Fracture Behavior and Lifetime Performance of Thermal Barrier Coatings in Thermally Graded Mechanical Fatigue Environments

The effects of the bond coat species on the thermal durability of TBCs were investigated through thermally graded mechanical fatigue tests till 900 cycles, with two tensile loads of 100 and 150 MPa and at two temperatures of 850 and 1100°C. When the load was 100 MPa at 850°C, the TBC with the APS bond coat showed delamination and cracks at the interface and on the surface, respectively, after about 250 cycles, while the TBC with the HVOF bond coat just showed long cracks at the interface after 900 cycles. As the temperature was increased to 1100°C or the load was increased to 150 MPa, delamination and/or cracks were created at the relatively low cycles in both TBCs, showing the severe effect of thermal stress (temperature effect). The HVOF bond coat is more efficient in improving thermal durability of TBC than the APS bond coat.