Effect of Morphology, Impact Velocity and Angle of the CaO-MgO-Al2O3-SiO2 (CMAS) Particle on the Erosion Behavior of Thermal Barrier Coatings (TBCs): A Finite Element Simulation Study

The erosion of the unmelted CaO-MgO-Al2O3-SiO2 (CMAS) particle is one of the dominating factors that causes microcracks in thermal barrier coatings (TBCs) when an aeroengine operates under actual service conditions. The microcracks provide a pathway for the erosion of the TBCs by the molten CMAS particles, which accelerates the failure of the coating. Herein a simplified model to mimic the erosion of YSZ (Y2O3 stabilized ZrO2) TBCs by the CMAS particles with high speed is proposed. The finite element method was utilized to systematically investigate the physical damage behaviors of the TBCs by the CMAS particles under various contact configurations, impact velocities and impact angles. We show that the contact configuration has a significant impact on the residual stress of the coating surfaces as well as the formation and types of microcracks. Furthermore, the increment of the erosion velocity gave rise to irreversible deformation around the point of contact, which aggravated the stress conditions of the top layer and led to the delamination failure of the coating. Finally, the larger the erosion angle, the more mechanical energy was converted into internal energy, which accumulated in the YSZ and caused it to finally delaminate.