Dynamic evolution of nonuniform temperature-stress distributions in continuously eroding thermal barrier coatings

Abstract

Erosion is the risk main factor for thermal barrier coating systems (TBCs). The resulting inhomogeneities introduce nonuniform temperature distributions, which affect temperature-dependent material behavior (e.g., growth of thermally grown oxide (TGO) and creep), complicating the stress states at the interfaces between the top coat (TC), TGO and the bond coat (BC). In this work, a finite element TBCs model considering dynamic erosion pit growth and TGO growth is built to evaluate the effects of the nonuniform erosion. The simulation results show that the growth of the erosion pit creates a high-temperature zone in TBCs, leading to the formation of oblique temperature gradients. Large temperature variations accelerate TGO growth and increase the thermal stress in TBCs, causing higher stress levels in the TC and BC layer during both the hot dwelling and cooling stages. Meanwhile, the gradually-growing erosion pit makes crack initiation and propagation more likely at interface zones located at both sides of the pit. Cracks occur in the maximum interfacial stress zones at the interface, which are off-peak during the hot dwelling stage and in-peak during the cooling stage. This work provides a relatively complete evaluation of erosion-induced effects, which is instructive for the design and operation of TBCs.