Combined effect of thermally grown oxide growth and calcium–magnesium–alumino–silicate infiltration in thermal barrier coating system

Abstract

In recent years, thermal barrier coating systems (TBCs) have been commonly used in aerospace equipment to enhance the performance of substrates. However, premature fracture of TBCs occurs due to the infiltration of calcium–magnesium–alumino–silicate (CMAS) particulates and excessive thickness of thermally grown oxide (TGO). To comprehensively understand the performance of TBCs, the effects of CMAS infiltration and TGO growth on the fracture behavior of TBCs were investigated. Two thermo-mechanical models were constructed to investigate the residual stress evolution of TBCs under the combined effect of CMAS infiltration and TGO growth. CMAS infiltration, TGO growth, expansion due to separation of the grain boundary, and tetragonal-to-monoclinic phase transformation were implemented by the ABAQUS subroutine. The buckle height and TGO growth trends were consistent with the experimental and theoretical results, respectively. The results indicate that the crack has a high probability of initiating and propagating at the off-peak of the topcoat (TC)/TGO interface owing to the maximum interfacial stresses. It can be concluded that in the case without TGO growth, CMAS infiltration results in an increase in the interfacial stresses. However, in the case with TGO growth, CMAS infiltration suppresses the interfacial stresses.