Thermal barrier coatings issues in advanced land-based gas turbines

Parks, W. P.; Hoffman, Eugene E.; Lee, Woo Y.; Wright, I.G.

doi:10.1007/s11666-997-0011-y

Cited by 40 publications

(14 citation statements)

References 4 publications

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“…Current combined-cycle plants have professed cycle efficiencies in the order of 49% and are capable of achieving environmental compliance for SO 2 and NO x with minimal effluent streams. The ultimate goal of these new systems is to reduce the cost of electricity by at least 10% [1].…”

Section: Introductionmentioning

confidence: 99%

High temperature oxidation of HFPD thermal-sprayed MCrAlY coatings

Belzunce

Higuera

Poveda

2001

Materials Science and Engineering: A

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NiCrAlY and CoNiCrAlY powders were thermal-sprayed using the high frequency pulse detonation method (HFPD) onto AISI 310 austenitic stainless steel samples in order to obtain dense, adherent high temperature oxidation resistant coatings. The cyclic oxidation behaviour in air of both types of coatings was determined at a maximum temperature of 1273 K. The porosity, internal oxidation (after the first 8-h oxidation cycle), hardness, coating thickness and substrate-coating adherence were not significantly modified by the high temperature oxidation cycles. The surface phase composition was evaluated throughout the tests using X-ray diffraction and scanning electron microscope techniques revealing the formation of a continuous and highly protective alumina layer. The oxidation kinetics of both coatings can be characterized by parabolic rate constants, which are very similar to those of pure alumina.

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Section: Introductionmentioning

confidence: 99%

High temperature oxidation of HFPD thermal-sprayed MCrAlY coatings

Belzunce

Higuera

Poveda

2001

Materials Science and Engineering: A

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“…1 However, recent studies have concluded that significant near-term progress in increasing turbine engine operating temperatures is more likely to come from the development of improved thermal barrier coatings ͑TBCs͒, typically yttria-stabilized zirconia ͑YSZ͒, than from the design of new alloys. 2 New processing techniques that result in TBC microstructures with lower thermal conductivity could lead either to higher operating temperatures of turbine engines, resulting in greater efficiency, or thinner coatings for the same operating temperature, which would reduce overall weight. Nanocrystalline YSZ coatings are of interest because they offer the possibility of lowering thermal conductivity, and may also provide additional benefits for TBC applications because of the possibility of improved toughness and ductility compared to that of coarser-grained ceramics.…”

mentioning

confidence: 99%

Grain-size-dependent thermal conductivity of nanocrystalline yttria-stabilized zirconia films grown by metal-organic chemical vapor deposition

Soyez¹,

Eastman²,

Thompson³

et al. 2000

Applied Physics Letters

178

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A grain-size-dependent reduction in the room-temperature thermal conductivity of nanocrystalline yttria-stabilized zirconia is reported for the first time. Films were grown by metal-organic chemical vapor deposition with controlled grain sizes from 10 to 100 nm. For grain sizes smaller than approximately 30 nm, a substantial reduction in thermal conductivity was observed, reaching a value of less than one-third the bulk value at the smallest grain sizes measured. The observed behavior is consistent with expectations based on an estimation of the phonon mean-free path in zirconia. © 2000 American Institute of Physics. ͓S0003-6951͑00͒05034-8͔The efficiency of gas turbine engines is dictated by the maximum sustained operating temperature of their typically Ni-or Co-based alloy turbine rotors. The development of new, higher temperature, high-strength, lightweight alloys is desirable. 1 However, recent studies have concluded that significant near-term progress in increasing turbine engine operating temperatures is more likely to come from the development of improved thermal barrier coatings ͑TBCs͒, typically yttria-stabilized zirconia ͑YSZ͒, than from the design of new alloys. 2 New processing techniques that result in TBC microstructures with lower thermal conductivity could lead either to higher operating temperatures of turbine engines, resulting in greater efficiency, or thinner coatings for the same operating temperature, which would reduce overall weight. Nanocrystalline YSZ coatings are of interest because they offer the possibility of lowering thermal conductivity, and may also provide additional benefits for TBC applications because of the possibility of improved toughness and ductility compared to that of coarser-grained ceramics. 3,4 The low thermal conductivity of YSZ ͑ϳ2.3 W/mK for high-density, polycrystalline material with a yttria-content of 10 mol. % at 20°C 5 ͒ is due primarily to phonon scattering by vacancies on the material's highly defective oxygen sublattice. 6 The potential for reduced thermal conductivity in nanocrystalline coatings arises from the predicted enhanced phonon scattering due to the presence of numerous closely spaced grain boundaries. For example, Klemens and Gell 6 have theoretically predicted that the room temperature thermal conductivity of 10 nm grain-sized YSZ containing 7 wt. % Y 2 O 3 will be decreased more than 50% compared to 1 m grain-sized YSZ of the same composition. The goal of the present study was to experimentally determine the effect of grain size on the room-temperature thermal conductivity of YSZ, thus contributing to the fundamental understanding of grain-size-dependent phonon scattering processes.Nanocrystalline YSZ films were grown by metal-organic chemical vapor deposition ͑MOCVD͒ using a low-pressure, horizontal, cold-walled deposition system. Yttrium b-diketonate ͓Y͑thd͒ 3 ͔ and zirconium t-butoxide ͓ZrOC͑CH 3 ͒ 4 ͔ 7 were chosen as precursor materials. Highpurity nitrogen was used as the precursor carrier gas. The precursors were mixed with high-purity ...

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“…This is achieved with Y 2 O 3 , CeO 2 , or MgO, the higher stabilization temperatures being obtained with Y 2 O 3 and CeO 2 . When the plasma-sprayed thermal barrier coatings were first used in the late 1980s both for aero-engines [167] and land-based turbines [168], the thermal insulation was achieved with zirconia stabilized by 8 wt% of yttria, PYSZ, which has been established as a standard for the last 20-30 years. Many studies have been devoted to these coatings and their qualities dependent on the powders used and the spray conditions.…”

Section: Zirconiamentioning

confidence: 99%