The crack number density theory on air-plasma-sprayed thermal barrier coating

A crack number density (CND) theory model is developed for air-plasma-sprayed thermal barrier coating (TBC), which describes the evolution of crack number and size distribution as function of exposure time. The model is compared in good agreement with experimental measurements from quasi-isothermal-...

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Bibliographic Details
Published in:Surface & coatings technology 2019-01, Vol.358, p.347-352
Main Author: Wu, X.J.
Format: Article
Language:English
Subjects:
Coalescing
Crack evolution
Crack initiation
Crack number density
Crack propagation
Density
Fracture mechanics
Microcracks
Nucleation
Oxidation tests
Plasma spraying
Size distribution
Spallation
Thermal barrier coating
Thermal barrier coatings
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Summary:A crack number density (CND) theory model is developed for air-plasma-sprayed thermal barrier coating (TBC), which describes the evolution of crack number and size distribution as function of exposure time. The model is compared in good agreement with experimental measurements from quasi-isothermal-cyclic oxidation tests. Both the CND model and experimental observations indicate that thermally-grown oxides (TGO) are responsible for crack nucleation and growth. The model can be used to define TBC failure (spallation) by coalescence of microcracks into a maximum allowable crack size with a given probability. •For the first time, crack evolution in air-plasma sprayed TBC is described by the crack number density theory.•The damage evolution process consists of crack nucleation in Gamma distribution and crack growth by wedge-opening mechanism.•The integrated crack size distribution matches well with the experimental observations on an air-plasma sprayed TBC samples tested at 1200°C.•The model then offers a method for probabilistic TBC life prediction.
ISSN:0257-8972
1879-3347
DOI:10.1016/j.surfcoat.2018.11.058