Failure behavior of thermal barrier coatings on cylindrical superalloy tube under thermomechanical fatigue

Abstract

Failure behavior of thermal barrier coatings on cylindrical superalloy tube was investigated under thermomechanical fatigue (TMF). Two types of TMF tests, i.e. in phase (IP) and out of phase (OP), were performed in the temperature range of 450–850 °C. All tests were carried out under mechanical strain control at a given period of 300 s. The bond coat NiCrA1Y was produced by high velocity oxygen fuel (HVOF), and the top coat 7%Y2O3-ZrO2 was deposited by air plasma spraying (APS). The testing results showed that the OP TMF life was longer than the IP TMF one under the same mechanical strain amplitude. Observations of the fractured specimens revealed that the interface damage and cracking behavior in the two phasing conditions were different. In OP loading, the top coat was cracked and detached from the bond coat while no spallation was found in the IP loading.