Influence Of Thermal Barrier Coating Surface Treatment On CMAS Corrosion Resistance Of Thermal Barrier Coatings

Thermal barrier coatings（TBCs）have excellent thermal insulation properties and high temperature oxidation resistance.They have been widely used in aero-engine components to protect metal substrates and increase the inlet temperature of turbine engines.However,the engine is often affected by the corrosion of glassy oxides（CaO-MgO-Al₂O₃-SiO₂,CMAS）during operation.In this paper,on the basis of the original TBCs prepared by atmospheric plasma spray（APS）,the surface modification of TBCs with high current pulse electric beam（HCPEB）is used to improve the anti-CMAS corrosion performance of the coating,and extend the service life of engine components.First,the CMAS powder was prepared by the sintering and grinding method,and the CMAS powder meeting the experimental requirements was prepared by analyzing the physical properties of the CMAS powder.Then the CMAS powder was coated on the surface of the original coating prepared by APS technology to conduct high-temperature corrosion experiments,and the CMAS corrosion mechanism of the original coating was studied from the aspects of macroscopic morphology,microscopic morphology,element distribution and phase composition.The results show that when CMAS corrodes the original coating,on the one hand,it undergoes a thermochemical reaction with the coating to form m-ZrO₂ phase,which causes the coating to expand by 3%-5%in volume and increases the internal stress of the coating;CMAS fills the tiny pores of the coating,reduces the thermal expansion coefficient of the coating,and causes the thermal mismatch of the coating.Finally,the original coating has completely peeled off after 8 hours of corrosion by CMAS.Secondly,use HCPEB to modify the surface of the original coating to prepare a modified coating with stable phase structure,low surface roughness and modified layer thickness.Then,perform CMAS corrosion experiment on the modified coating to observe and analyze the modification.The CMAS corrosion mechanism of the coating.The results show that the modified coating is corroded by CMAS,and the surface of the coating still has good structural stability and phase stability.Although the speed of CMAS intruding into the modified coating is slightly faster than that of the original coating,the CMAS and the coating Ca₂Y₈（SiO₄）₆O produced by the reaction can hinder the further penetration of CMAS into the interior of the coating.Therefore,the structure of the modified coating is still intact after being corroded by CMAS for 8 hours,and the coating has not fallen off and failed.It has good resistance to CMAS corrosion.ability.Finally,in order to visually analyze the influence of CMAS on the stress field in TBCs,ANSYS finite element method was used to establish a coating model with no macro defects and macro defects to simulate the stress field distribution of the two coatings during the CMAS corrosion process.The simulation results show that CMAS corrosion will increase the internal stress in the coating,and the deeper the corrosion,the slower the corrosion rate.When the defects appear in the coating,CMAS will fill the defects and form a stress concentration area around the defects,and as the corrosion depth and the number of defects increase,the greater the internal stress of the coating,the easier it is to concentrate around the defect,making the coating easier Transverse micro-cracks are generated,causing delamination of the coating to fail.