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  • 1
    Electronic Resource
    Electronic Resource
    Characterization of Alumina Scales Formed During Isothermal and Cyclic Oxidation of Plasma-Sprayed TBC Systems at 1150°C (1999)
    Springer
    Oxidation of metals 52 (1999), S. 31-76 
    Details
    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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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Relative permeabilities of a near critical binary fluid (1992)
    Springer
    Transport in porous media 9 (1992), S. 241-260 
    Details
    ISSN: 1573-1634
    Keywords: Flow in porous media ; critical phenomena ; consolute temperature ; relative permeability ; capillary desaturation ; wetting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Relative permeabilities were measured at very low interfacial tensions (IFT) for two-phase mixtures of methanol and hexane flowing through Clashach sandstone. These two components pass from a two- to a single-phase system as the temperature is increased above the critical solution temperature (CST). The interfacial tension between the coexisting phases approaches zero as the solution reaches miscibility. The phase behaviour of methanol and hexane mixtures has been well characterised allowing the calculation of relative permeabilities, saturations and capillary numbers. Flow data are reported for four different temperatures in the two-phase region (i.e., four values of IFT and capillary number). The capillary desaturation curve (CDC) for the strongly wetting methanol rich phase is also presented. In addition to the novel technique presented for measurement of relative permeability, the results indicate that relative permeabilities approach straight line functions very near the critical point. Furthermore, desaturation of the wetting phase was found to be dependent on the capillary number which, in turn, depends on the location of the mixture on the fluid phase diagram and the proximity to the critical temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00611969
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    Paper (German National Licenses)
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