ISSN:
1573-4889
Keywords:
hot-corrosion testing
;
MCrAlY-type bond-coat alloys
;
EB–PVD thermal barrier coatings
;
oxide-scale fluxing
;
biomass-derived fuel combustion atmosphere
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract Model thermal-barrier coating (TBC) systems consisting of cast NiCrAlYsubstrates and electron-beam, physically vapor-deposited (EB–PVD)partially yttria-stabilized zirconia (PYSZ) coatings with three differentmicrostructures were tested in 1-hr cycles at 950°C under hot-corrosionconditions (sodium and sodium/potassium sulfates) likely to occur inbiomass-derived fuel-fired gas turbines. In contrast to conditionsinitiating Type I hot-corrosion attack, a modified test procedure wasused in this study where periodically salt-coated specimens were subjectedto an oxygen atmosphere while SOx was omitted, thus taking into account theessentially sulfur-free biomass fuel-combustion atmosphere. For comparison,similar tests were conducted on bare MCrAlY-type alloys. TBC failure byspallation of the PYSZ coating was observed between 300 and 500 1-hrcycles. Irrespective of PYSZ microstructure and deposit chemistry, failurewas primarily induced by crack formation and propagation within thevoluminous oxide scale formed as a result of hot-corrosion attack of themetal, rather than degradation of the ceramic layer. Since the major attackmode of the TBC seemed to be hot corrosion of the bond coat, this paperhighlights degradation mechanisms and microstructures of uncoated bond-coatcompositions. On the basis of the present results, implications of thefailure mode of EB–PVD PYSZ on in-service components are discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1004634400479
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