Synchrotron XRD Measurements Mapping Internal Strains of Thermal Barrier Coatings During Thermal Gradient Mechanical Fatigue Loading

2014 ◽  
Author(s):  
Kevin Knipe ◽  
Albert C. Manero ◽  
Stephen Sofronsky ◽  
John Okasinski ◽  
Jonathan Almer ◽  
...  
Keyword(s):  
High Temperature ◽  
Thermal Barrier Coatings ◽  
Mechanical Loading ◽  
Bond Coat ◽  
Thermal Gradient ◽  
Room Temperature ◽  
Material Behavior ◽  
Thermal Barrier ◽  
X Rays ◽  
Barrier Coatings

An understanding of the high temperature mechanics experienced in Thermal Barrier Coatings (TBC) during cycling conditions would be highly beneficial to extending the lifespan of the coatings. This study will present results obtained using synchrotron x-rays to measure depth resolved strains in the various layers of TBCs under thermal mechanical loading and a superposed thermal gradient. Tubular specimens, coated with Yttria Stabilized Zirconia (YSZ) and an aluminum containing nickel alloy as a bond coat both through Electron Beam - Physical Vapor Deposition (EBPVD), were subjected to external heating and controlled internal cooling generating a thermal gradient across the specimen’s wall. Temperatures at the external surface were in excess of 1000 °C. Throughout high temperature testing, 2-D high-resolution XRD strain measurements are taken at various locations through the entire depth of the coating layers. Across the YSZ a strain gradient was observed showing higher compressive strain at the interface to the bond coat than towards the surface. This behavior can be attributed to the specific microstructure of the EB-PVD-coating, which reveals higher porosity at the outer surface than at the interface to the bond coat, resulting in a lower in plane modulus near the surface. This location at the interface displays the most significant variation due to applied load at room temperature with this effect diminishing at elevated uniform temperatures. During thermal cycling with a thermal gradient and mechanical loading, the bond coat strain moves from a highly tensile state at room temperature to an initially compressive state at high temperature before relaxing to zero during the high temperature hold. The results of these experiments give insight into previously unseen material behavior at high temperature which can be used to develop an increased understanding of various failure modes and their causes.

Synchrotron X-Ray Diffraction Measurements Mapping Internal Strains of Thermal Barrier Coatings During Thermal Gradient Mechanical Fatigue Loading

2015 ◽  
Vol 137 (8) ◽  
Author(s):  
Kevin Knipe ◽  
Albert C. Manero ◽  
Stephen Sofronsky ◽  
John Okasinski ◽  
Jonathan Almer ◽  
...  
Keyword(s):  
High Temperature ◽  
Thermal Barrier Coatings ◽  
Mechanical Loading ◽  
Bond Coat ◽  
Thermal Gradient ◽  
Room Temperature ◽  
Material Behavior ◽  
Thermal Barrier ◽  
X Rays ◽  
Barrier Coatings

An understanding of the high temperature mechanics experienced in thermal barrier coatings (TBC) during cycling conditions would be highly beneficial to extending the lifespan of the coatings. This study will present results obtained using synchrotron X-rays to measure depth resolved strains in the various layers of TBCs under thermal mechanical loading and a superposed thermal gradient. Tubular specimens, coated with yttria stabilized zirconia (YSZ) and an aluminum containing nickel alloy as a bond coat both through electron beam-physical vapor deposition (EB-PVD), were subjected to external heating and controlled internal cooling generating a thermal gradient across the specimen's wall. Temperatures at the external surface were in excess of 1000 °C. Throughout high temperature testing, 2D high-resolution XRD strain measurements are taken at various locations through the entire depth of the coating layers. Across the YSZ, a strain gradient was observed showing higher compressive strain at the interface to the bond coat than toward the surface. This behavior can be attributed to the specific microstructure of the EB-PVD-coating, which reveals higher porosity at the outer surface than at the interface to the bond coat, resulting in a lower in plane modulus near the surface. This location at the interface displays the most significant variation due to applied load at room temperature with this effect diminishing at elevated uniform temperatures. During thermal cycling with a thermal gradient and mechanical loading, the bond coat strain moves from a highly tensile state at room temperature to an initially compressive state at high temperature before relaxing to zero during the high temperature hold. The results of these experiments give insight into previously unseen material behavior at high temperature, which can be used to develop an increased understanding of various failure modes and their causes.

Thermal Cycling Behavior of Lanthanum-Cerium Oxide Thermal Barrier Coatings Prepared by Air Plasma Spraying

2007 ◽  
Vol 336-338 ◽  
pp. 1759-1761 ◽  
Author(s):  
Wen Ma ◽  
Yue Ma ◽  
Sheng Kai Gong ◽  
Hui Bin Xu ◽  
Xue Qiang Cao
Keyword(s):  
Cerium Oxide ◽  
Plasma Spraying ◽  
Thermal Barrier Coatings ◽  
Bond Coat ◽  
Room Temperature ◽  
Thermal Barrier ◽  
Air Plasma ◽  
Air Plasma Spraying ◽  
Cyclic Testing ◽  
Barrier Coatings

Lanthanum-cerium oxide (La2Ce2O7, LC) is considered as a new candidate material for thermal barrier coatings (TBCs) because of its low thermal conductivity and high phase stability between room temperature and 1673K. The LC coatings with different La2O3 contents were prepared by air plasma spraying (APS) and their lifetime was evaluated by thermal cyclic testing from room temperature to 1373 K. The structures of the coatings were characterized by XRD and SEM and the deviation of the composition from the powder was determined by EDS analysis. Long time annealing for the freestanding coating at 1673K reveals that the near stoichiometric LC coating is stable up to 240h, and the stability decreases with increasing the deviation from stoichiometric LC composition. During thermal cyclic testing, spallation was observed within the top coat near the bond coat. It is considered that the effect of intrinsic stress caused by the coefficient of thermal expansion (CTE) mismatch between top coat and bond coat is larger than that of thermally grown oxide (TGO) and the bond adherence of top coat with TGO.

scholarly journals Cr 2 AlC MAX phase as bond coat for thermal barrier coatings: Processing, testing under thermal gradient loading, and future challenges

2019 ◽  
Vol 103 (4) ◽  
pp. 2362-2375 ◽  
Author(s):  
Jesus Gonzalez‐Julian ◽  
Georg Mauer ◽  
Doris Sebold ◽  
Daniel E. Mack ◽  
Robert Vassen
Keyword(s):  
Thermal Barrier Coatings ◽  
Bond Coat ◽  
Thermal Gradient ◽  
Max Phase ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Future Challenges

Thermal Cyclic Behaviour of Conventional YSZ and Mullite-YSZ Thermal Barrier Coatings

2020 ◽  
Vol 405 ◽  
pp. 417-422
Author(s):  
David Jech ◽  
Pavel Komarov ◽  
Michaela Remešová ◽  
Lucie Dyčková ◽  
Karel Slámečka ◽  
...  
Keyword(s):  
High Temperature ◽  
Thermal Barrier Coatings ◽  
Phase Stability ◽  
Bond Coat ◽  
Cyclic Oxidation ◽  
Thermally Grown Oxide ◽  
Atmospheric Plasma ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Mullite Phase

Nowadays commonly used thermal barrier coatings (TBC) are based on yttria stabilized zirconia (YSZ). Addition of mullite phase into the YSZ coating can improve resulting high temperature properties. The contribution focuses on high temperature cyclic oxidation behaviour of two TBC systems with different top coats (TC) deposited by the means of atmospheric plasma spraying. The initial mullite-YSZ powder mixture consisted of 29 vol. % of mullite and 71 vol. % of YSZ. The conventional TBC system consisted of ~ 150 µm thick NiCoCrAlYHfSi bond coat (BC) and ~ 300 µm thick YSZ top coat. The experimental mullite-YSZ (MYSZ) TBC system consisted of ~ 150 µm thick NiCoCrAlYHfSi bond coat, ~ 100 µm thick YSZ interlayer and ~ 200 µm thick mullite-YSZ top coat. The experimental TBC proved higher lifetime, durability and phase stability and also lower grow rate of thermally grown oxide (TGO) compared to conventional TBC. Lifetime, phase stability and changes in the microstructure of TBCs after the furnace cyclic oxidation test were evaluated by the means of scanning electron microscopy equipped with EDX analyzer and X-ray diffraction techniques. Oxidation kinetics of TGO was calculated based on thickness determined utilizing digital image analysis.

Life Prediction of High-Temperature MCrAlY Coatings Based on Microstructural Observations

2014 ◽  
Vol 922 ◽  
pp. 143-148 ◽  
Author(s):  
Robert Eriksson ◽  
Kang Yuan ◽  
Sten Johansson ◽  
Ru Lin Peng ◽  
Xin Hai Li
Keyword(s):  
High Temperature ◽  
Thermal Barrier Coatings ◽  
Bond Coat ◽  
Gas Turbines ◽  
Life Prediction ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Mcraly Coatings ◽  
Barrier Coating ◽  
Coating Composition

Thermal barrier coatings are commonly used in gas turbines for protection against high tem-perature and oxidation. Life prediction of oxidation protective coatingsmay be done bymicrostructure-based techniques such as -depletion based life criteria. In this study, a thermal barrier coating sys-tem, with an overlay NiCoCrAlY coating as bond coat, was oxidised up to 10000 h at 900 C. Themicrostructure was studied and related to Al depletion. It was found that a -depletion based lifecriterion could not be used for the studied coating composition and temperature as it would be tooconservative. A 0-depletion based model was instead suggested and supported by interdiffusion sim-ulation.

Preparation of 8YSZ and Double-Ceramic-Layer La2Zr2O7/8YSZ Thermal Barrier Coatings on GH4169 Superalloy Substrates and their Static High Temperature Oxidation Behaviour

2013 ◽  
Vol 749 ◽  
pp. 617-632 ◽  
Author(s):  
Liang Wang ◽  
You Wang ◽  
Xiao Guang Sun
Keyword(s):  
High Temperature ◽  
Thermal Barrier Coatings ◽  
Bond Coat ◽  
High Temperature Oxidation ◽  
Oxidation Behaviour ◽  
Atmospheric Plasma ◽  
Ceramic Layer ◽  
Thermal Barrier ◽  
Temperature Oxidation ◽  
Barrier Coatings

Thermal barrier coatings (TBCs) are very important ceramic coating materials due to their excellent performance at high temperature. Double-ceramic-layer (DCL) La2Zr2O7 (LZ)/8YSZ TBCs, nanostructured single-ceramic-layer (SCL) 8YSZ and conventional SCL 8YSZ TBCs with the same thickness were fabricated by atmospheric plasma spraying in the present work. The static high temperature oxidation behaviour of the three as-sprayed coatings at 1000 and 1200 was investigated systematically. The results indicated that the LZ/8YSZ has higher oxidation resistance than that of SCL 8YSZ. The addition of LZ ceramic layer can increase the insulation temperature, impede the oxygen transferring to the bond coat and decrease the formation rate of the thermally grown oxide (TGO). The formation of the oxidized isolated islands in the bond-coat has decreased the effective thickness of the TGO at the bond coat/ceramic layer interface due to the depletion of the metallic elements in the bond-coat.

A high-temperature displacement-sensitive indenter for studying mechanical properties of thermal barrier coatings

2004 ◽  
Vol 19 (1) ◽  
pp. 351-356 ◽  
Author(s):  
Chang-Hoon Kim ◽  
Arthur H. Heuer
Keyword(s):  
Elastic Modulus ◽  
High Temperature ◽  
Thermal Barrier Coatings ◽  
Room Temperature ◽  
Elastic Recovery ◽  
Thermal Barrier ◽  
Columnar Microstructure ◽  
Barrier Coatings ◽  
Similar Composition ◽  
Barrier Coating

Electron beam physical-vapor-deposited Y2O3-stabilized ZrO2 thermal barrier coating (TBC) samples were indented from room temperature to 900 °C using an instrumented high-temperature vacuum displacement-sensitive indenter. Hardness and elastic modulus were determined from the load–displacement curves recorded during indentation. Both the hardness and the elastic modulus of the TBCs were much lower than those of dense ceramics of a similar composition; this is attributed to the increased compliance that results from the porous columnar microstructure of the TBCs. In addition, the TBCs showed an unusual absence of elastic recovery at the residual indents compared to the dense ceramics.

Thermal Fatigue of Thermal Barrier Coatings by Atmospheric Plasma Spraying

2008 ◽  
Vol 385-387 ◽  
pp. 405-408 ◽  
Author(s):  
Hong Yu Qi ◽  
Hai Quan Ma ◽  
Xu Li ◽  
Xiao Guang Yang ◽  
Duo Qi Shi
Keyword(s):  
Young’S Modulus ◽  
Thermal Barrier Coatings ◽  
Bond Coat ◽  
Gas Turbines ◽  
Room Temperature ◽  
Young's Modulus ◽  
Thermal Barrier ◽  
Air Cooling ◽  
Maximum Relative Error ◽  
Barrier Coatings

Turbine vanes and blades are the most intensively loaded elements in that they are subjected to a large variety of mechanical and high temperature loads. The thermal barrier coatings (TBCs) are widely used on different hot components of gas turbines, as blades and vanes, for both, power engineering as well as aeronautical applications. Currently, two methods are used for depositing TBCs on substrate, which are plasma spray (PS) and electron beam-physical vapor deposition (EB-PVD). A typical TBCs system consists of two thin coatings, including a ceramic coating and a metallic bond coat. Despite considerable efforts, the highly desirable prediction of their life time is still a demanding task. The PS coating was focused on in this work. Firstly, the TBCs systems are multiplayer material systems. The material properties are not easily determined, such as Young’s modulus of the top-coating of TBCs. Using the resonant frequency and the composite beam theory, the Young’s modulus of APS TBCs was gotten under from room temperature to 1150°C. Then using a commercial finite-element program, the model geometry is that of a cylinder specimen. The interface region between bond coat and top coating is modeled and meshed with a sinusoidal geometry. The temperature was designed and cycled over a range from room temperature to 1050°C. The force-air-cooling was designed to form temperature gradient across the thickness of TBCs. Finally, the fatigue life of TBCs was predicated. The maximum relative error is 20.1%.

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