涉海环境CMAS+海盐腐蚀物特性及对EB-PVD热障涂层的腐蚀OA

To elucidate the coupled corrosion mechanism of calcium-magnesium-alumina-silicate(CMAS)and sea salts on advanced thermal barrier coatings(TBCs)under realistic marine service conditions,this study systematically investigates the physicochemical evolution,wetting behavior,and infiltration kinetics of CMAS+sea salt mixtures on electron beam physical vapor deposited(EB-PVD)YSZ coatings.CMAS mixtures containing 0,5wt.%(CMAS+5SS),and 10wt.%(CMAS+10SS)artificial sea salt was designed to simulate salt-laden environmental deposits.Differential scanning calorimetry(DSC),high-temperature contact angle measurements,and isothermal corrosion tests at 1 200℃were employed to quantify melting characteristics,interfacial wettability,and microstructural degradation.The results demonstrated that the incorporation of sea salt significantly altered the thermophysical properties of CMAS.The primary melting temperature decreased from 1 218℃for CMAS to 1 198℃and 1 196℃for CMAS+5SS and CMAS+10SS,respectively,accompanied by the emergence of low-temperature endothermic peaks(770℃)and a broadened liquid-phase interval.Simultaneously,the crystallization exothermic peak weakened,indicating suppressed crystallization ability.These changes were attributed to the formation of low-eutectic compositions and depolymerization of the silicate network induced by alkali and alkaline-earth ions(e.g.,Na+,Ca2+),which reduced melt viscosity and enhanced liquid stability over a wider temperature range.High-temperature wetting experiments at 1 220℃revealed a strong dependence of interfacial behavior on salt content.The equilibrium contact angle decreased from about 54.1° for CMAS to about 38.2°(CMAS+5SS)and 32.5°(CMAS+10SS)after 10 min,indicating substantially enhanced wettability.This improvement arose from reduced liquid-vapor and solid-liquid interfacial tensions due to melt structure depolymerization.The enhanced wettability directly facilitated rapid spreading and increased the effective contact area between the melt and coating surface.Corrosion experiments at 1 200℃—below the full melting temperature of CMAS—demonstrated that CMAS-sea salt mixtures could fully melt and actively infiltrate the EB-PVD coating.Short-term exposure(2-5 min)showed accelerated capillary-driven penetration along columnar gaps,with higher salt content leading to deeper and more uniform infiltration.Quantitative image analysis indicated that surface coverage of molten deposits remained above 85%for high-salt compositions,while significant dissolution of column tips and rounding of microstructural features were observed.The infiltration process followed the Washburn-Lucas mechanism,where reduced contact angle and viscosity synergistically increased penetration depth.After prolonged exposure(1 h),severe microstructural degradation occured.The original columnar architecture was largely destroyed,with intercolumnar gaps fully filled by glassy phases and a continuous reaction layer formed near the surface.Elemental mapping confirmed deep penetration of Si and Ca into the coating,accompanied by Zr redistribution,indicating active dissolution-reprecipitation reactions.Phase analysis revealed a pronounced tetragonal-to-monoclinic transformation of YSZ,particularly in high-salt conditions,suggesting accelerated phase destabilization.Additionally,thermal expansion mismatch between infiltrated glass phases and the ceramic matrix induced extensive crack networks and local structural collapse.The findings revealed a coupled degradation mechanism governed by melting point depression,viscosity reduction,wettability enhancement,and accelerated capillary infiltration induced by sea salt.This synergistic effect significantly intensified CMAS-induced damage in EB-PVD coatings,particularly by exploiting their columnar microstructure.The study provides new mechanistic insight into thermal barrier coating failure in marine environments and establishes a quantitative basis for designing corrosion-resistant coatings under high-temperature sea salt-containing conditions.