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  • 1
    facet.materialart.
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    Ceramic-coated metals can survive contact with hot working fluid (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Thermal barrier coatings (TBCs) have been developed as a means of protecting turbine blades and other engine hot section components whose surfaces are exposed to the most extreme operating conditions. By adding a thin, insulating ceramic oxide layer to an air-cooled turbine blade, the difference between the gas temperature and the metal temperature is further increased as a function of ceramic coating thickness, heat flux, and oxide thermal conductivity. An 0.04-cm thick ceramic layer can typically yield a 100-300 C temperature drop. Of the various techniques available for the deposition of thermal barrier coatings, the most common is that of plasma spraying. Significant improvements have been made in TBC durability through the use of bond coat compositions with increased oxidation resistance.
    Keywords: NONMETALLIC MATERIALS
    Type: Research and Development (ISSN 0160-4074); 26; 122-125
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Life modeling of atmospheric and low pressure plasma-sprayed thermal-barrier coating (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The cycles-to-failure vs cycle duration data for three different thermal barrier coating systems, which consist of atmospheric pressure plasma-sprayed ZrO2-8 percent Y2O3 over similarly deposited or low pressure plasma sprayed Ni-base alloys, are presently analyzed by means of the Miller (1980) oxidation-based life model. Specimens were tested at 1100 C for heating cycle lengths of 1, 6, and 20 h, yielding results supporting the model's value.
    Keywords: NONMETALLIC MATERIALS
    Type: Ceramic Engineering and Science Proceedings (ISSN 0196-6219); 5; 470-478
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Mechanical property measurements of plasma-sprayed thermal-barrier coatings subjected to oxidation (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Techniques have been developed for measuring the tensile properties of plasma-sprayed coatings which are used in thermal barrier applications. The measurements have included the average Young's modulus, bond strength and elongation at failure. The oxidation behavior of the bond coat plays an important role in the integrity and adhesion of plasma-sprayed thermal barrier coatings. This work studies the nature of the high temperature degradation on the mechanical properties of the coating. Furnace tests have been carried out on U-700 alloy with bond coats of NiCrAlY or NiCrAlZr and an overlay of ZrO2-8 percent Y2O3. Weight gain measurements on the coatings have been examined with relation to the adhesion strength and failure observations. The results from an initial study are reported in this work.
    Keywords: NONMETALLIC MATERIALS
    Type: Ceramic Engineering and Science Proceedings (ISSN 0196-6219); 5; 479-490
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Phase distributions in plasma-sprayed zirconia-yttria (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The distribution of phases in plasma-sprayed zirconia-yttria has been determined over a range of yttria levels from 0 to 26.1 molpct YO(1.5) using room temperature X-ray diffractometry. Pure, plasma-sprayed zirconia is composed almost entirely of the monoclinic phase. At levels of yttria between 4 and 10 percent, a quenched-in tetragonal phase predominates, and at higher levels the cubic phase predominates. The phase distributions are compared with previously reported test lives of thermal barrier coatings formed from these materials. Regions of optimal lives were found to correlate with regions having high amounts of the tetragonal phase, small but nonzero amounts of the monoclinic phase, and little or none of the cubic phase. Possible relationships between phase composition and coating performance are discussed.
    Keywords: NONMETALLIC MATERIALS
    Type: American Ceramic Society Bulletin (ISSN 0002-7812); 62; 1355-135
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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    Performance of thermal barrier coatings in high heat flux environments (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Thermal barrier coatings were exposed to the high temperature and high heat flux produced by a 30 kW plasma torch. Analysis of the specimen heating rates indicates that the temperature drop across the thickness of the 0.038 cm ceramic layer was about 1100 C after 0.5 sec in the flame. An as-sprayed ZrO2-8 percent Y2O3 specimens survived 3000 of the 0.5 sec cycles with falling. Surface spalling was observed when 2.5 sec cycles were employed but this was attributed to uneven heating caused by surface roughness. This surface spalling was prevented by smoothing the surface with silicon carbide paper or by laser glazing. A coated specimen with no surface modification but which was heat treated in argon also did not surface spall. Heat treatment in air led to spalling in as early as 1 cycle from heating stresses. Failures at edges were investigated and shown to be a minor source of concern. Ceramic coatings formed from ZrO2-12 percent Y2O3 or ZrO2-2O percent Y2O3 were shown to be unsuited for use under the high heat flux conditions of this study.
    Keywords: NONMETALLIC MATERIALS
    Type: Thin Solid Films (ISSN 0040-6090); 119; 195-202
    Format: text
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    NASA TECHNICAL REPORTS
  • 6
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    Thermal barrier coatings for aircraft engines: History and directions (1995)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Thin thermal barrier coatings for protecting aircraft turbine section airfoils are examined. The discussion focuses on those advances that led first to their use for component life extension and more recently as an integral part of airfoil design. It is noted that development has been driven by laboratory rig and furnace testing corroborated by engine testing and engine field experience. The technology has also been supported by performance modeling to demonstrate benefits and life modeling for mission analysis. Factors which have led to the selection of the current state-of-the-art plasma sprayed and physical vapor deposited zirconia-yttria/MCrAlY TBC's is emphasized in addition to observations fundamentally related to their behavior. Current directions in research into thermal barrier coatings and recent progress at NASA is also noted.
    Keywords: NONMETALLIC MATERIALS
    Type: Thermal Barrier Coating Workshop; p 5
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 7
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    Phase stability in plasma-sprayed, partially stabilized zirconia-yttria (1981)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Keywords: NONMETALLIC MATERIALS
    Format: text
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    NASA TECHNICAL REPORTS
  • 8
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    Introduction to life modeling of thermal barrier coatings (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Thermal barrier coatings may be applied to air-cooled turbine section airfoils to insulate such components from hot gases in the engine. The coatings, which typically consist of about 0.01 to 0.04 cm of zirconia-yttria ceramic over about 0.01 cm of NiCrAlY or NiCrAlZr alloy bond coat, allow increased gas temperatures or reduced cooling air flows. This, in turn, leads to marked improvements in engine efficiency and performance. However, certain risks are associated with designing for maximum benefits, and eventually a point is reached where coating loss would immediately jeopardize the underlying component. Therefore, designers must be able to accurately predict the life of a given bill-of-material coating in any particular design. The results of an in-house aeronautics, base research and technology program which is designed to provide the first steps towards developing mission-capable life-prediction models are outlined.
    Keywords: NONMETALLIC MATERIALS
    Type: Turbine Engine Hot Section Technology, 1984; 6 p
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 9
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    Oxidation-based model for thermal barrier coating life (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: A procedure is described for modeling the lives of thermal barrier coatings subjected to high-temperatrue environments. The models is used to calculate cycles-to-failure as a function of heating cycle duration. It is based on the presumption that oxidation is the single important time-dependent factor which limits the life of these coatings, and that oxidation-induced strains combine with cyclic strains to promote slow crack growth in the ceramic layer. Good agreement is obtained between calculated and experimental lives for specimens tested in a furnace. This shows that an oxidation-based approach is promising. The importance of reproducible specimen preparation is also discussed.
    Keywords: NONMETALLIC MATERIALS
    Type: American Ceramic Society, Journal (ISSN 0002-7820); 67; 517-521
    Format: text
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    NASA TECHNICAL REPORTS
  • 10
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    Ceramic coatings on smooth surfaces (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A metallic coating is plasma sprayed onto a smooth surface of a metal alloy substitute or on a bond coating. An initial thin ceramic layer is low pressure sprayed onto the smooth surface of the substrate or bond coating. Another ceramic layer is atmospheric plasma sprayed onto the initial ceramic layer.
    Keywords: NONMETALLIC MATERIALS
    Type: NAS 1.71:LEW-15164-1
    Format: application/pdf
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