High Temperature Low-Cycle Fatigue Behavior of Thermal Barrier Coated Ni-Base Superalloy IN738LC

Damage behaviors of a thermal barrier coated (TBCed) Ni-base superalloy IN738LC were studied under high temperature low-cycle fatigue (LCF) condition. In this work, the HVOF process was selected as the spray process for bond coat. The CoNiCrAlY alloy was coated by 100 μm in thickness as the bond-coat on the Ni-base superalloy IN738LC substrate. And the 8YSZ was coated by 250 μm in thickness as the top-coat on the bond-coat. The LCF tests of TBCed IN738LC were carried out at 900℃ in air. The LCF lives of the TBCed IN738LC were compared with those of bare IN738LC and metal protective coated IN738LC specimen. The results of the LCF tests at 900℃ indicated that the LCF strength of the TBCed IN738LC is better than those of bare and metal protective coated IN738LC. The effect of thermal oxidation on the LCF life of the TBCed IN738LC was also investigated. The effect of thermal oxidation on the LCF life of the TBCed IN738LC was not significant. It was revealed from an observation of the damage morphologies that the cracking morphologies by LCF loadings were changed by the thermal oxidation.