Accession Number : ADA320578

Title :   Evaluation of Oxidation Damage in Thermal Barrier Coating Systems.

Descriptive Note : Technical memo.,

Corporate Author : NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CEN TER

Personal Author(s) : Zhu, Dongming ; Miller, Robert A.

PDF Url : ADA320578

Report Date : NOV 1996

Pagination or Media Count : 21

Abstract : A method based on the technique of dilatometry has been established to quantitatively evaluate the interfacial damage due to the oxidation in a thermal barrier coating system. Strain isolation and adhesion coefficients have been proposed to characterize the thermal barrier coating (TBC) performance based on its thermal expansion behavior. It has been found that, for a thermal barrier coating system consisting of ZrO2-8%Y2O3/FeCrAlY/4140 steel substrate, the oxidation of the bond coat and substrate significantly reduced the ceramic coating adherence, as inferred from the dilatometry measurements. The in-situ thermal expansion measurements under 30 deg C to 700 deg C thermal cycling in air showed that the adhesion coefficient, A sub i decreased by 25% during the first 35 oxidation cycles. Metallography showed that delamination occurred at both the ceramic/bond coat and bond coat/substrate interfaces. In addition, the strain isolation effect has been improved by increasing the FeCrAlY bond coat thickness. The strain isolation coefficient, Si, increased from about 0.04 to 0.25, as the bond coat thickness changed from 0.1 mm to 1.0 mm. It may be possible to design optimum values of strain isolation and interface adhesion coefficients to achieve the best TBC performance.

Descriptors :   *THERMAL PROPERTIES, *DAMAGE, *OXIDATION, *BARRIER COATINGS, MEASUREMENT, OPTIMIZATION, INTERFACES, ADHESION, SUBSTRATES, ALLOYS, IRON, CERAMIC MATERIALS, COATINGS, ALUMINUM, COEFFICIENTS, THERMAL EXPANSION, BONDING, CHROMIUM, METALLOGRAPHY, ZIRCONIUM OXIDES, YTTRIUM, THERMAL INSULATION, DILATOMETERS.

Subject Categories : Inorganic Chemistry
      Physical Chemistry
      Ceramics, Refractories and Glass
      Metallurgy and Metallography
      Thermodynamics

Distribution Statement : APPROVED FOR PUBLIC RELEASE