Analysis Of Stress Field In Thermal Barrier Coatings Hot Corroded By CMAS

Thermal barrier coating(TBCs), as a high-temperature protective coating materials, are widely used in the aero-engine turbine blades due to its resistance to corrosion and high thermal insulation properties. However, with the increasing engine thrust-weight ratio, hot section of gas temperature rising. And CMAS high temperature corrosion failure becomes another major key issue constraining the thermal barrier coating life. However, the failure mechanism of CMAS hot corrosion TBCs is still unclear. Therefore, this article according to the experiment corrosion phenomena of CMAS hot corrosion EB-PVD TBCs. The CMAS corrosion mechanism action was divided into three parts: thermal mismatch, seepage, diffusionreaction, the impact of various theoretical models were established under the mechanism to analyse the stress distributions. The main researches are as follows:Thermal mismatch stress field analysis of TBCs corroded by CMAS: the cylinder geometric model of CMAS hot corrosion EB-PVD TBCs was established based on elasticity theory and the basic assumptions. The thermal mismatch stress between the coating and the CMAS was taken as boundary condition according to the coating/CMAS interface continuity conditions. And the thermal interface mismatch strain calculated, thus further calculated the radial and hoop stress field of TBCs due to thermal mismatch. And the stress were analyzed at last.Seepage stress field analysis of TBCs corroded by CMAS: the cylindrical geometry model of CMAS hot corrosion EB-PVD TBCs flowing process was established based on the theory of elasticity and basic assumptions. According to Darcy's law, CMAS flow equation in the TBCs was established. Additional volume force was considered in mechanical equilibrium equations by the CMAS penetration, then the other basic equations of elastic mechanics were adopted. The theoretical model of CMAS seepage in TBCs was established. The results was presented as radial and hoop stress field in TBCs caused by the CMAS. And the stress were analyzed at last.Diffusion-reaction stress field analysis of TBCs corroded by CMAS: the two-dimensional geometric model of CMAS hot corrosion EB-PVD TBCs was established. CMAS diffusion and reaction behavior in the top coating was investigated. A two-dimensional PFM that fully couples the Cahn-Hilliard equation and the constitutive equation was developed. For convenience, the coupled governing equations were solved by using a FEM-based numerical method through a commercial software package, COMSOL Multiphysics 5.0. The concentration of CMAS, the reaction-induced stress and volumetric strain in top coating corroded by CMAS were discussed, respectively. And the volume strain in the TBCs was predicted about 2.6% corroded by CMAS.