ISSN:
1573-4889
Keywords:
SCALE FRACTURE
;
OXIDE SCALES
;
ALUMINA
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract The isothermal- and cyclic-oxidation behavior ofthermal barrier coating (TBC) systems consisting ofvacuum plasma-sprayed (VPS) Ni-22Cr-10Al-1Y (wt.%) bondcoatings and air plasma-sprayed (APS)Y2O3-stabilized ZrO2 (YSZ) top coatings (onsingle-crystal superalloys) was investigated. Themicrostructures, flaw contents, and fracture behavior ofthe Al2O3 scales formed duringoxidation testing at 1150°C were characterized (by analysis of coating andscale fracture surfaces and metallographic crosssections). Significant localized fracture and bucklingof the Al2O3 scales that formedalong the bond-coat-top-coat interfaces were observed after cyclic oxidationof TBCs. However, substantial amounts of localized scaledamage did not induce rapid TBC failure. Decohesion ofthe columnar alumina scales on the rough bond-coat surfaces occurred by both internalAl2O3 fracture (parallel to themetal surface) and oxide-metal delamination. There weremicrostructural indications ofAl2O3 scale crack healing bysintering into planar arrays of voids. Alumina scales that formed onconvex NiCrAlY surfaces (with radii of 50 μm or less)often contained significant amounts of internal voids(along grain boundaries) after cyclic oxidation, whereas scales formed by isothermal oxidationcontained few visible voids. Accelerated void growth inAl2O3 scales on the irregularNiCrAlY surfaces appeared to be creep-related and wasattributed to the synergistic effects of geometric and thermalstresses.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1018870923397
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