Thermophysical, mechanical and microstructural characterization of aged free-standing plasma-sprayed zirconia coatings

Cernuschi, F.; Bison, P.; Маринетти, С.; Scardi, Paolo

doi:10.1016/j.actamat.2008.04.067

Cited by 87 publications

(45 citation statements)

References 35 publications

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“…On the other hand, plasma-sprayed YSZ coating shows a lamellar microstructure with a limited interface bonding ( Ref 35). The nonbonded areas are virtually present in the coating as the cracks parallel to the interface of the YSZ coating/bond coat which reduce the thermal conductivity (Ref [36][37][38] and the toughness of the YSZ coating at the direction parallel to the surface of the YSZ coating (Ref 35, 39). The crack propagation will be initiated through the YSZ coating with a low toughness by the tensile force P, being the compressive stress exerted by the growth of protruding TGO, as illustrated by the model.…”

Section: Effect Of Mixedmentioning

confidence: 99%

Influence of TGO Composition on the Thermal Shock Lifetime of Thermal Barrier Coatings with Cold-sprayed MCrAlY Bond Coat

Zhang

2009

J Therm Spray Tech

102

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NiCoCrAlTaY bond coat was deposited by cold spraying to assemble thermal barrier coatings (TBCs). The microstructure of the cold-sprayed bond coat was examined using scanning electron microscopy. TBCs consisting of cold-sprayed bond coat and plasma-sprayed YSZ were pretreated at different conditions to form different thermally grown oxides (TGOs) before thermal cycling test. The influence of the TGO composition on the thermal cyclic lifetime was quantitatively examined through the measurement of the coverage ratio of the mixed oxides on the bond coat surface. The results showed that the bond coat exhibited a dense oxidation-free microstructure, and TGOs in different morphologies and constituents were present after thermal cyclic test. The formation of TGOs was significantly influenced by pretreatment conditions. Two kinds of TGO were detected on the surface of bond coat after the spallation of YSZ coatings. One is the a-Al 2 O 3 -based TGO and the other is the mixed oxide. It was found that the thermal cyclic lifetime is inversely proportional to the coverage ratio of the mixed oxides formed at the bond coat/YSZ interface. The high coverage ratio of the mixed oxide on the interface leads to the early spalling of YSZ coating.

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Section: Effect Of Mixedmentioning

confidence: 99%

Influence of TGO Composition on the Thermal Shock Lifetime of Thermal Barrier Coatings with Cold-sprayed MCrAlY Bond Coat

Zhang

2009

J Therm Spray Tech

102

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“…Extensive research has been conducted on these factors; results showed that strain tolerance and insulating abilities of the TBCs will decrease dramatically accompanied with the healing if micro-cracks, and shape of the pores changes during the sintering process (Ref [10][11][12][13]. The metastable tetragonal (t 0 -ZrO 2 ) phase of the as-sprayed coatings decomposes into equilibrium yttrium-lean tetragonal (tZrO 2 ) and yttrium-rich cubic (c-ZrO 2 ) phases at high temperature; upon further cooling, the t-ZrO 2 phase may transform to monoclinic (m-ZrO 2 ) phase.…”

Section: Introductionmentioning

confidence: 99%

Thermal Aging Behavior of Axial Suspension Plasma-Sprayed Yttria-Stabilized Zirconia (YSZ) Thermal Barrier Coatings

et al. 2014

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7.5YSZ thermal barrier coatings (TBCs) were deposited onto the stainless steel substrates using axial suspension plasma spraying (ASPS). Free-standing coatings were isothermally aged in air from 1200 to 1600°C for 24 h and at 1550°C for 20 to 100 h, respectively. Thermal aging behavior such as phase composition, microstructure evolutions, grain growth, and mechanical properties for thermal-aged coatings were investigated. Results show that the as-sprayed metastable tetragonal (t 0 -ZrO 2 ) phase decomposes into equilibrium tetragonal (t-ZrO 2 ) and cubic (c-ZrO 2 ) phases during high-temperature exposures. Upon further cooling, the c-ZrO 2 may be retained or transform into another metastable tetragonal (t 00 -ZrO 2 ) phase, and tetragonal fi monoclinic phase transformation occurred after 1550°C/ 40 h aging treatment. The coating exhibits a unique structure with segmentation cracks and micro/nanosize grains, and the grains grow gradually with increasing aging temperature and time. In addition, the hardness (H) and YoungÕs modulus (E) significantly increased as a function of temperature due to healing of pores or cracks and grain growth of the coating. And a nonmonotonic variation is found in the coatings thermal aged at a constant temperature (1550°C) with prolonged time, this is a synergetic effect of coating sintering and m-ZrO 2 phase formation.

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“…In our previous study, the thermal conductivity of plasma-sprayed Sm 2 Zr 2 O 7 coating was measured to be 0.38 W m À1 K À1 at 700°C, lower than that of YSZ and La 2 Zr 2 O 7 coatings ( Ref 6,14). In addition, YSZ TBCs exposed to high temperatures for extended period in service promote the microstructure reconfiguration, which modifies their mechanical and thermo-physical properties (Ref [15][16][17][18]. Therefore, an interest has been taken in Sm 2 Zr 2 O 7 coatings.…”

Section: Introductionmentioning

confidence: 98%

Effect of Thermal Aging on Microstructure and Mechanical Properties of Plasma-Sprayed Samarium Zirconate Coatings

Zhao

Zhou

et al. 2011

J Therm Spray Tech

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The rare-earth zirconates with the general formula of Ln 2 Zr 2 O 7 (Ln = rare-earth elements) having considerable low thermal conductivity and exhibiting good phase stability at high temperature have attracted particular interest in thermal barrier coating (TBC) applications. The Sm 2 Zr 2 O 7 coatings were deposited by plasma spraying, and the effect of thermal aging on their microstructure and mechanical properties was examined. The lamellar structure gradually disappeared with the temperature increasing for thermal aging. The evaluation by image analysis revealed that the amount of microcrack in coatings decreased with increasing aging temperature because of the increase in aspect ratio caused by microcrack healing, while no obvious change was observed in the spherical porosity. The as-sprayed Sm 2 Zr 2 O 7 coating exhibited low microhardness and elastic modulus, which increased with rise in aging temperature because of the microstructure reconfiguration; in addition, the ratio of microhardness to elastic modulus decreased with aging temperature increase, indicating a promotion in plastic property.

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Thermophysical, mechanical and microstructural characterization of aged free-standing plasma-sprayed zirconia coatings

Cited by 87 publications

References 35 publications

Influence of TGO Composition on the Thermal Shock Lifetime of Thermal Barrier Coatings with Cold-sprayed MCrAlY Bond Coat

Influence of TGO Composition on the Thermal Shock Lifetime of Thermal Barrier Coatings with Cold-sprayed MCrAlY Bond Coat

Thermal Aging Behavior of Axial Suspension Plasma-Sprayed Yttria-Stabilized Zirconia (YSZ) Thermal Barrier Coatings

Effect of Thermal Aging on Microstructure and Mechanical Properties of Plasma-Sprayed Samarium Zirconate Coatings

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