Spalling failure of a thermal barrier coating associated with aluminum depletion in the bond-coat
- 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, Vol. 47, Issue 4; Other Information: PBD: 10 Mar 1999
- Country of Publication:
- United States
- Language:
- English
Similar Records
Oxidation-induced failure of thermal barrier coatings. Annual report, 1 October 1997--31 October 1998
Thermal barrier coatings