Effect of Yb2SiO5 Ceramic Layer Thickness on the Thermal Cycling Life of Yb2SiO5⁄LaMgAl11O19 Coating Deposited on C⁄SiC Composites

2013 ◽  
Vol 537 ◽  
pp. 36-41 ◽  
Author(s):  
Ying Wang ◽  
Bing Lin Zou ◽  
Xi Zhi Fan ◽  
Xue Qiang Cao
Keyword(s):  
Thermal Expansion ◽  
High Temperature ◽  
Thermal Cycling ◽  
Layer Thickness ◽  
Chemical Stability ◽  
Influencing Mechanism ◽  
Expansion Behavior ◽  
Sic Composites ◽  
Plasma Sprayed ◽  
Cycling Life

C⁄SiC composites were plasma sprayed with Yb2SiO5⁄LaMgAl11O19 (LMA) coatings with varying Yb2SiO5 layer thickness. The effect of Yb2SiO5 layer thickness on the thermal cycling life of the Yb2SiO5LMA coatings was investigated. The results showed that the thermal cycling life is significantly dependent on the Yb2SiO5 layer thickness. It decreased from 130 cycles to 35 cycles as Yb2SiO5 layer thickness increased from 50 µm to 100 µm. Further increasing Yb2SiO5 layer thickness to 200 µm made it decrease to 2 cycles. The influencing mechanism of Yb2SiO5 layer thickness for the thermal cycling life was clarified based on the thermal expansion behavior, the chemical stability at high temperature and the microstructure analysis.

scholarly journals LC/8YSZ TBCs Thermal Cycling Life and Failure Mechanism under Extreme Temperature Gradients

Coatings ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1051
Author(s):  
Kun Liu ◽  
Xi Chen ◽  
Kangping Du ◽  
Yu Wang ◽  
Jinguang Du ◽  
...  
Keyword(s):  
High Temperature ◽  
Surface Temperature ◽  
Thermal Cycling ◽  
Thermal Shock ◽  
Failure Mechanism ◽  
Extreme Temperature ◽  
Temperature Gradients ◽  
Accelerated Life Test ◽  
Ceramic Layer ◽  
Cycling Life

The purpose of this paper is to study the thermal shock resistance and failure mechanism of La2Ce2O7/8YSZ double-ceramic-layer thermal barrier coatings (LC/8YSZ DCL TBCs) under extreme temperature gradients. At high surface temperatures, thermal shock and infrared temperature measuring modules were used to determine the thermal cycling life and insulation temperature of LC/8YSZ DCL TBCs under extreme temperature gradients by an oxygen–acetylene gas flame testing machine. A viscoelastic model was used to obtain the stress and strain law of solid phase sintering of a coating system using the finite element method. Results and Conclusion: (1) Thermal cycling life was affected by the surface temperature of LC/8YSZ DCL TBCs and decreased sharply with the increase of surface temperature. (2) The LC ceramic surface of the failure coating was sintered, and the higher the temperature, the faster the sintering process. (3) Accelerated life test results showed that high temperature thermal cycling life is not only related to thermal fatigue of ceramic layer, but is also related to the sintering degree of the coating. (4) Although the high temperature thermal stress had great influence on the coating, great sintering stress was produced with sintering of the LC ceramic layer, which is the main cause of LC/8YSZ DCL TBC failure. The above results indicate that for new TBC ceramic materials, especially those for engines above class F, their sinterability should be fully considered. Sintering affects the thermal shock properties at high temperature. Our research results can provide reference for material selection and high temperature performance research.

Study of Damage Processes in Plasma Sprayed Bond Coat Under Thermal Cycling

1998 ◽  
Author(s):  
P. Bonnet ◽  
S. Abboudl ◽  
B. Normand
Keyword(s):  
High Temperature ◽  
Thermal Cycling ◽  
Bond Coat ◽  
Gas Turbines ◽  
Temperature Oxidation ◽  
Bond Coating ◽  
Engine Efficiency ◽  
Thermal Barriers ◽  
Plasma Sprayed ◽  
Damage Processes

Abstract Plasma sprayed thermal barriers are used as insulating materials in the hot sections of gas turbines to decrease the metal temperatures during service and men allow a higher combustion temperature for better engine efficiency. They usually contain a bond coating to protect the substrate from high temperature oxidation and a top coat with a low thermal conductivity. This study evaluate and identify the mechanisms of degradation of a vacuum plasma sprayed NiCoCrAlYTa bond coat subjected to thermal cycling at high temperature. The microstructure and micro-composition of the coating layer were analyzed by scanning electron microscopy and energy dispersive X-ray analysis to elucidate the improvement and degradation mechanisms of the material. The thermal cycling provokes some morphological and chemical modifications changes within this material. These modifications provoke a perturbation of the heat transfer within the material.

Sintering Behavior of Plasma-Sprayed Sm2Zr2O7 Coating

2010 ◽  
Author(s):  
Jianhua Yu ◽  
Huayu Zhao ◽  
Shunyan Tao ◽  
Xiaming Zhou ◽  
Chuanxian Ding
Keyword(s):  
Thermal Conductivity ◽  
Thermal Expansion ◽  
High Temperature ◽  
Thermal Expansion Coefficient ◽  
Thermal Barrier Coating ◽  
Expansion Coefficient ◽  
Sintering Behavior ◽  
Thermal Barrier ◽  
Barrier Coating ◽  
Plasma Sprayed

Plasma-sprayed thermal barrier coating (TBC) systems are widely used in gas turbine blades to increase turbine entry temperature (TET) and better efficiency. Yttria stabilized zirconia (YSZ) has been the conventional thermal barrier coating material because of its low thermal conductivity, relative high thermal expansion coefficient and good corrosion resistance. However the YSZ coatings can hardly fulfill the harsh requirements in future for higher reliability and the lower thermal conductivity at higher temperatures. Among the interesting TBC candidates, materials with pyrochlore structure show promising thermo-physical properties for use at temperatures exceeding 1200 °C. Sm2Zr2O7 bulk material does not only have high temperature stability, sintering resistance but also lower thermal conductivity and higher thermal expansion coefficient. The sintering characteristics of ceramic thermal barrier coatings under high temperature conditions are complex phenomena. In this paper, samarium zirconate (Sm2Zr2O7, SZ) powder and coatings were prepared by solid state reaction and atmosphere plasma spraying process, respectively. The microstructure development of coatings derived from sintering after heat-treated at 1200–1500 °C for 50 h have been investigated. The microstructure was examined by scanning electron microscopy (SEM) and the grain growth was analyzed in this paper as well.

Modeling Thermal Expansion Behavior of 2.5 D C/SiC Composites in Air Oxidizing Environments between 400 °C and 800 °C

2020 ◽  
Vol 27 (6) ◽  
pp. 861-875
Author(s):  
Xihui Chen ◽  
Zhigang Sun ◽  
Peng Chen ◽  
Yingdong Song ◽  
Xuming Niu
Keyword(s):  
Thermal Expansion ◽  
Thermal Expansion Behavior ◽  
Expansion Behavior ◽  
Sic Composites

EFFECT OF HIGH TEMPERATURE DEFORMATION ON THE LOW THERMAL EXPANSION BEHAVIOR OF FE-29%NI-17%CO ALLOY

2008 ◽  
Vol 22 (31n32) ◽  
pp. 6016-6021 ◽  
Author(s):  
K. A. LEE ◽  
J. NAMKUNG ◽  
M. C. KIM
Keyword(s):  
Thermal Expansion ◽  
High Temperature ◽  
Strain Rate ◽  
Strain Rate Range ◽  
Theoretical Explanation ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Thermal Expansion Behavior ◽  
Low Thermal Expansion ◽  
Expansion Behavior

The effect of high temperature deformation on the low thermal expansion property of Fe -29 Ni -17 Co alloy was investigated in the compressive temperature range of 900~1300°C at a strain rate range of 25 ~ 0.01 sec. -1. The thermal expansion coefficient (α30~400) generally increased with increasing compressive temperature. In particular, α30~400 increased remarkably as the strain rate decreased at temperatures above 1100°C. Note, however, that α30~400 at low compressive temperatures (900°C and 1000°C) increased abnormally at high strain rates. Based on the investigation of various possibilities of change in low thermal expansion behavior, the experimental results indicated that both the appearance of the α phase and evolution of grain size due to hot compression clearly influenced the low thermal expansion behavior of this invar-type alloy. The correlation between the microstructural cause and invar phenomena and theoretical explanation for the low thermal expansion behavior of Fe -29% Ni -17% Co were also suggested.

High temperature structural and thermal expansion behavior of pyrochlore-type praseodymium zirconate

2015 ◽  
Vol 40 (45) ◽  
pp. 15672-15678 ◽  
Author(s):  
R. Shukla ◽  
K. Vasundhara ◽  
P.S.R. Krishna ◽  
A.B. Shinde ◽  
S.K. Sali ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
High Temperature ◽  
Thermal Expansion Behavior ◽  
Expansion Behavior ◽  
Pyrochlore Type

Influences of High Temperature Treatment of C/C on the Mechanical Properties of C/C-SiC Composites

2015 ◽  
Vol 816 ◽  
pp. 78-83
Author(s):  
Dong Lin ◽  
Jing Wang ◽  
Chang Rui Zhang ◽  
Ying Bin Cao ◽  
Rong Jun Liu
Keyword(s):  
Mechanical Properties ◽  
Thermal Expansion ◽  
High Temperature ◽  
Coefficient Of Thermal Expansion ◽  
Temperature Treatment ◽  
High Temperature Treatment ◽  
Sic Composites

C/C-SiC composite as low expansion material for space opto-mechanical structures was prepared by gaseous silicon infiltration after high temperature treatment (HTT) on C/C. 2000°C and 2400°C were selected as the treatment temperatures for C/C to study the influences on the properties of C/C-SiC composite. The graphitization level of amorphous C in C/C was improved by HTT. The porosity of C/C increased from 32.88% to 34.25% (2000°C) and 41.06% (2400°C) respectively. In addition, a higher HTT temperature led to a higher density of C/C-SiC composite and a lower SiC content. Furthermore, the mechanical properties and coefficient of thermal expansion (CTE) of the composite decreased as the temperature increased. After 2000°C HTT, the CTE of C/C-SiC composite decreased to-0.055×10-6·K-1 and the mechanical properties (218 MPa) could meet the application demand at the same time.

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