This study examined the application of crack numerical density theory (CND) to determine the damage state of a thermal barrier coating (TBC) produced using the suspension plasma spray (SPS) technique. A TBC consisting of a partially stabilized zirconia topcoat was deposited upon an APS NiCoCrAl bondcoat and INCONEL 625 substrate. The TBC was exposed to an isothermal temperature of 1080 °C for a duration of up to 1300 h with specimens removed for examination at, 400 h, 800 h and 1300 h. Material properties after each exposure were determined and utilized to fit a CND model to predict the crack distribution within the topcoat following isothermal exposure. Probabilities of cracks developing within the topcoat that can bridge asperities (0.01% at 400 h, 2% at 800 h, and 11% at 1300 h) were determined indicating that CND may be a useful tool for predicting lifetimes of SPS-TBCs.

Crack numerical density, Fracture, Gamma statistics, Thermal barrier coating
Ceramics International
Department of Mechanical and Aerospace Engineering

Xiao, B. (Bingjie), Robertson, T. (Taylor), Huang, X, & Kearsey, R. (Rick). (2019). Fracture performance and crack growth prediction of SPS TBCs in isothermal experiments by crack numbering density. Ceramics International. doi:10.1016/j.ceramint.2019.09.258