Thermal Conductivity Behavior of Sol-Gel Post-Treated Thermal Barrier Coatings

2000 ◽  
Author(s):  
C.R.C. Lima ◽  
U. Senturk ◽  
R.S. Lima ◽  
C.C. Berndt
Keyword(s):  
Thermal Conductivity ◽  
Oxidation Resistance ◽  
Thermal Barrier Coatings ◽  
Bond Coat ◽  
Sol Gel ◽  
Thermal Barrier ◽  
Stabilized Zirconia ◽  
Barrier Coatings ◽  
Metallic Bond ◽  
Metal Ceramic

Abstract Thermal barrier coatings have been extensively used in several industrial segments. The material used as an insulator in such systems has been partially stabilized zirconia (PSZ) plasma sprayed over a metallic bond coat layer. The ceramic layer is usually porous, thus improving insulation properties. The porosity also increases gas permeability and, therefore, reduces oxidation resistance of the coating. Post-treatments have been applied to reduce the open porosity and improve oxidation resistance. In this work thermal barrier coatings were applied on low carbon steel substrates using two sets of bond coat, i.e., metallic and metal-ceramic. The metallic bond coat was NiCrAlY. The metal-ceramic bond coat was a mixture of NiCrAlY and 8% yttria partially stabilized zirconia, which were applied by simultaneous feeding to the plasma torch from two powder feeders. A sol-gel method was employed to impregnate the porous ceramic top coat with alumina or zirconia. The samples in the as-sprayed and post-treated condition were characterized using mercury intrusion porosimetry (MIP), thermal conductivity. KEY WORDS: Thermal Conductivity, TBCs, Sol-Gel.

Microstructure and Oxidation Resistance of Thermal Barrier Coatings with Different Ceramic Layer

2021 ◽  
Vol 320 ◽  
pp. 31-36
Author(s):  
Marek Góral ◽  
Tadeusz Kubaszek ◽  
Barbara Kościelniak ◽  
Marcin Drajewicz ◽  
Mateusz Gajewski
Keyword(s):  
Thermal Barrier Coatings ◽  
Bond Coat ◽  
Ceramic Layer ◽  
Thermal Barrier ◽  
Elemental Mapping ◽  
Stabilized Zirconia ◽  
Barrier Coatings ◽  
Bond Coats ◽  
All Ceramic ◽  
Zirconia Oxide

Thermal barrier coatings are widely used for protection of gas turbine parts against high temperature oxidation and hot corrosion. In present work the microstructural assessment of TBCs produced by atmospheric plasma spray (APS) method was conducted. Three types of ceramic powders were used: magnesia- stabilized zirconia oxide (Metco 210), yttria stabilized zirconia oxide (YSZ -Metco 204) and fine-grained YSZ – Metco 6700. As a base material the Inconel 713 was used as well and CoNiCrAlY was plasma sprayed (APS) as a bond coat. The thickness of all ceramic layers was in range 80 – 110 μm. The elemental mapping of cross-section of magnesia-stabilized zirconia showed the presence of Mg, Zr and O in outer layer. In the YSZ ceramic layer the Y, Zr and O were observed during elemental mapping. The isothermal oxidation test was conducted at 1100 °C for 500 h in static laboratory air. On all samples the delamination and spallation of ceramic layers was observed. Chemical composition analysis of coatings showed the presence of two areas: the first one contained elements from bond coats: Ni, Cr, Al, Co and second area contained O, Cr Co and O that suggest the scale formation. The obtained results showed the total degradation of all ceramic layers as a result of internal stresses in bond-coat. Microscopic analysis showed the areas with complete degradation of bond coats and formation of thick oxides layer.

scholarly journals Ceramic densification effect on corrosion resistance and thermal conductivity

2020 ◽  
pp. 11-17
Author(s):  
Emmanuel ACOSTA-PEREZ ◽  
Mercedes SALAZAR-HERNÁNDEZ ◽  
Juan Manuel MENDOZA-MIRANDA ◽  
Carmen SALAZAR-HERNÁNDEZ
Keyword(s):  
Thermal Conductivity ◽  
Corrosion Resistance ◽  
Thermal Barrier Coatings ◽  
Steel Surface ◽  
Sol Gel ◽  
Thermal Barrier ◽  
Densification Process ◽  
Barrier Coatings ◽  
The Core ◽  
Structure Changes

Thermal barrier Coatings (TBC) are a system of layers covering a surface with the aim to increase its insulation as well as protect the core of oxidation. In this paper the use of silica ceramics modified by polydimethylsiloxane (PDMS) as a new TBC for steel surface is proposed. The ceramics were obtained according to sol-gel methodology forming a stable sol mixing tetraethoxyetilsilicate (TEOS) at different percentage of PDMS (10, 20, 40 and 100%); the gelling was done using DBTL (dibutildilaurate tin) as a polycondensation catalyst. Therefore, the sol was applied on AISI-1018 steel surface by inmersion and a densification process is applied. The ceramic was characterized by infrared spectroscopy to observe its silica structure changes produced by the thermal treatment. Finally, the analysis the densification effect on properties on thermal conductivity and corrosion resistance was carried on.

Evaluation of Plasma Sprayed Thermal Barrier Coatings Using NDE and SEM

2007 ◽  
Author(s):  
Abbas Fahr ◽  
Catalin Mandache ◽  
Marc Genest ◽  
Weijie Chen ◽  
Xijia Wu ◽  
...  
Keyword(s):  
Thermal Barrier Coatings ◽  
Eddy Current ◽  
Thermal Imaging ◽  
Bond Coat ◽  
Elevated Temperatures ◽  
Internal Stresses ◽  
Thermal Barrier ◽  
Infrared Thermal Imaging ◽  
Barrier Coatings ◽  
Metallic Bond

Thermal barrier coatings (TBC) are used to protect the hot section components of gas turbine engines from high temperatures. A TBC system consists of a ceramic topcoat and a metallic bond coat sprayed or deposited onto the metal substrate. TBC failure is often associated with oxidation of the metallic bond coat at elevated temperatures via formation of thermally grown oxides (TGO) that cause internal stresses leading to the final spallation of the TBC. The present study explores the application of eddy current and infrared thermal imaging techniques for the detection of TGO in thermally-exposed TBC with a view of finding the damage criteria and a suitable solution for nondestructive evaluation (NDE) of TBC. The eddy current technique is based on the induction of an electromagnetic field and is sensitive to minute changes in electrical or magnetic properties of the test piece while infrared thermal imaging is based on thermal diffusion process and measures small differences in surface temperature. The NDE results are validated through destructive testing and microscopic examination of the TBC samples in as-sprayed condition and after exposure to elevated temperatures.

Thermophysical Properties of Samarium-Cerium Oxide for Thermal Barrier Coatings Application

2007 ◽  
Vol 336-338 ◽  
pp. 1773-1775 ◽  
Author(s):  
Chun Lei Wan ◽  
Wei Pan ◽  
Zhi Xue Qu ◽  
Ye Xia Qin
Keyword(s):  
Thermal Conductivity ◽  
Thermal Expansion ◽  
Thermal Barrier Coatings ◽  
Thermophysical Properties ◽  
Ceramic Coating ◽  
Fluorite Structure ◽  
Yttria Stabilized Zirconia ◽  
Thermal Barrier ◽  
Stabilized Zirconia ◽  
Barrier Coatings

Sm0.4Ce0.6O1.8 specimen with a defective fluorite structure was synthesized and its thermophysical properties were characterized for thermal barrier coatings (TBCs) application. At high temperature, Sm0.4Ce0.6O1.8 exhibited much lower thermal conductivity than 7wt% yttria-stabilized zirconia (7YSZ)-the commonly used composition in current TBCs. Sm0.4Ce0.6O1.8 also possessed large thermal expansion coefficient, which could help reduce the thermal mismatch between the ceramic coating and bond coat.

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