Thermal Stress Field in Plasma-Sprayed Ceramic Coatings

1992 ◽  
Vol 114 (2) ◽  
pp. 105-109 ◽  
Author(s):  
M. Ferrari ◽  
J. H. Harding
Keyword(s):  
Temperature Field ◽  
Thermal Stresses ◽  
Deposition Process ◽  
Ceramic Coatings ◽  
Coating Structure ◽  
Barrier Coatings ◽  
Thermal Stress Field ◽  
Plasma Sprayed ◽  
Orientation Pattern ◽  
Microstructural Data

In the cooldown phase of the deposition process, plasma-sprayed ceramic barrier coatings generate large residual stresses. In this paper, a scheme for the analysis of the thermal stresses is given, which accounts for the nonuniformity of the temperature field, and for the microstructure of the coating. The considered microstructural data include the morphology and orientation pattern of the porosities. The case of a coated sphere is studied, as an application. In this connection, the coating structure is computer-simulated, and the temperature profile is numerically determined.

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 Thermal Shock and Oxidation Stability Tests to Grade Plasma Sprayed Functionally Gradient Thermal Barrier Coatings

2019 ◽  
Vol 1 (1) ◽  
pp. 1-11
Author(s):  
Pasupuleti Kirti Teja ◽  
Parvati Ramaswamy ◽  
Narayana Murthy S.V.S.
Keyword(s):  
Thermal Barrier Coatings ◽  
Inconel 718 ◽  
Oxidation Stability ◽  
Ceramic Coatings ◽  
Functionally Graded ◽  
Yttria Stabilized Zirconia ◽  
Thermal Barrier ◽  
Stabilized Zirconia ◽  
Barrier Coatings ◽  
Plasma Sprayed

Functionally graded layers in thermal barrier coatings reduce the stress gradient between the overlaid ceramic coatings and the underlying metallic component. Introduced to alleviate early onset of spallation of the coating due to thermal expansion mismatch, this facilitates improvement in the life of the component. Conventional thermal barrier coatings typically comprise of duplex layers of plasma sprayed 8% yttria stabilized zirconia (ceramic) coatings on bond coated (NiCrAlY) components/substrates (Inconel 718 for example). This work highlights the superiority of plasma sprayed coatings synthesized from blends of the intermetallic bond coat and ceramic plasma spray powders on Inconel 718 substrates in three-layer configuration over the duplex layered configuration. Assessed through (a) thermal shock cyclic tests (at 1200oC and 1400oC) in laboratory scale basic burner rig test facility and (b) oxidation stability test in high temperature furnace (at 800oC and 1000oC) the functionally graded coatings of certain configurations exhibited more than double the life of the conventional 8% yttria stabilized zirconia duplex (double layer) coatings. Micro- and crystal structure analysis support the findings and results are detailed and discussed.

Numerical Analysis on Surface Fractures in Two-Layered Materials Subjected to Thermal Loading

2007 ◽  
Vol 353-358 ◽  
pp. 913-916
Author(s):  
Lian Chong Li ◽  
Chun An Tang ◽  
Jun Xing ◽  
Zheng Zhao Liang ◽  
Wei Jiang ◽  
...  
Keyword(s):  
Thermal Loading ◽  
Thermal Stresses ◽  
Mechanical Damage ◽  
Layered Materials ◽  
Ceramic Coatings ◽  
Thermal Barrier ◽  
Coating Materials ◽  
Barrier Coatings ◽  
Barrier Coating ◽  
Mesoscopic Level

With the knowledge of heterogeneous characteristics of thermal barrier coating materials at mesoscopic level, a coupled thermo-mechanical-damage (TMD Model) model was introduced and used to numerically quantify the thermal stresses and crack development of in thermal barrier coatings (TBCs) composite subjected to decreased temperatures. The effect of different surface precrack morphologies, such as precrack length and precrack density, on an interface crack subjected to thermal loading caused by a temperature change is presented. It provides us with a more sensible physical intuition and a more accurate mathematical for optimizing the design and the processing of ceramic coatings subjected to the coupled thermal-mechanical loading.

In Situ Measurement Within Plasma-Sprayed Zirconia Coatings Under Industrial Conditions

1998 ◽  
Author(s):  
N. Baradel ◽  
L. Bianchi ◽  
F. Blein ◽  
A. Freslon ◽  
M. Jeandin
Keyword(s):  
Thermal Stresses ◽  
Cooling System ◽  
Deposition Process ◽  
Thermomechanical Properties ◽  
Stress Generation ◽  
Plasma Gun ◽  
Damage Level ◽  
Point Bend ◽  
Plasma Sprayed

Abstract The thermomechanical properties of plasma-sprayed deposits strongly depend on residual stress distribution. This latter is mainly attributed to the relative torch/substrate velocity as well as to the cooling system location and efficiency. The determining of both quenching and thermal stresses, which are generated respectively during spraying stage and cooling stage, is then required to improve coatings quality. A rather simple apparatus, which consists in monitoring the curvature of a beam substrate during the whole deposition process, has been developed to work under industrial conditions. It has been applied to partially stabilized zirconia coatings performed onto stainless steel and cast iron substrates. Spraying temperature and plasma gun velocity have been selected as relevant parameters for this study about stress generation and mechanical release. Finally, four point bend tests have been performed on deposited samples to measure coating mechanical properties and to evaluate damage level.

scholarly journals Microstructural Characterization of Thermal Barrier Coatings Glazed by a High Power Laser

2016 ◽  
Vol 723 ◽  
pp. 247-251 ◽  
Author(s):  
Hong Zhou ◽  
Fei Li ◽  
Jun Wang ◽  
Bao De Sun
Keyword(s):  
Surface Roughness ◽  
Thermal Barrier Coatings ◽  
High Power ◽  
Microstructural Characterization ◽  
Ceramic Coatings ◽  
Thermal Barrier ◽  
High Power Laser ◽  
Power Laser ◽  
Barrier Coatings ◽  
Plasma Sprayed

Thermal barrier coatings have been widely used in in both energy and propulsion systems. Plasma-sprayed thermal barrier coatings have relatively high interconnected porosity and lamina structure, which bring out a low bond strength, and lead to a short thermal cycling life. Lasers can be used for modification of materials surface. In this paper, plasma-sprayed thermal barrier coatings were laser-glazed by a high power laser in order to modify the structures. The microstructure of laser-glazed TBCs is investigated. The change on surface roughness has been examined. The result indicates that a smooth and dense glazed surface with craters and a network of microcracks is obtained after laser-glazing. The laser-glazed region consists of a columnar microstructure. There are segmentation microcracks in the laser-glazed coatings, which don’t run through the coatings along thickness. Surface roughness has been reduced significantly for the laser treated ceramic coatings.

Coupled Thermal-Structural Finite Element Simulation of Ti-6Al-4V Alloy during Electrical Discharge Machining

2010 ◽  
Vol 135 ◽  
pp. 435-440
Author(s):  
Yan Wang ◽  
Feng Gao
Keyword(s):  
Finite Element ◽  
Temperature Field ◽  
Thermal Stress ◽  
Electrical Discharge ◽  
Thermal Stresses ◽  
Electrical Discharge Machining ◽  
Theoretical Models ◽  
Micro Cracks ◽  
Element Simulation ◽  
Thermal Stress Field

Theoretical models of temperature and thermal stress for Ti-6Al-4V during electrical discharge machining (EDM) process are established. Based on finite element method, the temperature field of EDM Ti-6Al-4V alloy is simulated firstly with the aid of ANSYS, the results can be used to predict the width and depth of the spark crater. The simulated results show that there is a high temperature distribution at the spark point while the zone is quite small. The thermal stress field is estimated using the results of the temperature field as input. Surrounding the spark crater, the thermal stresses are concentrated, where may cause micro-cracks.

The Thermoelastic Analysis of Chip-Substrate System

2004 ◽  
Vol 126 (3) ◽  
pp. 325-332 ◽  
Author(s):  
Linzhi Wu
Keyword(s):  
Temperature Field ◽  
Stress Concentration ◽  
Integrated Circuits ◽  
Thermal Stresses ◽  
Free Edge ◽  
Thermal Gradients ◽  
Substrate Structure ◽  
Thermal Stress Field ◽  
Electronic Assemblies ◽  
Free Edges

The presence of dissimilar material systems and thermal gradients introduces thermal stresses in multi-layered electronic assemblies and packages during fabrication and operation. The thermal stresses of the chip-substrate structure near free edges play an important role in determining the reliability of electronic packaging structures. Therefore, it is important to provide designers a good estimate of free edge stresses. According to the heat conduction mechanism of integrated circuits, the temperature field distribution in the chip and substrate is derived and solved when the chip works in a steady state. Taking the temperature field in the chip and substrate as the heat source, we solve the thermal stress field in the chip and substrate by using the technique of Fourier’s series expansion. The effects of geometric parameters of the chip and substrate on thermal stresses are analyzed. From the analysis of thermal stresses in the chip-substrate structure, it can be found that the stress concentration near free edges is more prominent. In the design of electronic packagings, the stress concentration near free edges which may cause cracking and delamination leading to the failure or malfunction of electronic assemblies and packages should be taken into account in details.

scholarly journals Modeling of Coating Stress of Plasma-Sprayed Thermal Barrier Coatings

2010 ◽  
Vol 24-25 ◽  
pp. 317-322 ◽  
Author(s):  
Masayuki Arai
Keyword(s):  
Residual Stress ◽  
Thermal Barrier Coatings ◽  
Deposition Process ◽  
Thermal Barrier ◽  
Multiple Cracks ◽  
Barrier Coatings ◽  
Stress Changes ◽  
Continuous Particle ◽  
Plasma Sprayed ◽  
Coating Stress

The surfaces of gas turbine components are coated with thermal barrier coatings (TBCs) using a plasma spraying technique. A lot of effort has been expended examining the TBC interfacial strength, however studies examining how residual stress is formed after the process and how the coating stress changes with temperature are limited. In this report, the residual stress prediction model is proposed based on the splat deposition process. A simplified model including the plasma sprayed process is developed based on shear-lag theory. The simplification is given in continuous particle deposition process. That is, continuous particle deposited coating is modeled as a single layer, which is called by "deposition layer". This deposition layer is assumed to impact directly onto the substrate. The binding layer is also introduced to express multiple cracks caused by quenching stress in splats and sliding deformation at splat boundary. It is shown that the numerical analysis has good agreement with the associated experiments.

Properties of ZrO2-7wt%Y2O3 Thermal Barrier Coatings in Relation to Plasma Spraying Conditions

1997 ◽  
Author(s):  
C. Funke ◽  
B. Siebert ◽  
D. Stöver ◽  
R. Vaßen
Keyword(s):  
Elastic Modulus ◽  
Plasma Spraying ◽  
Thermal Barrier Coatings ◽  
Bond Coat ◽  
Free Edge ◽  
Ceramic Coatings ◽  
Thermal Barrier ◽  
Normal Stresses ◽  
Barrier Coatings ◽  
Plasma Sprayed

Abstract Superalloy samples were coated with thermal barrier coatings (TBC). This TBC-system consisted of two layers. The first layer was a vacuum-plasma sprayed, corrosion resistant layer (MCrAlY) which also acted as a bond coat. The ceramic top layer was atmospheric-plasma sprayed Y2O3-stabilized ZrO2. In order to produce different microstructures, the plasma-spraying parameters for the production of the ceramic coatings were varied. The different ceramic coatings were characterized in terms of porosity and mean elastic modulus. The porosity distribution was also investigated due to its influence on the measured elastic modulus. To record the changes of the plasma sprayed Zirconia due to sintering, the mean elastic modulus of selected coatings was measured as a function of annealing time. One series of TBC-coated specimens was cyclically oxidized at a maximum temperature of 1100°C. After 500 h of thermal cycling, creep within the MCrAlY-bond coat led to a coating failure at both the internal beveled edge and free edge around the specimen. A finite element analysis study of the cyclic oxidation experiment was performed to gain insight into the stress redistributions within the bond coat as a function of time. During the initial temperature increase, critical tensile normal stresses developed above the MCrAlY-Zirconia interface at the free edge. However, these normal stresses became compressive for all following cooling cycles. On the other hand, large tensile normal stresses developed above the MCrAlY-Zirconia interface at the beveled edge during all the cooling cycles. Therefore, high normal stresses responsible for debonding were present within the ceramic coating during all cooling cycles with the most critical stresses occurring at the free edge during the first cooling cycle and near the beveled edge for all the following cooling cycles.

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