Crack Formation and Architectural Evolution in Air Plasma Sprayed Top-Coats

Segmentation Cracks (SCs) in Thermal Barrier Coatings (TBCs) are recognized as a crucial microstructural asset for enhancing life of TBCs, by increasing in-plane strain tolerance. However, the crack formation dynamics and the structure evolution is complex, with a range of affects by feedstock morphologies, processing parameters, and substrate conditions. Understanding these effects on the driving forces for crack formation and quantitatively classifying the resultant architectures is critical for understanding their development in air plasma spray (APS) processing. The onset of cracking during deposition can be detected through use of in-situ curvature monitoring, which can pinpoint the formation conditions under which these cracks initiate and grow These formation insights can then be linked to the final coating architectures, quantifiable through measurement of crack density, position, and tortuosity. The effects of the powder morphology, spray parameters, and substrate temperatures have profound implications on the final coating architectures. These effects on resulting structures can ultimately be linked to performance, with furnace cycle durability as a critical metric for evaluation.