Abstract
Here TBC top coat failure and life time are considered as a two-step process, where step 1 is time to delamination macro-cracking and step 2 is time to through macro-cracking. This two-step failure mechanism comes directly from critical strain measurement data and traditional coating failure theory. The critical strain data was measured by using a four point bend test on preoxidized samples. Included in the model is damage accumulation due to bond coat oxidation and thermal fatigue. The damage terms in the model have their origins in acoustic emission data from cyclic oxidation samples. The life time model is then used in concert with measured thermally grown oxide micro-crack lengths from isothermal oxidation samples. Finally a full model is presented for isothermal and cyclic oxidation of APS–TBC.