Structure and properties of plasma-sprayed ceramic coatings

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1984

OSTI ID:5954671

Shankar, N R

Plasma-sprayed ceramic coatings are increasingly being used in a variety of applications. Among these, ZrO/sub 2/-based thermal barrier coatings (TBC) are often used in applications involving thermal cycling such as in the case of gas turbine engines. Coating failure under these severe conditions is due to factors that include: stresses resulting from the thermal expansion mismatch between the ceramic coating and the metallic substrate; residual stresses; adhesion and interfacial reactions; coating composition; and phase transformations. In this study the effect of these factors on the integrity of ZrO/sub 2/-based and other oxide coatings are examined. Acoustic emission (AE) was used to study a variety of plasma-sprayed oxide coatings subjected to thermal cycling in the range 25/sup 0/ to 650/sup 0/C. Coatings of Al/sub 2/O/sub 3/, Al/sub 2/O/sub 3/-TiO/sub 2/, TiO/sub 2/, ZrO/sub 2/-5 wt% CaO and ZrO/sub 2/-20 wt% Y/sub 2/O/sub 3/, plasma sprayed onto the ends of a steel substrate, with and without a NiCrAl bond coat, were examined to relate acoustic activity to coating integrity. Al/sub 2/Onumber and TiO/sub 2/ coatings generated more AE counts than multicomponent Al/sub 2/Onumber-TiO/sub 2/ coatings. ZrO/sub 2/-based coatings yielded the least number of AE counts consistent with their better thermal cycling properties. The presence of the bond coat reduced AE counts in general. Results also indicated the formation of microcrack network during the initial cycles, in some coatings, which stabilized during subsequent cycles.

• Research Organization: State Univ. of New York, Stony Brook (USA)
• OSTI ID: 5954671
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360203* -- Ceramics
Cermets
& Refractories-- Mechanical Properties
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CALCIUM COMPOUNDS
CALCIUM OXIDES
CERAMICS
CHALCOGENIDES
COATINGS
OXIDES
OXYGEN COMPOUNDS
PERFORMANCE
SPRAYED COATINGS
SUBSTRATES
TITANIUM COMPOUNDS
TITANIUM OXIDES
TRANSITION ELEMENT COMPOUNDS
YTTRIUM COMPOUNDS
YTTRIUM OXIDES
ZIRCONIUM COMPOUNDS
ZIRCONIUM OXIDES