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.

Effects of Powder Morphology, Microstructure, and Residual Stresses on Thermal Barrier Coating Thermal Shock Performance

1996 ◽  
Author(s):  
J. Wigren ◽  
J.-F. de Vries ◽  
D. Greving
Keyword(s):  
Residual Stresses ◽  
Thermal Shock ◽  
Thermal Barrier Coating ◽  
Thermal Barrier Coatings ◽  
Gas Turbines ◽  
Thermal Barrier ◽  
Spray Parameters ◽  
Powder Morphology ◽  
Barrier Coatings ◽  
Barrier Coating

Abstract Thermal barrier coatings are used in the aerospace industry for thermal insulation in hot sections of gas turbines. Improved coating reliability is a common goal among jet engine designers. In-service failures, such as coating cracking and spallation, result in decreased engine performance and costly maintenance time. A research program was conducted to evaluate residual stresses, microstructure, and thermal shock life of thermal barrier coatings produced from different powder types and spray parameters. Sixteen coatings were ranked according to their performance relative to the other coatings in each evaluation category. Comparisons of residual stresses, powder morphology, and microstructure to thermal shock life indicate a strong correlation to thermal barrier coating performance. Results from these evaluations will aid in the selection of an optimum thermal barrier coating system for turbine engine applications.

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.

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.

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.

Influence of Top Coat and Bond Coat Pre-Oxidation on the Corrosion Resistance of Thermal Barrier Coatings in the Presence of SO2

2018 ◽  
Author(s):  
Krishna Praveen Jonnalagadda ◽  
Kang Yuan ◽  
Xin-Hai Li ◽  
Xiaojuan Ji ◽  
Yueguang Yu ◽  
...  
Keyword(s):  
Thermal Barrier Coatings ◽  
Bond Coat ◽  
Gas Turbines ◽  
Corrosion Damage ◽  
Thermal Barrier ◽  
Low Grade ◽  
Barrier Coatings ◽  
Corrosion Tests ◽  
Single Side ◽  
The Difference

Thermal barrier coatings (TBCs) degradation due to corrosion is one of the commonly observed failure types in land-based gas turbines due to the usage of low grade fuels. Sulfur in its gaseous form, as SO2, can attack the TBC system and result in the degradation of both the coating and the turbine component. The present study aims to understand the difference in the corrosion induced damage caused by SO2 gas mixture in different coating architectures. Corrosion tests were conducted at 780 °C in a tube furnace for a period of 168h. The inlet test gas had a composition of 1SO2-0.1CO-20CO2-N2 (bal.) in vol. %. The coating architectures consisted of 1) an overlay coating, 2) a single-side bond coat TBC, 3) an all-side bond coat TBC, 4) an all-side bond coat TBC subjected to pre-oxidation prior to the corrosion tests. The results from the corrosion tests showed that the damage was the most severe for the overlay followed by single-side bond coat TBC. Between the other two systems, the TBC subjected to pre-oxidation had relatively lower corrosion damage. The corrosion damage started from the edges for the overlay and single-side bond coat TBC and as well as through the penetration of the gas through the coating. For the coatings with bond coat on all sides, the edge damage appeared to be considerably reduced and the damage is predominantly through the gas infiltration.

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.

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.

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).

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