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

Abstract

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 onmore » the disappearance of {alpha}-alumina.« less

Authors:
;  [1]
  1. Univ. of California, Santa Barbara, CA (United States)
Publication Date:
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
338432
Resource Type:
Journal Article
Resource Relation:
Journal Name: Acta Materialia; Journal Volume: 47; Journal Issue: 4; Other Information: PBD: 10 Mar 1999
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; OXIDATION; ZIRCONIUM OXIDES; YTTRIUM OXIDES; COBALT ALLOYS; NICKEL ALLOYS; CHROMIUM ALLOYS; ALUMINIUM ALLOYS; HEAT RESISTING ALLOYS; COMPOSITE MATERIALS; INTERFACES; SCALING; PHASE STUDIES

Citation Formats

Shillington, E.A.G., and Clarke, D.R. Spalling failure of a thermal barrier coating associated with aluminum depletion in the bond-coat. United States: N. p., 1999. Web. doi:10.1016/S1359-6454(98)00407-8.
Shillington, E.A.G., & Clarke, D.R. Spalling failure of a thermal barrier coating associated with aluminum depletion in the bond-coat. United States. doi:10.1016/S1359-6454(98)00407-8.
Shillington, E.A.G., and Clarke, D.R. Wed . "Spalling failure of a thermal barrier coating associated with aluminum depletion in the bond-coat". United States. doi:10.1016/S1359-6454(98)00407-8.
@article{osti_338432,
title = {Spalling failure of a thermal barrier coating associated with aluminum depletion in the bond-coat},
author = {Shillington, E.A.G. and Clarke, D.R.},
abstractNote = {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.},
doi = {10.1016/S1359-6454(98)00407-8},
journal = {Acta Materialia},
number = 4,
volume = 47,
place = {United States},
year = {Wed Mar 10 00:00:00 EST 1999},
month = {Wed Mar 10 00:00:00 EST 1999}
}