Spalling failure of a thermal barrier coating associated with aluminum depletion in the bond-coat

Journal Article · Wed Mar 10 04:00:00 EST 1999 · Acta Materialia

DOI:https://doi.org/10.1016/S1359-6454(98)00407-8· OSTI ID:338432

Shillington, E A.G.; Clarke, D R ^[1]

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1. Univ. of California, Santa Barbara, CA (United States)

Although thermal barrier coatings (TBCs) are already being widely used in a variety of gas turbine and diesel engine applications, greater benefits are expected to accrue with TBCs that can be used in critical applications, namely those in which a loss of the coating would expose the underlying metal to a temperature in excess of its design specifications. A plasma-sprayed thermal barrier coating is observed to spall after oxidation at 1121 C from a CoNiCrAlY bond-coated superalloy at the interface between the thermally grown oxide (TGO) and the Zirconia thermal barrier coating (TBC). Phase characterization by photostimulated luminescence and X-ray diffraction, as well as microstructural characterization by scanning electron microscopy, indicates that the spalling is associated with the conversion of the initially formed {alpha}-alumina thermally grown oxide to {alpha}-chromia and a (CoNi)(CrAl) spinel. It is proposed that the phase conversion occurs after the alumina TGO has cracked on thermal cycling and the underlying bond-coat alloy is depleted of aluminum with concurrent enrichment of the oxide by Cr, Co and Ni. The observations suggest that monitoring the luminescence intensity as a function of oxidation time might form the basis of a nondestructive tool for detecting the onset of failure based on the disappearance of {alpha}-alumina.

• Sponsoring Organization: USDOE, Washington, DC (United States)
• OSTI ID: 338432
• Journal Information: Acta Materialia, Journal Name: Acta Materialia Journal Issue: 4 Vol. 47; ISSN 1359-6454; ISSN ACMAFD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
CHROMIUM ALLOYS
COBALT ALLOYS
COMPOSITE MATERIALS
HEAT RESISTING ALLOYS
INTERFACES
NICKEL ALLOYS
OXIDATION
PHASE STUDIES
SCALING
YTTRIUM OXIDES
ZIRCONIUM OXIDES