Effects of Processing Parameters on the Deposition of Yttria Partially Stabilized Zirconia Coating During Suspension Plasma Spray

Chen, Xiaolong; Katayama, Seiji; Ohnuki, Takuma; Araki, Hiroshi; Watanabe, Makoto; Sakka, Yoshio

doi:10.1111/jace.14393

Cited by 22 publications

(9 citation statements)

References 45 publications

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“…The advantage of this technic called SPS (Suspensions Plasma Spraying) is to be able to elaborate very thin layers with various microstructures: columnar, dense, homogeneous, feathery… (Ref [25][26][27][28][29][30][31]. This microstructure depends on many parameters such as suspension load, suspension feed rate or substrate roughness (Ref [25][26][27][28]30). Seshadri et al (Ref 26) also recently showed that characteristics of the plasma flow, i.e., total gas flow rate and torch net power could affect coating microstructures in SPS.…”

Section: Introductionmentioning

confidence: 99%

Benefits of Hydrogen in a Segmented-Anode Plasma Torch in Suspension Plasma Spraying

et al. 2021

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Suspension plasma spraying (SPS) enables the production of various coating microstructures with unique mechanical and thermal properties. Aeronautical manufacturers have been working for fifty years to improve the thermal barrier coating (TBC) performances in gas turbines. Commercial plasma torches with a segmented anode that are characterized by stable plasma jets should enable a better control of the TBC microstructure. The addition of diatomic gases such as hydrogen in the plasma-forming gas affects the plasma jet formation and causes some instabilities. However, it enhances the thermal conductivity of the gas flow, the plasma mass enthalpy and the heat transfer to particles. This study aims to characterise and describe the coating microstructure changes of yttria-stabilised zirconia when gradually adding hydrogen with argon into the plasma gas mixture. The effect of hydrogen is weighted out due to the gas mass enthalpy, mean velocity at the nozzle exit and “hot zone” length of the plasma jet. The coating microstructures, which depend on these plasma jet parameters, will be mapped from feathery and porous to dense and cracked deposits depending on the spraying conditions.

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Section: Introductionmentioning

confidence: 99%

Benefits of Hydrogen in a Segmented-Anode Plasma Torch in Suspension Plasma Spraying

et al. 2021

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“…For example, yttria‐stabilized zirconia (YSZ) coatings, one of the most widely utilized thermal barriers, are frequently applied to target substrates via thermal plasma spray processes. [ 14–16 ] These processes expose the target substrate to molten particles or high‐temperature precursors throughout coating formation. As the temperatures required to synthesize YSZ as well as to convert particles to a molten state are exceedingly high (i.e., higher than the intended exposure temperature of the substrate), these processes can thermally damage the top layer of the substrate (often a bond coat).…”

Section: Introductionmentioning

confidence: 99%

Spray Pyrolysis‐Aerosol Deposition for the Production of Thick Yttria‐Stabilized Zirconia Coatings

et al. 2021

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Aerosol deposition (AD) is a coating technique wherein particles are impacted onto a target substrate at reduced pressures, and supersonic particle impact velocities lead to coating consolidation. The limiting step in AD application is often not supersonic deposition operation, but aerosolization of powder particles with the proper size distribution; the translational impact velocity is strongly size‐dependent. It is demonstrated that by directly synthesizing particles in the gas phase, size‐controlled ceramic particles can be injected into AD systems. This in situ formation step obviates the need for particle aerosolization. Ultrasonic spray pyrolysis (USP) is applied to produce yttria‐stabilized zirconia (YSZ), and USP is directly coupled with AD to produce consolidated, thick, YSZ coatings on metal substrates. USP‐AD yields YSZ coatings on stainless steel and aluminum substrates with porosities <0.20, which grow to thicknesses beyond 100 μm. Aerodynamic particle spectrometry and electron microscopy reveal that the depositing particles are 200 nm–1.2 μm in diameter, though each particle is composed of nanocrystalline YSZ. Supporting computational fluid dynamics calculations demonstrate that the YSZ particle impact speeds are above 300 m s−1. Thermal conductivity measurements demonstrate that USP‐AD coatings have conductivities consistent with those produced from high‐temperature processes.

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“…Many variables, such as pH, solid loading, dispersant, and media affecting the surface properties of YSZ particles have been investigated. 3,4 Electrostatic and electrosteric stabilization are the two well-known mechanisms which are used for the dispersion of particles. Electrostatic charging acts through the adsorption of ions on the surfaces of particles.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, it is important to stabilize the YSZ suspension, study its rheological behavior, and investigate the suspension repeatability properties. Many variables, such as pH, solid loading, dispersant, and media affecting the surface properties of YSZ particles have been investigated 3,4 …”

Section: Introductionmentioning

confidence: 99%

Effect of dispersion states (electrostatic/electrosteric stabilization) on particles arrangement in the yttria‐stabilized zirconia sediments

Shoja

Majidian

Nikzad

2021

Int J Applied Ceramic Tech

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In the present work, particle arrangement and their packing in the sediment layer of zirconia suspension were studied. To evaluate the particle settling, aqueous suspensions of zirconia nanoparticles were prepared in different dispersion states. In one state, Dolapix CE64 was used as a dispersant to provide electrosteric mechanism. In another state, pH of the suspension was adjusted at 4 to provide electrostatic mechanism. The other state was the combination of dispersant and pH adjustment which resulted in the most stable suspension. First of all, the stability of all dispersion states was evaluated by zeta potential, sediment volume (SV) and height, viscosity, and packing density (PD). Then, the sediment layers of all suspensions were characterized. Incorporation of electrostatic mechanism was resulted in a main decrease in viscosity with high surface charges, while electrosteric mechanism caused lower sedimentation of particles. Fall velocities of particles/agglomerates were estimated, and the influences of dispersion states on the particles fall velocities were characterized.The microstructural observation revealed homogeneous packing of particles in the sediment layer of the stable suspension demonstrating the proper dispersion of particles. Dolapix CE64 and pH adjustment resulted in a uniform arrangement of particles without agglomeration and spherical and regular granules with a uniform shape.

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Effects of Processing Parameters on the Deposition of Yttria Partially Stabilized Zirconia Coating During Suspension Plasma Spray

Cited by 22 publications

References 45 publications

Benefits of Hydrogen in a Segmented-Anode Plasma Torch in Suspension Plasma Spraying

Benefits of Hydrogen in a Segmented-Anode Plasma Torch in Suspension Plasma Spraying

Spray Pyrolysis‐Aerosol Deposition for the Production of Thick Yttria‐Stabilized Zirconia Coatings

Effect of dispersion states (electrostatic/electrosteric stabilization) on particles arrangement in the yttria‐stabilized zirconia sediments

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