Influence of Topcoat-Bondcoat Interface Roughness on Stresses and Lifetime in Thermal Barrier Coatings

A diffusion-based oxide layer growth model using real interface roughness in thermal barrier coatings for lifetime assessment

“…The residual vertical stresses in the topcoats near the topcoat-bondcoat interface were of major interest. The stresses in the topcoat further away from the interface did not change significantly between different interface profiles, as also observed in previous studies [6,11].…”

“…It has been observed that the failure occurs during the cooling cycle and the maximum stresses occur at the end of the cooling cycle [11]. Therefore, the stresses only at the end of cooling cycle were investigated.…”

“…A two-dimensional (2D) sinusoidal profile representing the topcoat-bondcoat interface roughness was used in finite element models by Vassen et al to evaluate the residual stresses developed in TBCs and it was observed that the time to stress inversion was shorter for samples which failed earlier in experiments [8]. In a recent work done by Gupta et al, real 2D and three-dimensional (3D) surface topographies were used in finite element models to compare different samples and it was again observed that the time to stress inversion was shorter for samples which failed earlier in experiments [11]. Based on the conclusion from these works, it can be assumed that the time to stress inversion according to the stress inversion theory could be implemented to compare coating lifetimes using both simplified as well as real topcoat-bondcoat interface topographies in a finite element model.…”

Role of internal oxidation on the failure of air plasma sprayed thermal barrier coatings with a double-layered bond coat

“…The CTE of the outer bond coat decreases with the increase of the internal oxides fraction. With more than 20 vol.% internal oxides, it is very close to that of the APS YSZ, 9.7×10 -6 /K ~ 11×10 -6 /K [26,29,30]. The Young's modulus of the outer bond coat increases with the increase of internal oxides, which is significantly higher than that of the substrate (Fig.…”

Simulation of damage and failure processes of thermal barrier coatings subjected to a uniaxial tensile load

“…However, no additional 3D information of the microstructure and the failure mechanisms could be obtained because of the 2D modeling method. Gupta [28] represented the 3D TC/BC interface successfully by using actual BC surface topographies scanned with a white-light interferometry technique before spraying the top coat layer. However, the representation of pores and microcracks with irregular shapes and distributions, which influence the mechanical behavior of the coatings dramatically, cannot be taken into account in this method [29,30].…”