Evolution of surface morphology of thermo-mechanically cycled NiCoCrAlY bond coats

Anisotropic TGO rumpling in EB-PVD thermal barrier coatings under in-phase thermomechanical loading

“…(2), in a least-squares sense, separately to 25 randomly selected bond coat/TGO interface profiles digitized from SEM images in each of the relevant directions (perpendicular and parallel to the loading axis), with the average of those 25 values of 2δ and 2L reported in Table 1 were recently reported in [24]. The model simulations point out that the axial stress causes complicated undulation behavior influenced by many geometric and material parameters.…”

Comparison of the Failures during Cyclic Oxidation of Yttria-Stabilized (7 to 8 Weight Percent) Zirconia Thermal Barrier Coatings Fabricated via Electron Beam Physical Vapor Deposition and Air Plasma Spray

“…There is no evidence of rumpling for this bond coat. (Shi et al [22] reported rumpling for NiCoCrAlY bond coats when the cyclic exposures are carried out with a temperature gradient across the specimen.) Figure 33 indicates that the failure for Pt-aluminide bond coats occurs along the TGO/bond coat interface for isothermal exposures and by a ratcheting mechanism for 1-hour cycles (as described previously).…”

On TGO creep and the initiation of a class of fatigue cracks in thermal barrier coatings

“…One well established consequence of the compressive TGO stresses is that these can cause the TGO to be unstable against out-of-plane displacements ("surface instabilities") for some systems [1,10,12,15,16]. However, this particular TBC system does not exhibit these types of displacement instabilities when the top coat is present [16]. The growth stress at high temperature is limited due to creep properties of primarily the TGO but also the bond coat.…”

“…This mismatch stress combined with the TGO growth stress is typically in the range of 3 to 6 GPa [1,2,10,11,[16][17][18][19].…”