Assessment of TBC oxidation-induced degradation using compression tests
Résumé
Compression tests at room temperature are used to estimate the critical strain to spallation of EBPVD thermal barrier coating deposited on Ni based single crystals for blades used in aero-engines. The observation of fracture surfaces allows for investigating the location of delamination events leading to spallation, the eventual porosity at bond coat-alumina interface and kinetics of damage evolution. The effect of isothermal oxidation at 1,100 °C is presented for standard or low sulfur AM1 superalloy, and coating process variants. The degradation is shown to depend on the thermal-mechanical loading and varies from isothermal oxidation, cyclic oxidation and thermal-mechanical fatigue with hold time. These observations are consistent with the damage observed in blades in engine tests or in service. These tests are a useful complement to standard cyclic oxidation tests to identify engineering lifetime models.