Finite element analysis of anti-spallation thermal barrier coatings

Unpredictable failure due to delamination and spallation of thermal barrier coating (TBC) systems used in hot parts of aircraft engines limits their service lifetime. Research in recent years has suggested that the residual stresses in the TBC system were affected by the presence of the thermally grown oxide (TGO) and which causes the spallation. A new idea to improve the anti-spallation character of the TBC system by applying an anti-spallation layer was presented in the current study and the stress distribution in TBCs produced with and without this layer was analyzed using the finite element method. The results show that the stress-state can be improved by the introduction of an additional anti-spallation layer on top of the partially stabilized zirconia (PSZ). The ultra high tensile stress after heating and compressive stress after cooling could be reduced from several GPa to several hundreds MPa or less. The stress perpendicular to the interface was also reduced. This would minimize the tendency of crack initiation on the interface, and hence the tendency of delamination and spallation of the TBC system.