Numerical Simulation of Interfacial Cracking Behaviors in Thermal Barrier Coatings due to TGO Growth, TC Creep and Sintering

ABSTRACT Interfacial cracking is the main reason for the premature spallation of thermal barrier coatings (TBCs), which is directly related to the thermally grown oxide (TGO) growth and top coat (TC) sintering and creep. To elucidate the interfacial cracking behaviors, the interface cracking model of TBCs was developed. The effects of TGO growth, TC sintering, and creep on the interfacial crack evolution were studied. Results showed that significant increases in the tensile stress (13.4%) and shear stress (18.4%) at the interface were caused by sintering. The high tensile stress led the crack to nucleate in the valley region and spread along the TC/TGO interface towards the peak region. Sintering resulted in a 28.6% reduction in the time required for crack initiation. Furthermore, a large TC creep rate relaxed the interfacial stress significantly so as to postpone the time to reach the critical stress, while the high TGO growth rate accelerated interfacial cracking. Crack occurred after 90, 25, and 10 thermal cycles and propagated for 0.0028, 0.0345, and 0.0399 mm after 100 thermal cycles under the three different TGO growth rates, respectively. In addition, the TC creep rate and the TGO growth rate influenced the transition location of the interface fracture type (I and II).