Material Property Measurements on Thermal Barrier Coatings

1988 ◽  
Author(s):  
Christopher C. Berndt
Keyword(s):  
Acoustic Emission ◽  
Thermal Barrier Coatings ◽  
Material Property ◽  
Mechanical Response ◽  
Engineering Properties ◽  
Thermal Barrier ◽  
General View ◽  
Properties Of Coatings ◽  
Barrier Coatings ◽  
Tensile Adhesion

The material property measurements of thermal barrier coatings from cyclic furnace, thermal rig, thermal expansion, acoustic emission and tensile adhesion test methods are critically examined. Some basic engineering properties of coatings such as the elastic modulus have not been measured without ambiguity. Data of this nature is essential to the success of modeling studies. Insights into the mechanical properties of coatings have been gained by carrying out instrumented tensile adhesion tests. The general view of the coating deformation process is that the individual lamellae slide over each other and this promotes a “pseudo-ductility” response in the coating. Monitoring of the acoustic emission response of coatings during thermal cycling experiments suggests that there are two distinct cracking processes. The macro-cracking behaviour, indicated by a change in the acoustic emission count rate, is the predominant mechanism which leads to coating failure. It is further shown that the acceptance tests used by industry, although useful in ranking coatings in terms of a particular property, present no fundamental knowledge concerning the material properties of coatings. It is only when the phenomenological characteristics of the thermo-mechanical response of coatings is understood that coating development will substantially progress.

scholarly journals Influence of SiC Addition on Mechanical Behavior of Thermal Barriers with the Aid of Acoustic Emission

2021 ◽  
Vol 5 (1) ◽  
pp. 16
Author(s):  
David Jeronimo Busquets ◽  
Carlos Bloem ◽  
Amparo Borrell ◽  
Maria Dolores Salvador
Keyword(s):  
Acoustic Emission ◽  
Mechanical Behavior ◽  
Thermal Barrier Coatings ◽  
Wavelet Transforms ◽  
Coefficient Of Thermal Expansion ◽  
Microstructural Analysis ◽  
Thermal Barrier ◽  
Transfer Coefficients ◽  
Barrier Coatings ◽  
Thermal Barriers

The improvement of high temperature materials with lower heat transfer coefficients lead to the development of thermal barrier coatings (TBCs). One of the most widely used materials for thermal barrier coatings is Y2O3 stabilized ZrO2 (Y-TZP) because of its excellent shock resistance, low thermal conductivity, and relatively high coefficient of thermal expansion. The aim of this work is to study the TBCs mechanical behavior with the addition of SiC into the suspension of Y-TZP/Al2O3 by acoustic emission (AE). Additionally, a microstructural analysis and a finite elements model were carried out in order to compare results. The coatings were made by suspension plasma spray (SPS) on metal plates of 70 × 12 × 2 mm3. An intermetallic was deposited as a bond coating, followed by a coating of Y-TZP/Al2O3 with and without 15 wt.% SiC, with thicknesses between 87 and 161 μm. The AE becomes a fundamental tool in the study of the mechanical behavior of thermal barriers. The use of wavelet transforms streamlines the study and analysis of recorded sound spectra. The crack generation arises at very low stress levels.

STUDY ON PREPARATION TECHNOLOGIES OF THERMAL BARRIER COATINGS

2016 ◽  
Vol 24 (04) ◽  
pp. 1730004 ◽  
Author(s):  
TAO WANG ◽  
NING WANG ◽  
YANG LI ◽  
HAO WANG ◽  
JIE TANG ◽  
...  
Keyword(s):  
Thermal Barrier Coatings ◽  
Physical Vapor Deposition ◽  
Turbine Blades ◽  
Thermally Grown Oxide ◽  
Thermal Barrier ◽  
Properties Of Coatings ◽  
Preparation Technology ◽  
Barrier Coatings ◽  
Gradient Coating ◽  
Nano Coating

Thermal barrier coatings (TBCs) is one of the main key technology for the high-pressure turbine blades which are the main components of the high-performance aerospace engines. It offers protection for underline metallic components from corrosion, oxidation and localized melting by insulating the metal from hot gases in the engine core. The properties and lifetime of TBCs are greatly influenced by the preparation technology, which includes plasma spraying (PS), physical vapor deposition (PVD) and laser re-melting (LM). In this paper, three technologies used to prepare the TBCs are reviewed. Resulting features of coating fabricated by each technology are also discussed such as: the porosity, the thermally grown oxide (TGO), the erosion resistance, the thermal shock and so on. Especially, it is pointed out that the performances of gradient coating and nano-coating are better than the traditional coatings. In addition, it is widely accepted that laser can be applied to re-melt the PS coating and even directly clad the gradient coating. In the future, the traditional preparation technology should be improved continually in order to enhance the coating lifetime, enhance the properties of coating and lower the cost of process. Moreover, the researches on gradient-nano-structured coatings preparation are absent and should be done with emphasis since the nano-structure and gradient structure can both benefit the lifetime and properties of coatings.

Numerical Parametric Analysis of Bond Coat Thickness Effect on Residual Stresses in Zirconia-Based Thermal Barrier Coatings

2016 ◽  
Vol 35 (2) ◽  
pp. 201-207
Author(s):  
Musharaf Abbas ◽  
Hasan Junaid Hasham ◽  
Yasir Baig
Keyword(s):  
Thermal Barrier Coatings ◽  
Bond Coat ◽  
Mechanical Response ◽  
Thermally Grown Oxide ◽  
Thickness Effect ◽  
Thermal Barrier ◽  
Stress Profile ◽  
Barrier Coatings ◽  
Residual Stress Profile ◽  
Compressive Stresses

AbstractNumerical-based finite element investigation has been conducted to explain the effect of bond coat thickness on stress distribution in traditional and nanostructured yttria-stabilized zirconia (YSZ)-based thermal barrier coatings (TBC). Stress components have been determined to quantitatively analyze the mechanical response of both kinds of coatings under the thermal shock effect. It has been found that maximum radial tensile and compressive stresses that exist at thermally grown oxide (TGO)/bond coat interface and within TGO respectively decrease with an increase in bond coat thickness. Effect of bond coat thickness on axial tensile stresses is not significant. However, axial compressive stresses that exist at the edge of the specimen near bond coat/substrate interface decrease appreciably with the increase in bond coat thickness. Residual stress profile as a function of bond coat thickness is further explained for comparative analysis of both coatings to draw some useful conclusions helpful in failure studies of TBCs.

Acoustic emission assessment of interface cracking in thermal barrier coatings

2015 ◽  
Vol 32 (2) ◽  
pp. 342-348 ◽  
Author(s):  
Li Yang ◽  
Zhi-Chun Zhong ◽  
Yi-Chun Zhou ◽  
Wang Zhu ◽  
Zhi-Biao Zhang ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Thermal Barrier Coatings ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Interface Cracking

Acoustic Emission Evaluation of Thermal Barrier Coatings Using the Three Point Bending Test

1991 ◽  
Author(s):  
A. T. J. Verbeek ◽  
J. M. Houben ◽  
J. A. Klostermann
Keyword(s):  
Acoustic Emission ◽  
Thermal Barrier Coatings ◽  
Light And Electron Microscopy ◽  
Wide Band ◽  
Bending Test ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Bending Tests ◽  
Three Point Bending ◽  
Resonance Sensor

Thermal Barrier coatings were tested in three point bending tests, combined with acoustic emission evaluation. The test specimens consist of a 2 mm substrate with a 0.1 mm FeCrAlY bondcoat and a 0.3 mm ZrO2/Y2O3 93/7.8 weight % topcoat. Both the topcoat and the bondcoat were air plasma sprayed under varying conditions of the substrate cooling and the length of the plasma flame. On investigating the microstructure of the coatings, using light and electron microscopy, differences could be observed, due to the various spraying techniques. The coated specimens were tested in a tensile testing machine equiped with a special tool for three point bending tests. During bending, acoustic emissions from the coating were measured, using a two channel acoustic emission apparatus. Two types of AE sensors were used, namely a 150 kHz resonance sensor and a 0.1 −1 MHz wide band sensor. The various coatings show different AE patterns, especially the bondcoats which showed differences according to the spraying techniques. The use of wide band sensors had some advantages, however they were less sensitive than resonance sensors, they take signals that were received by the resonance ones. After testing, the specimens were prepared and microscopically investigated. Herewith it was possible to establish a relationship between the measured AE signal and the type of coating and coating failure.

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