Thermochemical Compatibility and Optical Properties of Gd2Zr2O7 and YSZ for Thermal Barrier Coatings

2012 ◽  
Author(s):  
Li Wang ◽  
Peigen Zhang ◽  
M. H. Habibi ◽  
S. M. Guo ◽  
Jeffrey I. Eldridge
Keyword(s):  
Wavelength Range ◽  
Treatment Time ◽  
Ceramic Coatings ◽  
Lattice Parameter ◽  
Ion Diffusion ◽  
Interface Failure ◽  
Free Standing ◽  
Turbine Engine ◽  
Heat Treated ◽  
Plasma Sprayed

In this paper, the phase stability of 50wt% gadolinium zirconate (Gd2Zr2O7, GZ) and 50wt% yttria-stabilized zirconia (YSZ) powder mixture heat treated at 1300 °C for different time was investigation by X-ray diffraction (XRD). Results showed that due to the gadolinium and yttria ion diffusion, the lattice parameter of GZ decreased with increase of the heat treatment time, and a part of YSZ had phase transformation which might be one of the reasons for the interface failure in double-layered or functionally gradient TBC systems. In addition, the room-temperature hemispherical reflectance, transmittance and absorptance spectra over the wavelength range from 0.8 to 15 μm were also determined for free standing GZ, YSZ and 50wt% GZ+50wt% YSZ plasma sprayed coatings. All of the ceramic coatings are semitransparent due to the high transmittance in the wavelength range <6 μm where turbine engine thermal radiation is concentrated. GZ is transparent to longer wavelengths than 8YSZ and has unique small peaks at wavelength 2.4 μm. The mixed coating is intermediate in behavior to GZ and YSZ coatings.

scholarly journals Enhancing Graphene Retention and Electrical Conductivity of Plasma-Sprayed Alumina/Graphene Nanoplatelets Coating by Powder Heat Treatment

Coatings ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 643
Author(s):  
Xiaoyu Wu ◽  
Shufeng Xie ◽  
Kangwei Xu ◽  
Lei Huang ◽  
Daling Wei ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Electrical Conductivity ◽  
Structural Integrity ◽  
Ceramic Coatings ◽  
Treatment Temperature ◽  
Graphene Nanoplatelets ◽  
Structural Defects ◽  
Temperature Plasma ◽  
Heat Treated ◽  
Plasma Sprayed

Burning loss of graphene in the high-temperature plasma-spraying process is a critical issue, significantly limiting the remarkable performance improvement in graphene reinforced ceramic coatings. Here, we reported an effective approach to enhance the graphene retention, and thus improve the performance of plasma-sprayed alumina/graphene nanoplatelets (Al2O3/GNPs) coatings by heat treatment of agglomerated Al2O3/GNPs powders. The effect of powder heat treatment on the microstructure, GNPs retention, and electrical conductivity of Al2O3/GNPs coatings were systematically investigated. The results indicated that, with the increase in the powder heat treatment temperature, the plasma-sprayed Al2O3/GNPs coatings exhibited decreased porosity and improved adhesive strength. Thermogravimetric analysis and Raman spectra results indicated that increased GNPs retention from 12.9% to 28.4%, and further to 37.4%, as well as decreased structural defects, were obtained for the AG, AG850, and AG1280 coatings, respectively, which were fabricated by using AG powders without heat treatment, powders heat-treated at 850 °C, and powders heat-treated at 1280 °C. Moreover, the electrical conductivities of AG, AG850, and AG1280 coatings exhibited 3 orders, 4 orders, and 7 orders of magnitude higher than that of Al2O3 coating, respectively. Powder heat treatment is considered to increase the melting degree of agglomerated alumina particles, eventually leaving less thermal energy for GNPs to burn; thus, a high retention amount and structural integrity of GNPs and significantly enhanced electrical conductivity were achieved for the plasma-sprayed Al2O3/GNPs coatings.

scholarly journals Ceramic Thermal Barrier Coatings for Turbine Engine Components

1982 ◽  
Author(s):  
D. S. Duvall ◽  
D. L. Ruckle
Keyword(s):  
Thermal Barrier Coatings ◽  
Ceramic Coatings ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Turbine Engine ◽  
Thermal Environments ◽  
Strain Tolerance ◽  
Endurance Testing ◽  
Plasma Sprayed ◽  
Cooling Air

The durability of plasma sprayed ceramic thermal barrier coatings subjected to cyclic thermal environments has been improved substantially by improving the strain tolerance of the ceramic structure and also by controlling the substrate temperature during the application of the coating. Improved strain tolerance was achieved by using ceramic structures with increased porosity, microcracking or segmentation. Plasma spraying on a controlled-temperature substrate also has been shown to improve durability by reducing harmful residual stresses. The most promising of the strain tolerant ceramic coatings have survived up to 6000 cycles of engine endurance testing with no coating or vane platform damage. In side-by-side engine tests, thermal barrier coatings have shown that they greatly reduce platform distress compared to conventionally coated vanes in addition to permitting reductions in cooling air and attendant increases in engine efficiency.

scholarly journals Strain Isolated Ceramic Coatings

1983 ◽  
Author(s):  
R. P. Tolokan ◽  
J. B. Brady ◽  
G. P. Jarrabet
Keyword(s):  
Ceramic Coating ◽  
Combustion Engine ◽  
Ceramic Coatings ◽  
Thermal Barrier ◽  
Turbine Engine ◽  
Shock Testing ◽  
Low Modulus ◽  
Metal Strain ◽  
Fiber Metal ◽  
Plasma Sprayed

The durability of thermally shocked high tempererature ceramic coatings on metal substrates can be dramatically improved using a fiber metal strain isolator between ceramic and metal. The fiber metal strain isolator is a compliant, porous and low modulus material which yields to control the stress on the ceramic coating during thermal cycling. Plasma sprayed strain isolated ceramic coatings .060” (1.5 mm) thick have shown excellent durability in thermal shock testing. The strain isolated ceramic coating is an excellent thermal barrier since both the ceramic and fiber metal are good insulators. Applications include ceramic thermal barrier coatings for gas turbine engine seals and turbine components, combustors, MHD electrodes, and internal combustion engine insulation.

Investigation Of Cracking Mechanisms Of Plasma Sprayed Alumina-13% Titania By Acoustic Emission

1995 ◽  
Vol 409 ◽  
Author(s):  
C.K. Lin ◽  
S.H. Leigh ◽  
R.V. Gansert ◽  
K. Murakami ◽  
S. Sampath ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
High Amplitude ◽  
High Energy ◽  
Physical Models ◽  
Free Standing ◽  
Water Stabilized Plasma ◽  
Heat Treated ◽  
Cracking Mechanisms ◽  
Point Bend ◽  
Plasma Sprayed

AbstractFree standing alumina-13% titania samples were manufactured using high power water stabilized plasma spraying. Heat treatment was performed at 1450°C for 24 hours and then at 1100°C for another 24 hours. Four point bend tests were performed on the as-sprayed and heat-treated samples in both cross section and in-plane orientations with in situ acoustic emission monitoring to monitor the cracking during the tests. Catastrophic failure with less evidence of microcracking was observed for as-sprayed samples. Energy and amplitude distributions were examined to discriminated micro- and macro-cracks. It was found that the high energy (> 100) and high amplitude (say > 60 dB) responses can be characterized as macro-cracks. Physical models are proposed to interpret the AE responses under different test conditions so that the cracking mechanisms can be better understood.

Characteristics of heat-treated plasma-sprayed CaO–MgO–SiO2-based bioactive glass–ceramic coatings on Ti–6Al–4V alloy

2014 ◽  
Vol 249 ◽  
pp. 97-103 ◽  
Author(s):  
Xianchun Chen ◽  
Mengjiao Zhang ◽  
Ximing Pu ◽  
Guangfu Yin ◽  
Xiaoming Liao ◽  
...  
Keyword(s):  
Bioactive Glass ◽  
Glass Ceramic ◽  
Ceramic Coatings ◽  
Heat Treated ◽  
Glass Ceramic Coatings ◽  
Plasma Sprayed

Study of Microstructure and Mechanical Properties of Yttrium Stabilized Zirconia Coating Deposited by Air Plasma Spray

2013 ◽  
Author(s):  
Chris P. Leither ◽  
Lauren E. Roy ◽  
Fardad Azarmi ◽  
X. W. Tangpong
Keyword(s):  
Mechanical Performance ◽  
Microstructural Characterization ◽  
Ceramic Coatings ◽  
Air Plasma ◽  
Zirconia Coating ◽  
Stabilized Zirconia ◽  
Free Standing ◽  
Bending Modulus ◽  
Sprayed Coating ◽  
Plasma Sprayed

Ceramic materials have been used extensively in different industries due to their excellent properties in high temperature environment. Thermally sprayed ceramic coatings offer outstanding properties which make them suitable candidate for advanced applications. These coatings exhibit excellent wear resistant properties with high adhesion strength. Depending on the application, ceramic coatings can be subjected to in-plane or out-of-plane loading during service. When the components are exposed to extreme change in temperature, consistent expansion, and shrinkage of the materials will cause crack initiation and propagation, resulting in spallation of the coating and consequently failure of the components. In this study, mechanical performance of plasma sprayed Yttrium stabilized Zirconia coating was investigated. A powder mixture of Yttrium stabilized Zirconia (ZrO2−8Y2O3) was air plasma sprayed on a cast iron substrate. Microstructural characterization of the as-sprayed coating was performed to evaluate the microstructural uniformity of the deposited samples using scanning electron microscopy (SEM). Three-point bend tests were performed to measure bending modulus of the free standing as-sprayed coating samples. Knoop indentation technique was also used as an alternate method to determine the modulus of the coating. Damping properties of the samples were also evaluated. This study pays special attention to the dependency of the mechanical performance on the microstructural characteristics of the thermal sprayed ceramic coatings.

Characteristics of Phosphoric Acid Sealed Ceramic Oxide Coatings

1996 ◽  
Author(s):  
E. Kumpulainen ◽  
M. Vippola ◽  
P. Vuoristo ◽  
P. Sorsa ◽  
T. Mäntylä
Keyword(s):  
Corrosion Resistance ◽  
Phosphoric Acid ◽  
Zirconium Oxide ◽  
Ceramic Coatings ◽  
Atmospheric Plasma ◽  
Curing Temperature ◽  
Oxide Coatings ◽  
Heat Treated ◽  
Plasma Sprayed ◽  
Hardness Values

Abstract Plasma sprayed ceramic coatings usually have relatively high open porosity in order to provide a good corrosion protection. By using sealants the porosity values can be reduced. In this study atmospheric plasma sprayed (APS) aluminium oxide, chromium oxide and zirconium oxide coatings were sealed by a phosphoric acid treatment. After impregnation the coatings were heat treated at a curing temperature of 400°C. Phosphoric acid was found to react with the coating material during the heat treatment. Wear resistance was evaluated by rubber wheel abrasion tests and corrosion resistance by electrochemical potentio-dynamic polarization tests. Hardness values were also measured. Corrosion resistance and hardness values of sealed coatings were remarkable better in comparison to the unsealed coatings. Rubber wheel abrasion resistances of the sealed coatings were equal to those of Al2O3, ZTA, SiC and Si3N4 sintered ceramics.

Electron microscopy studies of plasma-sprayed materials

1983 ◽  
Vol 41 ◽  
pp. 70-71
Author(s):  
K.R. Subramanian ◽  
A.H. King ◽  
H. Herman
Keyword(s):  
Plasma Spraying ◽  
Substrate Surface ◽  
Flame Temperature ◽  
Ceramic Coatings ◽  
Metallic Substrates ◽  
Hot Plasma ◽  
Almost All ◽  
Plasma Sprayed ◽  
Hostile Environments ◽  
Plasma Spraying Process

Plasma spraying is a technique which is used to apply coatings to metallic substrates for a variety of purposes, including hardfacing, corrosion resistance and thermal barrier applications. Almost all of the applications of this somewhat esoteric fabrication technique involve materials in hostile environments and the integrity of the coatings is of paramount importance: the effects of process variables on such properties as adhesive strength, cohesive strength and hardness of the substrate/coating system, however, are poorly understood.Briefly, the plasma spraying process involves forming a hot plasma jet with a maximum flame temperature of approximately 20,000K and a gas velocity of about 40m/s. Into this jet the coating material is injected, in powder form, so it is heated and projected at the substrate surface. Relatively thick metallic or ceramic coatings may be speedily built up using this technique.

Characterization of carbides in M50NiL

1991 ◽  
Vol 49 ◽  
pp. 606-607
Author(s):  
L. S. Lin ◽  
K. P. Gumz ◽  
A. V. Karg ◽  
C. C. Law
Keyword(s):  
Temperature Effects ◽  
Base Composition ◽  
Lattice Parameter ◽  
Control Surface ◽  
Carbide Formation ◽  
Particle Sizes ◽  
Low Carbon ◽  
Fee Structure ◽  
Heat Treated

Carbon and temperature effects on carbide formation in the carburized zone of M50NiL are of great importance because they can be used to control surface properties of bearings. A series of homogeneous alloys (with M50NiL as base composition) containing various levels of carbon in the range of 0.15% to 1.5% (in wt.%) and heat treated at temperatures between 650°C to 1100°C were selected for characterizations. Eleven samples were chosen for carbide characterization and chemical analysis and their identifications are listed in Table 1.Five different carbides consisting of M6C, M2C, M7C3 and M23C6 were found in all eleven samples examined as shown in Table 1. M6C carbides (with least carbon) were found to be the major carbide in low carbon alloys (<0.3% C) and their amounts decreased as the carbon content increased. In sample C (0.3% C), most particles (95%) encountered were M6C carbide with a particle sizes range between 0.05 to 0.25 um. The M6C carbide are enriched in both Mo and Fe and have a fee structure with lattice parameter a=1.105 nm (Figure 1).

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