Thermal spraying. Determination of interfacial toughness of ceramic coatings by indentation

<p>Thermal spraying techniques are used to manufacture insulating coatings especially for demanding applications like fuel cells where normal insulating materials cannot be used. In electrical insulation applications, the mostly used coating materials are aluminum oxide (Al2O3), magnesium oxide (MgO) and magnesium aluminate (MgAl2O4). Dielectric properties of thermally sprayed ceramic coatings are strongly affected by ambient conditions, and in addition to this they are not well documented in the literature. In this paper the effects of environmental conditions on certain dielectric properties of a thermally sprayed coating are studied. DC resistivity as well as permittivity and losses at different frequencies at relative humidities of 20 % and 45 % at temperature of 20 °C, 40 °C and 60 °C will be reported in the paper for Al2O3 samples sprayed using HVOF (High Velocity Oxygen Fuel) technique. DC dielectric breakdown strength is also studied for the HVOF alumina coating at temperature of 20 °C and relative humidity of 20 %. Effects of ambient conditions and coating material composition are also analyzed.</p>

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Influence of Bondcoat Topography on the Properties of Suspension Sprayed YSZ Thermal Barrier Coatings

Thermal Spray 2021: Proceedings from the International Thermal Spray Conference ◽

10.31399/asm.cp.itsc2021p0009 ◽

2021 ◽

Author(s):

Filofteia-Laura Toma ◽

Julia Sagel ◽

Christoph Leyens ◽

Karel Slámečka ◽

Serhii Tkachenko ◽

...

Keyword(s):

Thermal Barrier Coatings ◽

Physical Vapor Deposition ◽

Thermal Spraying ◽

Ceramic Coatings ◽

Cycling Performance ◽

Thermal Barrier ◽

Oxide Ceramic ◽

Air Plasma ◽

Barrier Coatings ◽

Direct Laser

Abstract Intensive R&D work of more than one decade has demonstrated many unique coating properties; particularly for oxide ceramic coatings fabricated by suspension thermal spraying technology. Suspension spraying allows producing yttria-stabilized zirconia (YSZ) thermal barrier coatings (TBC) with columnar microstructure; similar to those produced by electron-beam physical vapor deposition (EB-PVD); and vertically cracked morphologies; with a generally low thermal conductivity. Therefore; suspension sprayed YSZ TBCs are seen as an alternative to EB-PVD coatings and those produced by conventional air plasma spray (APS) processes. Nonetheless; the microstructure of the YSZ topcoat is strongly influenced by the properties of the metallic bondcoat. In this work; direct laser interference patterning (DLIP) was applied to texture the surface topography of Ni-alloy based plasma sprayed bondcoat. Suspension plasma spraying (SPS) was applied to produce YSZ coatings on top of as-sprayed and laser-patterned bondcoat. The samples were characterized in terms of microstructure; phase composition and thermal cycling performance. The influence of the bondcoat topography on the properties of suspension sprayed YSZ coatings is presented and discussed.

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Reactive Plasma Spray

Production, Properties, and Applications of High Temperature Coatings - Advances in Chemical and Materials Engineering ◽

10.4018/978-1-5225-4194-3.ch012 ◽

2018 ◽

pp. 299-332

Author(s):

Mohammed Shahien

Keyword(s):

High Temperature ◽

Thermal Spraying ◽

Ceramic Coatings ◽

Reactive Plasma Spray ◽

In Situ Fabrication ◽

Reactive Plasma Spraying ◽

Reactive Plasma ◽

Nitride Coatings ◽

Promising Solution

Thermal spraying is a well-known coating technology with many variations in spraying techniques, feedstock materials and substrate materials. These unique variations increased its industrial applicability in different fields, including aerospace, automotive, chemical process, corrosion protection, and medical applications. However, one of the main limitations of thermal spray is the difficulty of depositing several nitride ceramics directly using conventional techniques. This is due to the decomposition of nitride particles under high temperature without a stable melting phase. This chapter presents reactive plasma spraying (RPS) technology as a promising solution for the in situ fabrication of several nitride ceramic coatings. The main attractive prospects of RPS for fabricating nitride coatings are specifically highlighted. Successful development of various high-temperature nitride coatings, such as AlN, Fe4N and Si3N4, are presented. Process optimization, the relationship between reaction and process parameters and the influence on coatings formation are comprehensively discussed.

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The Numerical Modeling of Thermal Stress Distribution in Thermal Barrier Coatings

Archives of Metallurgy and Materials ◽

10.1515/amm-2017-0221 ◽

2017 ◽

Vol 62 (3) ◽

pp. 1433-1437

Author(s):

A. Jasik

Keyword(s):

Thermal Stress ◽

Stress Distribution ◽

Thermal Barrier Coatings ◽

Bond Coat ◽

Thermal Spraying ◽

Ceramic Coatings ◽

Thermal Barrier ◽

Insulation Layer ◽

Barrier Coatings ◽

Thermal Stress Distribution

Abstract The paper presents the results of numerical calculations of temperature and thermal stress distribution in thermal barrier coatings deposited by thermal spraying process on the nickel based superalloy. An assumption was made to apply conventional zirconium oxide modified with yttrium oxide (8YSZ) and apply pyrochlore type material with formula La2Zr2O7. The bond coat was made of NiCoCrAlY. Analysis of the distribution of temperature and stresses in ceramic coatings of different thicknesses was performed in the function of bond-coat thickness and the type of ceramic insulation layer. It was revealed that the thickness of NiCrAlY bond-coat has not significant influence on the stress distribution, but there is relatively strong effect on temperature level. The most important factor influenced on stress distribution in TBC system is related with type and properties of ceramic insulation layer.

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Plasma spray process modelling using artificial neural networks: Application to Al2O3-TiO2 (13% by weight) ceramic coating structure

Journal de Physique IV (Proceedings) ◽

10.1051/jp4:2004120041 ◽

2004 ◽

Vol 120 ◽

pp. 363-370

Author(s):

S. Guessasma ◽

G. Montavon ◽

C. Coddet

Keyword(s):

Thermal Spraying ◽

Processing Parameters ◽

Ceramic Coatings ◽

Physical Models ◽

Spray Process ◽

Artificial Neural ◽

Artificial Neural Network Ann ◽

The Stability ◽

Experimental Values ◽

Physical Phenomena

Thermal spraying is a versatile technique of coating manufacturing implementing large variety of materials and processes. The manufacture control is constrained by the understanding of the physical phenomena occurring during the spraying. It is however penalized by the large number of processing parameters (up to 50), their interdependencies, their correlations with the coating attributes and the stability of the process. Numerous statistical, heuristic or physical models intended to response to these constrains, very often partially because considering some aspects of the process. This work aims at considering a more global approach based on a powerful statistical methodology using artificial intelligence. Following this approach, the physical phenomena are encoded in a structure called Artificial Neural Network (ANN). An application of the ANN methodology is discussed in the case of the APS spray process. Some processing parameters categories are related to some coating properties for alumina-titania (13% by weight) ceramic coatings. ANN optimization is presented and discussed. Predicted results show globally a well agreement with the experimental values. Some conclusions point out the advantages of the ANN on the conventional methods, such as the design of experiments, used usually to recognize the controlling factors in a process.

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