The erosion of EB-PVD thermal barrier coatings: The competition between mechanisms

The normal impact of thermal barrier coatings by spherical particles is analysed by the finite element method in order to determine the transient stress state and potential for erosion. During the impact event, the deformation response can progress from elasto-dynamic to quasi-static elastic and then plastic. The precise sequence depends upon the size and velocity of the impacting particle, and upon the geometric and mechanical properties of the coating. Each deformation mechanism involves transient tensile stresses at characteristic depths within the coating, and these can lead to fracture of the columns from pre-existing flaws. Analytical solutions are presented that describe the transient stress state within the coating for each deformation mechanism; the analytical models are validated by independent finite element simulations in order to evaluate independent parameters. The analytical framework is used to construct deformation mechanism maps for the erosion of the thermal barrier coatings. It is concluded that erosion is a consequence of a set of potentially active deformation mechanisms.