Thermal shock resistance of air plasma sprayed thermal barrier coatings |
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Affiliation: | 1. Forschungszentrum Jülich GmbH, 52425 Jülich, Germany;2. Flame Spray North America Inc., USA;1. Division of Engineering Materials, Department of Management and Engineering, Linköpings Universitet, SE-58183 Linköping, Sweden;2. Siemens Industrial Turbomachinery AB, SE-61283 Finspong, Sweden;3. GKN Aerospace Engine Systems, SE-46181 Trollhättan, Sweden |
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Abstract: | The spallation resistance of an air plasma sprayed (APS) thermal barrier coating (TBC) to cool-down/reheat is evaluated for a pre-existing delamination crack. The delamination emanates from a vertical crack through the coating and resides at the interface between coating and underlying thermally grown oxide layer (TGO). The coating progressively sinters during engine operation, and this leads to a depth-dependent increase in modulus. Following high temperature exposure, the coating is subjected to a cooling/reheating cycle representative of engine shut-down and start-up. The interfacial stress intensity factors are calculated for the delamination crack over this thermal cycle and are compared with the mode-dependent fracture toughness of the interface between sintered APS and TGO. The study reveals the role played by microstructural evolution during sintering in dictating the spallation life of the thermal barrier coating, and also describes a test method for the measurement of delamination toughness of a thin coating. |
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Keywords: | Thermal barrier coatings Sintering Delamination Fracture Air plasma sprayed coating |
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