that include some non-pyrolyzed precursor. The non-pyrolyzed precursor in the coating was observed to decompose and crystallize during initial thermal cycling, which results in an increase of coating hardness. No sign of sintering of the ultra-fine splats in the coating was observed after 1090 cycles. The spacing of through-coating-thickness cracks (160–190 μm) does not change with thermal cycling, while the opening of cracks increases from around 0.4 μm at as-sprayed state to 1.7 μm at 40 cycles, and to 3.1 μm at 800 cycles.
Published Version
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