Effect of the microstructure of suspension plasma-sprayed thermal barrier coatings on their thermal cycling damage

The suspension plasma spray (SPS) technique has recently attracted attention due to the variety of microstructures achievable using submicron spray particles mixed with a solvent to form a suspension. Thermal barrier coatings (TBCs) with a columnar microstructure can be obtained using SPS. Because of its unique columnar microstructure achieving high strain tolerance, a top coat sprayed using this technique can efficiently suppress thermal cycling damage in SPS-TBCs. However, there are few reports on the effect of microstructure on the damage behavior of SPS-TBCs with a columnar structure. In this study, the effect of the top coat microstructure on the thermal cycling fatigue of SPS-TBCs was investigated. The size of the complex oxide formed on the top coat-bond coat interface and the length of the cracks at the interface (formed as a result of thermal cycling) increase with the column diameter in the top coat of SPS-TBCs. The thermal spray conditions affect the thermal cycling fatigue life of SPS-TBCs. The SPS-TBC with fine columnar structure exhibits superior thermal cycling fatigue life.