Critical Weak Points of Atmospheric Plasma Sprayed Thermal Barrier Coatings

2014 ◽  
Vol 782 ◽  
pp. 567-572 ◽  
Author(s):  
David Jech ◽  
Ladislav Čelko ◽  
Martin Juliš ◽  
Lenka Klakurková ◽  
Karel Slámečka ◽  
...  
Keyword(s):  
Thermal Barrier Coatings ◽  
Bond Coat ◽  
Structural Changes ◽  
Thermal Exposure ◽  
Atmospheric Plasma ◽  
Thermal Barrier ◽  
Ambient Atmosphere ◽  
Polycrystalline Nickel ◽  
Barrier Coatings ◽  
Weak Points

The 8 wt. % yttria stabilized zirconia top coat (TC) and the CoNiCrAlY bond coat (BC) were sprayed onto the surface of newly developed fine-grained cast polycrystalline nickel-based superalloy Inconel 713LC by means of atmospheric plasma spraying (APS). As-prepared samples were isothermally exposed at the temperature of 1050 °C for 200 hours in an ambient atmosphere. Structural changes in the thermal barrier coatings (TBC) system after thermal exposure were studied by means of scanning electron microscope equipped with an energy dispersive microanalyzer. Critical weak points were identified on both the substrate-bond coat and bond coat-top coat interfaces.

scholarly journals Thermal durability of thermal barrier coatings with layered bond coat in cyclic thermal exposure

2014 ◽  
Vol 122 (1432) ◽  
pp. 982-988 ◽  
Author(s):  
Min-Sik KIM ◽  
Sang-Won MYOUNG ◽  
Zhe LU ◽  
Je-Hyun LEE ◽  
Yeon-Gil JUNG ◽  
...  
Keyword(s):  
Thermal Barrier Coatings ◽  
Bond Coat ◽  
Thermal Exposure ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Thermal Durability

scholarly journals Thermal Stability of YSZ Thick Thermal Barrier Coatings Deposited by Suspension and Atmospheric Plasma Spraying

Crystals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 984
Author(s):  
Shiqian Tao ◽  
Jiasheng Yang ◽  
Minglong Zhai ◽  
Fang Shao ◽  
Xinghua Zhong ◽  
...  
Keyword(s):  
Plasma Spraying ◽  
Thermal Barrier Coatings ◽  
Thermal Aging ◽  
Thermal Exposure ◽  
Atmospheric Plasma Spraying ◽  
Atmospheric Plasma ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Aps Coatings ◽  
Steel Substrates

Two types of segmentation-crack structured yttria-stabilized zirconia (YSZ) thick thermal barrier coatings (>500 μm, TTBCs) were deposited onto the stainless steel substrates using atmospheric plasma spraying (APS) and suspension plasma spraying (SPS) process, respectively. In this work, thermal aging behaviors, such as the microstructures, phase compositions, grain growth, and mechanical properties of APS TTBCs and SPS TTBCs, were systematically investigated. Results showed that both as-sprayed TTBCs exhibited a typical segmentation-crack structure in the through-thickness direction. APS coatings mainly comprised of larger columnar crystals, while a large number of smaller equiaxed grains existed in SPS coatings. Both of the coatings underwent tetragonal-monoclinic phase transformation after 155 °C/40 h heat treatment. The poorer phase stability of SPS TTBCs may have a connection with smaller grain size. Thermal-aged APS and SPS coatings exhibited a significant increase in H and E values with the rising of thermal aging temperature, and for the samples that thermal aged at 1550 °C, the H and E values increased sharply during initial stage then decreased after 80 h due to the phase decomposition. The segmented APS coatings had weak bonding between the lamellaes during thermal exposure, which caused the mean Vickers hardness value of APS TTBCs to be much lower than that of SPS TTBCs.

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.

scholarly journals Oxidation Behavior of the Monolayered La2Zr2O7, Composite La2Zr2O7 + 8YSZ, and Double-Ceramic Layered La2Zr2O7/La2Zr2O7 + 8YSZ/8YSZ Thermal Barrier Coatings

Materials ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3242 ◽  
Author(s):  
Anna Jasik ◽  
Grzegorz Moskal ◽  
Marta Mikuśkiewicz ◽  
Agnieszka Tomaszewska ◽  
Sebastian Jucha ◽  
...  
Keyword(s):  
Thermal Barrier Coatings ◽  
Bond Coat ◽  
Microstructural Characterization ◽  
Thermally Grown Oxide ◽  
Atmospheric Plasma ◽  
Ceramic Layer ◽  
Thermal Barrier ◽  
Equal Weight ◽  
Barrier Coatings

The degradation process of thermal barrier coatings (TBCs) such as monolayered La2Zr2O7, composite 50% La2Zr2O7 + 50% 8YSZ, and double-ceramic layer (DCL) La2Zr2O7/50% La2Zr2O7 + 50% 8YSZ/8YSZ was investigated. Coatings were deposited using the atmospheric plasma spraying (APS) process (ceramic layer and bond-coat) on the Ni-based superalloy substrate with Ni-22Cr-10Al-1Y bond-coat. The thickness of the ceramic top-coats in all cases were 300 µm. In the case of La2Zr2O7/8YSZ, the internal sublayer was built from 8YSZ powder whereas the outer from La2Zr2O7. Between both sublayers’ “composite” a 50% La2Zr2O7 + 50% 8YSZ zone was present. The “composite” 50% La2Zr2O7 + 50% 8YSZ TBC system was sprayed from two different feedstock powders with equal weight ratios. In the first part of the investigation, the microstructural characterization of the TBCs was presented. The main goals were related to the characterization of the degradation processes in different TBC systems with special emphasis on the phenomenon in the thermally grown oxide (TGO) zone related to oxidation, and the phenomenon related to phase stability in ceramic top-coats as related to temperature influence. The oxidation test was carried out in air at 1100 °C for 500 h. In the second step of the investigation, the numerical simulation of the monolayered TBC 8YSZ and La2Zr2O7 systems was analyzed from the stress distribution point of view. Additionally, the two-layered TBC coating of the DCL type was also analyzed.

scholarly journals Thermal Stability of Plasma-Sprayed Thick Thermal Barrier Coatings Using Triplex ProTM-200 Torch

Coatings ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 894 ◽  
Author(s):  
Shiqian Tao ◽  
Jiasheng Yang ◽  
Wei Li ◽  
Fang Shao ◽  
Xinghua Zhong ◽  
...  
Keyword(s):  
Grain Growth ◽  
Thermal Barrier Coatings ◽  
Vickers Hardness ◽  
Engineering Application ◽  
Hardness Test ◽  
Thermal Exposure ◽  
Atmospheric Plasma ◽  
Thermal Barrier ◽  
Free Standing ◽  
Barrier Coatings

Segmentation-crack structured yttria-stabilized zirconia (YSZ) thermal barrier coatings (TBCs) were deposited by atmospheric plasma spraying (APS) using a Triplex Pro™-200 gun. In this work, free-standing coating specimens (~700 μm) were isothermally heat-treated in air from 1200 to 1600 °C for 24 h and at 1550 °C for 20 to 100 h, respectively. The thermal aging behaviors such as microstructures, phase compositions, grain growth and mechanical properties were characterized via scanning electron microscopy (SEM), X-ray diffraction (XRD), electron backscatter diffraction (EBSD) and a Vickers hardness test. The results indicated that the as-sprayed coatings mainly consisted of metastable tetragonal (t′-YSZ) phase, but the t′-YSZ gradually partitioned into equilibrium tetragonal (t-YSZ) and cubic (c-YSZ) phases due to yttrium diffusion during thermal exposure, and with an improvement in temperature, the c-YSZ may retain or transform into another yttrium-rich tetragonal (t″-YSZ) phase. The transformation of t-YSZ to monoclinic phase (m-YSZ) has occurred after 1550 °C/40 h heat treatment, and the content of the m-YSZ phase increased with the prolongation of the thermal exposure time. The variations of Vickers hardness have a correlation with pores healing and grain growth, which might be attributed to the coating sintering and m-YSZ phase formation. Furthermore, the growth pattern of the grains was investigated in detail. In service, cracks and pores proceeded along the grain boundaries, especially surrounding the small grains. It is conducive to the engineering application of TBCs fabricated with the Triplex Pro™-200 gun.

scholarly journals Isothermal Oxidation Behavior of Gadolinium Zirconate (Gd2Zr2O7) Thermal Barrier Coatings (TBCs) produced by Electron Beam Physical Vapor Deposition (EB-PVD) technique

2018 ◽  
Vol 16 (1) ◽  
pp. 986-991 ◽  
Author(s):  
Kadir Mert Doleker ◽  
Yasin Ozgurluk ◽  
Hayrettin Ahlatci ◽  
Abdullah Cahit Karaoglanli
Keyword(s):  
Electron Beam ◽  
Thermal Barrier Coatings ◽  
Vapor Deposition ◽  
Bond Coat ◽  
Physical Vapor Deposition ◽  
Isothermal Oxidation ◽  
Atmospheric Plasma ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
X Ray

AbstractThermal Barrier Coatings (TBCs) provide thermal insulation for gas turbine components operating at high temperatures. Generally, TBCs were produced on a MCrAlY bond coat with 7-8% Yttria Stabilized Zirconia (YSZ) using Atmospheric Plasma Spray (APS) technique. In this study, Inconel 718 substrate material was coated with CoNiCrAlY bond coat using high velocity oxygen fuel (HVOF) technique. Afterward, Gd2Zr2O7 was deposited on samples using Electron Beam Physical Vapor Deposition (EB-PVD) technique. Produced TBCs were exposed to isothermal oxidation tests at 1000°C for 8 h, 24 h, 50 h and 100 h in muffle furnace. Scanning electron microscopy-energy distribution X-ray (SEM-EDX) spectroscopy was used to investigate thermally grown oxide (TGO) layer and TGO growth behavior of TBCs. In addition, X-ray Diffractometer (XRD) analysis was performed to TBCs to understand whether phase transformation occurs or not before and after oxidation.

Depletion Model of Aluminum in Bond Coat for Plasma-Sprayed Thermal Barrier Coatings

2009 ◽  
Vol 75 ◽  
pp. 31-35 ◽  
Author(s):  
Chang Che ◽  
G.Q. Wu ◽  
Hong Yu Qi ◽  
Z. Huang ◽  
Xiao Guang Yang
Keyword(s):  
Mathematical Model ◽  
Thermal Barrier Coating ◽  
Thermal Barrier Coatings ◽  
Bond Coat ◽  
Thermal Exposure ◽  
Thermal Barrier ◽  
Air Plasma ◽  
Barrier Coatings ◽  
Barrier Coating ◽  
Plasma Sprayed

The aluminum depletion of NiCrAlY bond coat in an air-plasma-sprayed thermal barrier coating (TBC) has been studied by experimental and simulative approaches. Upon thermal exposure, Al depletion regions were observed. The depletion of aluminum is resulting from Al diffusion towards the surface of bond coat and into substrate. A mathematical model of Al depletion was presented. The model is able to explain the observed results in a qualitative way and has been shown that Al depletes within the bond coat by diffusion.

THERMAL SHOCK BEHAVIOR OF AIR PLASMA SPRAYED CoNiCrAlY/YSZ THERMAL BARRIER COATINGS

2014 ◽  
Vol 21 (05) ◽  
pp. 1450069 ◽  
Author(s):  
ZI WEI LIU ◽  
WEI WU ◽  
JIA JIE HUA ◽  
CHU CHENG LIN ◽  
XUE BIN ZHENG ◽  
...  
Keyword(s):  
Thermal Shock ◽  
Thermal Barrier Coatings ◽  
Thermal Shock Resistance ◽  
Structural Changes ◽  
Cold Water ◽  
Atmospheric Plasma ◽  
Thermal Barrier ◽  
Air Plasma ◽  
Barrier Coatings ◽  
Shock Resistance

The structural changes and failure mechanism of thermal barrier coatings (TBCs) during thermal shock cycling were investigated. TBCs consisting of CoNiCrAlY bond coat and partially yttria-stabilized zirconia (YSZ) top coat were deposited by atmospheric plasma spraying (APS) on a nickel-based alloy substrate and its thermal shock resistance performance was evaluated. TBCs were heated at 1100°C for 15 min followed by cold water quenching to ambient temperature. Microstructural evaluation and elemental analysis of TBCs were performed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), respectively. The crack features of YSZ coatings in TBCs during thermal shock cycling, including those of horizontal (parallel to the substrate) and vertical cracks (perpendicular to the substrate), were particularly investigated by means of SEM and image analysis. Results show that horizontal and vertical cracks have different influences on the thermal shock resistance of the coatings. Horizontal cracks that occur at the interface of YSZ and thermally growth oxidation (TGO) cause partial or large-area spalling of coatings. When vertical and horizontal cracks encounter, network segments are formed which lead to partial spalling of the coatings.

Microstructure of Thermal Barrier Coatings (TBC's) Obtained by Using Plasma Spraying and VPA Methods

2012 ◽  
Vol 706-709 ◽  
pp. 2412-2417 ◽  
Author(s):  
Marek Góral ◽  
Stanislaw Dudek ◽  
Ryszard Filip ◽  
Jan Sieniawski
Keyword(s):  
Plasma Spraying ◽  
Thermal Barrier Coatings ◽  
Bond Coat ◽  
Nickel Superalloy ◽  
Atmospheric Plasma ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Bond Coats ◽  
Pack Aluminizing ◽  
Plasma Sprayed

Thermal Barrier Coatings are the main type of coatings used for protecting turbine blade surfaces and the surface of modern jet engines combustion chamber parts. Depending on the type of engine element, the coatings are produced as plasma-sprayed MeCrAlY bond-coats with a ceramic outer layer or as Pt-modified aluminide coatings with a ceramic EB-PVD-deposited layer. Currently, research is being conducted on the deposition of a new type of coatings consisting of bond-coats with mulitlayer structure. In the article, the results of the study on the obtainment of TBC's with multilayer structure are presented. To obtain the metallic bond-coat, the process of atmospheric plasma spraying and the out of pack aluminizing (VPA) method were combined. The coatings were deposited on the surface of Rene 80 nickel superalloy. The first layer of the coating was a plasma-sprayed MCrAlY bond-coat, on which a diffusion aluminide layer was deposited with out of pack method. On the bond-coat, a standard ceramic zirconium oxide (ZrO2*20Y2O3) layer was deposited. The microstructure analysis, was conducted, using light and SEM microscopy. The phase and chemical composition analyses were done using EDS and XRD methods.

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.

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