scholarly journals Enhancement of thermal cycling resistance of EB-PVD YSZ and CeO2 thermal barrier coatings by deposition of a Ni-Al bond coat

2018 ◽  
Author(s):  
S. A. Martynov ◽  
M. S. Kazachenok ◽  
A. R. Shugurov ◽  
A. M. Kasterov
Keyword(s):  
Thermal Cycling ◽  
Thermal Barrier Coatings ◽  
Bond Coat ◽  
Thermal Barrier ◽  
Barrier Coatings

Oxidation Behavior of Thermal Barrier Coatings on Copper Substrates

2010 ◽  
Vol 66 ◽  
pp. 74-79
Author(s):  
Jana Schloesser ◽  
Martin Bäker ◽  
Joachim Rösler ◽  
Robert Pulz
Keyword(s):  
Thermal Cycling ◽  
Thermal Barrier Coatings ◽  
Bond Coat ◽  
Thermal Protection ◽  
Rocket Engine ◽  
Copper Substrate ◽  
Thermally Grown Oxide ◽  
Substrate Material ◽  
Thermal Barrier ◽  
Barrier Coatings

In rocket engine combustion chambers, the cooling channels experience extremely high temperatures and environmental attack. Thermal protection can be provided by Thermal Barrier Coatings. Due to the need of good heat conduction, the inner combustion liner is made of copper. The performance of a standard coating system for nickel based substrates is investigated on copper substrates. Thermal cycling experiments are performed on the coated samples. Due to temperature limitations of the copper substrate material, no thermally grown oxide forms at the interface of the thermal barrier coating and the bond coat. Delamination of the coatings occurs at the interface between the substrate and the bond coat due to oxide formation of the copper at uncoated edges. In real service a totally dense coating can probably not be assured which is the reason why this failure mode is of importance. Different parameters are used for thermal cycling to understand the underlying mechanisms of delamination. Furthermore, laser heating experiments account for the high thermal gradient in real service. Pilot tests which led to a delamination of the coating at the substrate interface were performed successfully.

scholarly journals Mechanisms Controlling the Performance and Durability of Thermal Barrier Coatings

2000 ◽  
Author(s):  
Daniel R. Mumm ◽  
Anthony G. Evans
Keyword(s):  
Thermal Cycling ◽  
Thermal Barrier Coatings ◽  
Bond Coat ◽  
Large Scale ◽  
Mechanical Performance ◽  
Thermal Protection ◽  
Crack Nucleation ◽  
Ceramic Coatings ◽  
Thermal Barrier ◽  
Barrier Coatings

Abstract Thermal protection systems based on ceramic thermal barrier coatings (TBCs) are used extensively to protect hot-section components in gas turbine engines. They comprise thermally insulating ceramic coatings, deposited on an aluminum-containing intermetallic bond coat (BC) that provides oxidation protection. A thin thermally-grown oxide (TGO layer forms between the TBC and BC during cyclic thermal exposure. Each of the system constituents evolves in service and all interact during thermal cycling to control the thermo-mechanical performance of the system. Exposed to thermal cycling conditions, TBC systems are susceptible to loss of adhesion and spalling failures. Multiple failure mechanisms exist, dependent upon differing thermal histoiy and processing approach for various coating systems. Coating failure is ultimately controlled by the large residual compression in the TGO and its role in amplifying the effects of imperfections in the vicinity of the TGO. The failure occurs through a process involving crack nucleation, propagation and coalescence events. For a particular commercial system, it is found that the TGO ‘ratchets’ into the bond coat with each thermal cycle, at an array of interfacial sites. The displacements induce strains in the superposed TBC that cause it to crack. The cracks extend laterally as the TGO ratcheting process proceeds, until the cracks from neighboring sites coalesce. Once this happens, the system fails by large scale buckling. It is shown that the displacements are ‘vectored’ by a lateral component of the growth strain in the TGO. The relative roles of bond coat visco-plasticity, initial interface morphology, and phase evolution are discuss. The behavior observed for this system is compared with predictions of a ratcheting model, as well as with the behavior observed for other commercial coating systems.

Thermal Analysis and Failure Behavior of 8YSZ Thermal Barrier Coatings under Thermal Cycling Tests

2013 ◽  
Vol 441 ◽  
pp. 91-95 ◽  
Author(s):  
Guan Xiong Lu ◽  
Li Jun Hao ◽  
Fu Xing Ye
Keyword(s):  
Thermal Analysis ◽  
Thermal Cycling ◽  
Thermal Shock ◽  
Thermal Barrier Coatings ◽  
Bond Coat ◽  
Failure Behavior ◽  
Thermal Barrier ◽  
Air Cooling ◽  
Thermal Shock Test ◽  
Barrier Coatings

In this study, thermal analysis and thermal shock test of 8wt.% yttria stablized zirconia (8YSZ) thermal barrier coatings (TBCs) on low heat rejection (LHR) diesel engine have been conducted. The influence of TBCs on temperature distribution of piston was discussed by employing ANSYS codes. The thermal shock resistance test was carried out by placing the samples under flame jet heating and compressed air cooling in turn. Two kinds of thermal cycling modes with different periods were used to investigate the role of cycling frequency in coatings failure. As the frequency rose, the service life of coatings significantly decreased. The spallation of coatings happened at the interface between bond coat and substrate. The stress calculation results indicated that considerable stress caused by thermal mismatch was one of the main reasons for TBCs failure. The heat affected zone (HAZ) under the bond coat inhibited the diffusion between the bond coat and substrate. The oxide layer consisting of Mg and Al oxides under the HAZ was harmful to the bond between bond coat and substrate, which was another main reason for the spallation of coatings.

A Comparative Study of Two-Layer NiAl Bond Coat TBC and its Failure Mechanism

2007 ◽  
Vol 336-338 ◽  
pp. 1770-1772
Author(s):  
He Fei Li ◽  
Zhao Hui Zhou ◽  
Hesnawi A ◽  
Kuo Jiang ◽  
Sheng Kai Gong
Keyword(s):  
Electron Beam ◽  
Comparative Study ◽  
Thermal Cycling ◽  
Failure Mechanism ◽  
Thermal Barrier Coatings ◽  
Vapor Deposition ◽  
Bond Coat ◽  
Physical Vapor Deposition ◽  
Thermal Barrier ◽  
Barrier Coatings

Thermal barrier coatings with one-layered/ two-layered NiAl bond coat were produced by electron beam physical vapor deposition (EB-PVD). Compared to the TBC with one-layered bond coat, the TBC with two-layered bond coat improved the thermal cycling resistance significantly. The failure mechanism of the two-layer NiAl bond coat TBC was investigated in this paper.

Evolution of Photostimulated Luminescence During Thermal Cycling of Electron Beam Physical Vapor Deposited Thermal Barrier Coatings

2005 ◽  
Author(s):  
B. Jayaraj ◽  
B. Franke ◽  
S. Laxman ◽  
D. Miranda ◽  
J. Liu ◽  
...  
Keyword(s):  
Electron Beam ◽  
Thermal Cycling ◽  
Thermal Barrier Coatings ◽  
Bond Coat ◽  
Dwell Time ◽  
Life Assessment ◽  
Thermal Barrier ◽  
Photostimulated Luminescence ◽  
Barrier Coatings ◽  
Bond Coats

Thermal barrier coatings (TBCs) are widely used for thermal protection of hot section components in turbines for propulsion and power generation. Development of a robust non-destructive evaluation (NDE) technique for TBCs is essential for quality control, life assessment and health monitoring that will facilitate reliable application, efficient maintenance and prevention of catastrophic failure. In this study, degradation of TBCs was non-destructively evaluated by photostimulated luminsecence (PSLS) and microstructurally examined as a function of furnace thermal cycling carried out in air with 10-minute heat-up, 1-, and 10-hour dwell duration at 2050°F (1121°C), and 10-minute forced-air quench. TBCs examined in this study consisted of electron beam physical vapor deposited (EB-PVD) yttria-stabilized zirconia (YSZ) on grit-blasted (Ni,Pt)Al or as-coated (Ni,Pt)Al or shot-peened NiCoCrAlY bond coats and various superalloy substrates. Characteristics of subcritical-subsurface damage near the thermally grown oxide (TGO) were documented by cross-sectional scanning electron microscopy. Mechanisms of damage varied as a function of TBC type and thermal cycling dwell time, and included preferential grain boundary oxidation after ridge-induced micro-cracking, racheting and undulation of TGO/bond coat interface, internal oxidation of bond coats, and formation of Ni/Co-rich oxides. These microstructural observations are correlated to the evolution in compressive residual stress in the TGO scale determined by photostimulated luminescence shift, including stress-relief associated with subcritical cracking in the TGO scale, and stress-relaxation associated with racheting of the TGO/bond coat interface. Correlations between the microstructural development and the photostimulated luminescence from the TGO scale are discussed as a function of TBC type and thermal cycling dwell time.

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