A comparison of thermal shock behavior between currently plasma spray and supersonic plasma spray CeO2–Y2O3–ZrO2 graded thermal barrier coatings

The 5 layer structured ZrO2–7 wt.% Y2O3–18 wt.% CeO2 (C-YSZ) thermal barrier coatings (TBCs) by currently Plasma Spray (PS) and functionally graded TBCs system (FG-TBCs), composed of NiCoCrAlY bond coat (BC), C-YSZ/NiCoCrALY graded transition compound layer and a pure C-YSZ top coat, by recently developed Supersonic Plasma Spray system with dual powder feed ports were prepared. The experiment was performed to evaluate the thermal shock resistance of two different structured TBCs samples which were heated by a high heat flux of oxygen–acetylene flame to 1250 °C in a time interval of 10–15 s, and followed by water-quenching to ambient temperature using a multi-functional thermal shock tester in which 4 samples can be held simultaneously. The heating–cooling curves and surface morphology of specimens can also be observed by a CCD metalloscope and recorded on line through an accessorial computer system. The results show that thermal shock resistance of FG-TBCs was superior as its surface presents only little visible cracks after 200 cycles but 5 layer structured TBCs appear obviously delaminated after only 46 cycles.