Effect of thermal exposure on the microstructure and properties of EB-PVD gradient thermal barrier coatings

2003 ◽  
Vol 168 (1) ◽  
pp. 23-29 ◽  
Author(s):  
Hongbo Guo ◽  
Shengkai Gong ◽  
Khiam Aik Khor ◽  
Huibin Xu
Keyword(s):  
Thermal Barrier Coatings ◽  
Thermal Exposure ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
Microstructure And Properties

Improving Contact Damage Resistance of Thermal Barrier Coatings by Incorporating Buffer Layer

2009 ◽  
Vol 620-622 ◽  
pp. 319-322
Author(s):  
Sung Il Jung ◽  
Young Seok Sim ◽  
Jae Hyun Kim ◽  
Je Hyun Lee ◽  
Yeon Gil Jung ◽  
...  
Keyword(s):  
Buffer Layer ◽  
Thermal Barrier Coatings ◽  
Dwell Time ◽  
Thermal Exposure ◽  
Thermal Barrier ◽  
Lower Stress ◽  
Stress Strain ◽  
Barrier Coatings ◽  
Bond Coats ◽  
Tbc Systems

The effects of the introduction of a buffer layer between the bond and top coats on the indentation stress-strain behavior and the contact damage were investigated in air-plasma sprayed (APS) zirconia (ZrO2)–based thermal barrier coatings (TBCs). The microstructure is relatively continuous in the TBC system with the buffer layer, showing Zr, Ni, Cr, and Mg elements between the top and bond coats, whereas the Zr element suddenly disappears by passing the interface between the top and bond coats. The TBC system with the buffer layer shows less strain than that without the buffer layer in the higher stress regions above about 1.3 GPa, while both TBC systems become soft by forming the top coat in the lower stress regions compared with the substrate. The stress–strain curve in both TBC systems is dependent on the dwell time of thermal exposure condition. The TBC system with the buffer layer shows the lower stress-strain curves than that without the buffer layer in thermal cycles with the relatively short dwell time of 1 h, showing the reverse trend with the relatively long dwell time of 10 h. Subsurface damage in substrate is reduced at both indentation loads of P = 500 N and P = 2000 N by introducing the buffer layer, independent of thermal exposure. Therefore, the TBC system with the buffer layer is more efficient in protecting the substrate from contact environments than that without the buffer layer, showing cracking or delamination between the top coat and the buffer layer in the TBC system with the buffer layer.

Determination of the Structure and Chemistry of Thermally Grown Oxides in Thermal Barrier Coatings

1999 ◽  
Vol 5 (S2) ◽  
pp. 854-855
Author(s):  
M.R. Brickey ◽  
J.L. Lee
Keyword(s):  
Thermal Barrier Coatings ◽  
Nickel Aluminide ◽  
Physical Vapor Deposition ◽  
Thermal Exposure ◽  
Thermally Grown Oxide ◽  
Thermal Barrier ◽  
Engine Operation ◽  
Barrier Coatings ◽  
Combustion Gas ◽  
Thermally Grown

Thermal barrier coatings (TBCs) insulate gas turbine hot section components from the hot (∽1200 - 1450°C) combustion gas exhaust stream. An airline company can save millions of dollars per year by using TBCs to protect vital engine components and to improve fuel efficiency. TBCs typically consist of an 8 wt.% yttria-partially-stabilized zirconia (YPSZ) ceramic topcoat deposited on a platinum-nickel-aluminide (Pt-Ni-Al) bondcoat covering a nickel-based superalloy substrate. Thermal exposure during YPSZ electron beam-physical vapor deposition (EB-PVD) and engine operation promotes the formation of a thermally grown oxide (TGO) between the Pt-Ni-Al and the YPSZ layers. Stresses can develop at the Pt-Ni-Al/TGO and TGO/YPSZ interfaces due to TGO growth and thermal expansion coefficient mismatch. These stresses eventually cause spallation of the YPSZ, leaving the metallic substrate vulnerable to high temperature degradation since exhaust temperatures are often higher than the melting temperature of most nickel-based superalloys (∽1200 - 1450°C).

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.

MICROSTRUCTURAL EVOLUTION AND RESIDUAL STRESSES OF AIR-PLASMA SPRAYED THERMAL BARRIER COATINGS UNDER THERMAL EXPOSURE

2010 ◽  
Vol 17 (03) ◽  
pp. 337-343 ◽  
Author(s):  
JAE-YOUNG KWON ◽  
JAE-HYOUN KIM ◽  
SANG-YEOP LEE ◽  
YEON-GIL JUNG ◽  
HYUN CHO ◽  
...  
Keyword(s):  
Thermal Barrier Coatings ◽  
Microstructural Evolution ◽  
Thermal Exposure ◽  
Thermally Grown Oxide ◽  
Thermal Barrier ◽  
Air Plasma ◽  
Barrier Coatings ◽  
Before And After ◽  
Peak Areas ◽  
Plasma Sprayed

Microstructural evolution and fracture behavior of zirconia ( ZrO2 )-based thermal barrier coatings (TBCs) were investigated under thermal exposure. New ZrO 2 granule with 8 wt.% yttria ( Y2O3 ) with a deformed hollow morphology was developed through a spray drying process and employed to prepare TBCs. The thermal exposure tests were conducted at 1210°C with a dwell time of 100 h till 800 h. The residual stress at the interface between top coat and thermally grown oxide (TGO) layer was measured using a nanoindentation technique before and after thermal exposure. Vertical cracks on the top coat were newly formed and interlamellar cracks at the interface were enhanced after the thermal exposure of 800 h. Especially, partial delamination was observed at the interface after the thermal exposure of 800 h in TBC samples tested. The microstructural evolution in the top coat could be defined through load–displacement curves, showing a higher load or a less displacement after the thermal exposure of 800 h. The stress state was strongly dependent on the TGO geometry, resulting in the compressive stresses at the "valleys" or the "troughs," and the tensile stresses at the "crests" or peak areas, in the ranges of -500 to -75 MPa and of +168 to + 24 MPa, respectively. These stress terms incorporated with resintering during thermal exposure affected the mechanical properties such as hardness and elastic modulus of the top coat.

Microstructural Evolution and Mechanical Properties of Vertical-Cracked Thermal Barrier Coatings in Thermal Exposure

2012 ◽  
Vol 512-515 ◽  
pp. 1040-1044 ◽  
Author(s):  
Zhe Lu ◽  
Sang Won Myoung ◽  
Tae Sik Jang ◽  
Kang Hyeon Lee ◽  
Je Hyun Lee ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Thermal Stability ◽  
Thermal Barrier Coatings ◽  
Total Porosity ◽  
Thermal Exposure ◽  
Thermal Barrier ◽  
Air Plasma ◽  
Barrier Coatings ◽  
Plasma Sprayed ◽  
Intrinsic Feature

The effects of intrinsic feature of feedstock in air plasma-sprayed (APS) coatings on the microstructure and mechanical properties of vertical-cracked thermal barrier coatings (TBCs) were investigated in thermal exposure. The microstructure after the thermal exposure for 400 h is densified, while after the thermal exposure for 800 h various defects such as interlamellar cracks and the vertical and horizontal cracks are newly developed, even though the total porosity is decreased. The microstructure of the TBC prepared with 204 C-NS is more porous than that of the TBC with 204NS, showing higher mechanical properties and better thermal stability in the TBC with 204 NS.

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