Point Defect Effects on Hot Corrosion of Zirconia-Based Coatings
Abstract
Thermal barrier coatings are vulnerable to certain types of hot corrosion: sulfidation and vanadic attack. Stabilized zirconia, an often used thermal barrier coating, is degraded by dissolution of the stabilizing components, mass transport in the coating must occur. The presence of point defects in a crystalline solid greatly affect the transport properties in that solid. The nature and concentration of these defects can be altered which, in turn, can impart large changes in the transport properties of a material (eg. ionic conductivity and diffusion). In this study, we are determining the defect structures of yttria and ceria-stabilized zirconium oxides. Using electrical conductivity measurements, the activation energy of yttria-stabilized have been examined as a function of frequency, composition, and oxygen activity. Conductivity measurements on ceria-stabilized zirconia have shown anomalous results. At low oxygen activities, ZrO2-CeO2 samples did not reach equilibrium. The cause for this phenomenon has yet to be determined. Transport properties of molten Na2SO4 have been investigated to aid in understanding hot corrosion processes at 1173 K. An A.C. impedance technique for the total electrical conductivity, the potentiostatic polarization method for ionic transport number, and the steady state polarization method of Wagner and Hebb for the electronic conductivity were employed as a function of Na2O activity in the melt by controlling gas atmosphere.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 23, 1991
- Accession Number
- ADA232662
Entities
People
- D.-h. Kim
- G. Simkovich
- R. Reidy
Organizations
- Pennsylvania State University