Erosion failure mechanism of EB-PVD thermal barrier coatings with real morphology

Abstract

The erosion behavior of EB-PVD thermal barrier coatings (TBCs) with real morphology was investigated based on finite element (FE) simulation. Firstly, an FE modeling method was developed to establish a geometric numerical model using a scanning electron microscope. Secondly, an empirical correlation between the depth of penetration and some characteristic parameters of the erodent particle (i.e. diameter, impact velocity and angle) was obtained by means of simulation. There is almost no difference in the depth of non-dimensional penetration between the real morphology and the simplified model; however, there are obvious differences in the dynamic kink band process in these two models. Due to the non-uniform size of the columnar structure of the EB-PVD TBCs, kink bands are irregular in the real morphology model, which redisplays this experimental phenomenon perfectly. Based on the plastic instability model, the relationship between particle impacting energy and kink band structure evolution in TBCs was set up. Lastly, the crack driving force to produce a surface crack was analyzed. The tensile stress along the column direction is small for TBCs under erosion conditions, with the critical dimensionless impact energy to start a crack being below 0.16 and about 0.195 for the real micro-structure and the simplified model, respectively. These results indicate that the real morphology would be more susceptible to erosion failure compared to the results of previous theoretical or numerical estimations.