Thermal Cycling Fatigue of Thermal Barrier Coatings - Rig and Experiment Design

2014 ◽  
Vol 891-892 ◽  
pp. 641-646
Author(s):  
Robert Eriksson ◽  
Hakan Brodin ◽  
Sten Johansson ◽  
Lars Östergren ◽  
Xin Hai Li
Keyword(s):  
High Temperature ◽  
Thermal Cycling ◽  
Cooling Rate ◽  
Thermal Barrier Coatings ◽  
Gas Turbines ◽  
Coefficient Of Thermal Expansion ◽  
Thermal Barrier ◽  
Short Side ◽  
Metallic Component ◽  
Barrier Coatings

Ceramic thermal barrier coatings are used for thermal insulation in gas turbines to protect metallic components from high-temperature degradation. The ceramic coating may, due to its different coefficient of thermal expansion, crack and spall off the metallic component, thus rendering the component unprotected against high-temperature. Thermal cycling rigs of various designs are used to evaluate the durability of thermal barrier coatings. The present paper reports the result from a round robin test including three thermal cycling rigs at different locations. To better understand the influence of rig design on the thermal cyclic lives of thermal barrier coatings, some test parameters, such as the material of the specimen table and the cooling rate, were varied in one of the rigs. Furthermore, two different specimen geometries, rectangular and disc-shaped, were tested. The specimen table material was found to greatly influence the cooling rate of the specimens, more so than variations in the cooling airflow. The rectangular specimens were found to be more sensitive to test setup than the disc-shaped specimens; under certain conditions, the rectangular specimens could be made to fracture from the long side, rather than the short side of the specimen edge, which shortened the thermal cyclic life of the coatings.

Bond coating issues in thermal barrier coatings for industrial gas turbines

2005 ◽  
Vol 219 (2) ◽  
pp. 101-107 ◽  
Author(s):  
I. G. Wright ◽  
B. A. Pint
Keyword(s):  
High Temperature ◽  
Oxide Layer ◽  
Thermal Barrier Coatings ◽  
Gas Turbines ◽  
Metallic Surface ◽  
Thermal Barrier ◽  
Protective Oxide ◽  
Barrier Coatings ◽  
Bond Coating ◽  
Industrial Gas Turbines

Thermal barrier coatings are intended to work in conjunction with internal cooling schemes to reduce the metal temperature of critical hot gas path components in gas turbine engines. The thermal resistance is typically provided by a 100-250 μm thick layer of ceramic (most usually zirconia stabilized with an addition of 7–8 wt% of yttria), and this is deposited on to an approximately 50 μ thick, metallic bond coating that is intended to anchor the ceramic to the metallic surface, to provide some degree of mechanical compliance, and to act as a reservoir of protective scale-forming elements (Al) to protect the underlying superalloy from high-temperature corrosion. A feature of importance to the durability of thermal barrier coatings is the early establishment of a continuous, protective oxide layer (preferably α-alumina) at the bond coating—ceramic interface. Because zirconia is permeable to oxygen, this oxide layer continues to grow during service. Some superalloys are inherently resistant to high-temperature oxidation, so a separate bond coating may not be needed in those cases. Thermal barrier coatings have been in service in aeroengines for a number of years, and the use of this technology for increasing the durability and/or efficiency of industrial gas turbines is currently of significant interest. The data presented were taken from an investigation of routes to optimize bond coating performance, and the focus of the paper is on the influences of reactive elements and Pt on the oxidation behaviour of NiAl-based alloys determined in studies using cast versions of bond coating compositions.

The Effect of Laser Glazing on High Temperature Oxidation Resistance of Thermal Barrier Coatings

2012 ◽  
Vol 433-440 ◽  
pp. 315-318
Author(s):  
Seyid Fehmi Diltemiz ◽  
Melih Cemal Kushan
Keyword(s):  
High Temperature ◽  
Oxidation Resistance ◽  
Thermal Barrier Coatings ◽  
Gas Turbines ◽  
High Temperature Oxidation ◽  
304 Stainless Steel ◽  
Thermal Barrier ◽  
Laser Glazing ◽  
Temperature Oxidation ◽  
Barrier Coatings

Thermal barrier coatings (TBCs) have been widely used by aero and land based gas turbines to protect hot section parts from oxidation and thermal loads. These coatings are generally consisting of multiple layers of coating (usually two) with each layer having a specific function. TBCs are generally deposited with air plasma spray (APS) or electron beam physical vapor deposition (EB-PVD) techniques. In this paper plasma sprayed TBCs were deposited on to 304 stainless steel substrates then ceramic surfaces were glazing with Nd-YAG laser. Metallographic examinations were applied to the samples to investigate microstructural changes in glazed ceramic layer. Both glazed and as-coated samples were subjected to oxidation tests to measure the high temperature oxidation resistance. The tests showed that, laser glazing is beneficial to oxidation resistance of TBCs. This improvement is attributed to sintering of zirconia layer which act as oxygen barrier and formed during glazing process.

Fundamental Coating Development Study to Improve the Isothermal Oxidation Resistance and Thermal Cycle Durability of Thermal Barrier Coatings

2006 ◽  
Vol 522-523 ◽  
pp. 247-254 ◽  
Author(s):  
Taiji Torigoe ◽  
Hidetaka Oguma ◽  
Ikuo Okada ◽  
Guo Chun Xu ◽  
Kazuhisa Fujita ◽  
...  
Keyword(s):  
High Temperature ◽  
Thermal Barrier Coatings ◽  
Gas Turbines ◽  
Turbine Blades ◽  
Atmospheric Plasma ◽  
Zirconia Ceramic ◽  
Thermal Barrier ◽  
Temperature Oxidation ◽  
Barrier Coatings ◽  
Oxidation Properties

Thermal barrier coatings(TBCs) are used in high temperature gas turbines to reduce the surface temperature of cooled metal parts such as turbine blades[1]. TBC consist of a bondcoat (e.g. MCrAlY where M is Co, Ni, CoNi, etc.) and a partially stabilized zirconia ceramic topcoat. Usually, the MCrAlY bondcoat is applied by LPPS (low pressure plasma spray) or HVOF(high velocity oxi-fuel spray). The topcoat is applied by APS (atmospheric plasma splay) or EB-PVD (electron beam-physical vapor deposition). High temperature oxidation properties, thermal barrier properties and durability of TBC are very important to increase the reliability in high temperature service. In this study, new TBC has been investigated. The new TBC consists of a two-layered bondcoat (LPPS-MCrAlY plus dense PVD overlay MCrAlY) and the EB-PVD type YSZ columnar structure topcoat. As a result of evaluation tests, it was confirmed that the new TBC had better oxidation properties and durability than a conventional TBC system.

High-Temperature Performance of Self-Healing SiC-YSZ Thermal Barrier Coatings Deposited by Using Various Plasma Spray Concepts

2021 ◽  
Author(s):  
Mohammad Hassanzadeh ◽  
Paweł Sokołowski ◽  
Radek Musalek ◽  
Jan Medricky ◽  
Stefan Csaki
Keyword(s):  
High Temperature ◽  
Thermal Barrier Coatings ◽  
Plasma Spray ◽  
Gas Turbines ◽  
Isothermal Oxidation ◽  
Atmospheric Plasma ◽  
Flash Method ◽  
Thermal Barrier ◽  
Self Healing ◽  
Barrier Coatings

Abstract In this study; a novel self-healing concept is considered in order to increase the lifetime of thermal barrier coatings (TBCs) in modern gas turbines. For that purpose; SiC healing particles were introduced to conventional 8YSZ topcoats by using various plasma spray concepts; i.e.; composite or multilayered coatings. All topcoats were sprayed by SG-100 plasma torch on previously deposited NiCrAlY bondcoats produced by conventional atmospheric plasma spraying. Coatings were subjected to thermal conductivity measurements by laser flash method up to 1000°C; isothermal oxidation testing up to 200h at 1100°C and finally thermal cyclic fatigue (TCF) lifetime testing at 1100°C. Microstructural coating evaluation was performed by scanning electronic microscope (SEM); in the as-produced and post high-temperature tested states. This was done to analyze the self-healing phenomena and its influence on the hightemperature performance of the newly developed TBCs.

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.

YTTRIA-STABILIZED ZIRCONIA THERMAL BARRIER COATINGS — A REVIEW

2006 ◽  
Vol 13 (05) ◽  
pp. 535-544 ◽  
Author(s):  
L. B. CHEN
Keyword(s):  
High Temperature ◽  
Thermal Barrier Coatings ◽  
Coefficient Of Thermal Expansion ◽  
Yttria Stabilized Zirconia ◽  
Thermal Barrier ◽  
Stabilized Zirconia ◽  
Barrier Coatings ◽  
Recent Developments ◽  
Structural Parts ◽  
Power Generation Systems

Thermal barrier coatings (TBCs), which protect metallic components from high-temperature environments, have been widely applied to the fields of high-temperature and corrosion-resistant structural parts such as gas turbine engines, diesel engines, and power generation systems. Yttria-stabilized zirconia (YSZ) is one of the most widely used materials for TBCs owing to its excellent shock resistance, low-thermal conductivity, and relatively high coefficient of thermal expansion. In this paper the properties of YSZ and the recent developments of YSZ-TBCs are reviewed. The failure mechanism of YSZ-TBCs and corresponding methods for lengthening the lifetime of YSZ-TBCs are discussed. The advantages of graded thermal barrier coatings and the problems in processing are elucidated.

Modelling Failures of Thermal Barrier Coatings

2007 ◽  
Vol 333 ◽  
pp. 155-166 ◽  
Author(s):  
Anette M. Karlsson
Keyword(s):  
High Temperature ◽  
Thermal Barrier Coatings ◽  
Gas Turbines ◽  
Metal Substrate ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Design Engineers ◽  
Material Physics ◽  
Temperature Exposure ◽  
And Diffusion

Thermal barrier coatings are commonly used in high temperature parts of gas turbines, to protect the underlying metal substrate from deterioration during high temperature exposure. Unfortunately, the coatings fail prematurely, preventing the design engineers to fully utilize their implementation. Due to the complexity of the coatings, there are many challenges involved with developing failure hypotheses for the failures. This paper reviews some aspects of the current stateof- the-art on modeling failures of thermal barrier coatings, focusing on mechanics based models (such as finite element simulations) where the material physics is incorporated (such as oxidation and diffusion).

scholarly journals Characterization of Fatigue Mechanisms of Thermal Barrier Coatings by a Novel Laser-Based Test

1998 ◽  
Author(s):  
Uwe Rettig ◽  
Ulrich Bast ◽  
Dinorah Steiner ◽  
Matthias Oechsner
Keyword(s):  
High Temperature ◽  
Thermal Barrier Coatings ◽  
Gas Turbines ◽  
Fatigue Behavior ◽  
Temperature Gradients ◽  
Stress Fields ◽  
Thermal Barrier ◽  
Data Set ◽  
Barrier Coatings

The use of high performance ceramic thermal barrier coatings in stationary gas turbines requires fundamental knowledge of their fatigue behavior under high temperature gradients and thermal cycling. An experimental method based on rapid laser heating complemented with finite-element calculations was developed in order to identify the major damage mechanisms and to obtain a data set for reliability assessment of thermal barrier coatings for temperature and stress fields similar to gas turbine conditions. The observed failures are strongly related to the pretreatment procedures such as annealing under high temperature gradients and isothermal long-term oxidation. The vertical crack patterns observed close to the top surface of the Zirconia coating are generated at the moment of rapid cooling. These cracks are induced by high biaxial tensile stresses caused by the temperature gradient and the stress reversion after relaxation of compressive stresses at high temperatures. The long-term fatigue behavior is decisively determined by two processes: (i) The porous Zirconia loses its damage tolerant properties by densification. (ii) The growth of an oxide layer at the bond coat degrades adhesion and produces localized stress fields at the interface. Cyclic loads increase the length of existing in-plane cracks and delaminations rather than enlarging their number. Misfit of the crack flanks and wedge effects are the driving forces for continued crack propagation. These experimental results are discussed in terms of fracture mechanics.

Thermo-Mechanical Study of the Role of Gd2Zr2O7 (GZ) in Improving Life of YSZ and GZ Double Layered Thermal Barrier Coatings

2012 ◽  
Author(s):  
Patrick F. Mensah ◽  
Ravinder Diwan ◽  
Swamy Nandikolla ◽  
Omotola Coker ◽  
Purush Sahoo
Keyword(s):  
Thermal Cycling ◽  
Elastic Properties ◽  
Thermal Barrier Coatings ◽  
Coefficient Of Thermal Expansion ◽  
Atmospheric Plasma ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Mechanical Study ◽  
Ysz Coating ◽  
Cte Mismatch

Thermo-mechanical properties and thermal cycling behavior of gadolinium zirconate Gd2Zr2O7 (GZ) based thermal barrier coatings (TBCs) was investigated in this study in comparison to conventional yttria-stabilized zirconia (YSZ) coatings. This paper presents results focusing on coefficient of thermal expansion (CTE) measurements, thermal cycling tests, measured elastic properties and porosity of the multilayered GZ/YSZ TBCs deposited by atmospheric plasma spraying (APS) on an Inconel 738 (IN738) superalloy substrate. SEM microstructural images of failed TBC specimens are also presented. Samples of different double layer combinations with one layer being either 100% YSZ or 100% GZ and the second containing varying amounts of the two compounds were prepared to determine optimum combination that maintains good insulating properties while reducing the CTE mismatch between the TBC layers. The temperature range of the tests was 25°C to 1300°C. The samples are processed by APS on (Ø −12.7 mm, thickness 3 mm) IN738. Using a dilatometer, CTEs of the as sprayed top coat (TC) combinations are measured and compared. The elastic properties are measured using a Hysitron nanoindenter. Results showed that the 10%GZ/ 90%YSZ+ 100YSZ double layered structure was the best among the tested GZ based TBCs and the delamination of GZ/YSZ coating first initiated in the GZ layer close to the interface of GZ and YSZ layers, which was mainly caused by the sintering effect of the GZ layer.

Characterization of Fatigue Mechanisms of Thermal Barrier Coatings by a Novel Laser-Based Test

1999 ◽  
Vol 121 (2) ◽  
pp. 259-264 ◽  
Author(s):  
U. Rettig ◽  
U. Bast ◽  
D. Steiner ◽  
M. Oechsner
Keyword(s):  
High Temperature ◽  
Thermal Barrier Coatings ◽  
Gas Turbines ◽  
Fatigue Behavior ◽  
Temperature Gradients ◽  
Stress Fields ◽  
Thermal Barrier ◽  
Data Set ◽  
Barrier Coatings

The use of high performance ceramic thermal barrier coatings in stationary gas turbines requires fundamental knowledge of their fatigue behavior under high temperature gradients and thermal cycling. An experimental method based on rapid laser heating complemented with finite-element calculations was developed in order to identify the major damage mechanisms and to obtain a data set for reliability assessment of thermal barrier coatings for temperature and stress fields similar to gas turbine conditions. The observed failures are strongly related to the pretreatment procedures such as annealing under high temperature gradients and isothermal long-term oxidation. The vertical crack patterns observed closed to the top surface of the Zirconia coating are generated at the moment of rapid cooling. These cracks are induced by high biaxial tensile stresses caused by the temperature gradient and the stress reversion after relaxation of compressive stresses at high temperatures. The long-term fatigue behavior is decisively determined by two processes: (1) the porous Zirconia loses its damage tolerant properties by densification, and (2) the growth of an oxide layer at the bond coat degrades adhesion and produces localized stress fields at the interface. Cyclic loads increase the length of existing in-plane cracks and delaminations rather than enlarging their number. Misfit of the crack flanks and wedge effects are the driving forces for continued crack propagation. These experimental results are discussed in terms of fracture mechanics.

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