scholarly journals Effect of La2O3 on Microstructure and Thermal Conductivity of La2O3-Doped YSZ Coatings

Materials ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 2966 ◽  
Author(s):  
Xiaojie Guo ◽  
Chucheng Lin ◽  
Jimei Zhang ◽  
Ziwei Liu ◽  
Caifen Jiang ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Barrier Coatings ◽  
Lattice Parameter ◽  
Atmospheric Plasma Spraying ◽  
Yttria Stabilized Zirconia ◽  
Atmospheric Plasma ◽  
Thermal Barrier ◽  
Stabilized Zirconia ◽  
Barrier Coatings ◽  
Co Doped

Enhancing the properties of thermal barrier coatings (TBCs) by doping with rare earth elements has been a hot topic for a while. La2O3 and Y2O3 co-doped ZrO2 (La-YSZ) TBCs and yttria-stabilized zirconia (YSZ) TBCs were deposited by atmospheric plasma spraying (APS), and the comprehensive effects of La3+ on the microstructure and property were investigated. The thermal conductivity and microstructure were investigated and were compared with YSZ. The recrystallized fraction components of all TBCs were quantified. It is clearly found that the component of “recrystallized” and “deformed” grains for La-YSZ TBCs is much higher than that for YSZ TBCs. This could be due to La3+ doping enlarging the lattice parameter of YSZ and thus increasing the melting index, which in turns leads to the smaller grain size of La-YSZ TBCs. As a result, the thermal conductivities of La-YSZ TBCs were distinctly lower than those of YSZ TBCs.

scholarly journals Effect of Different Types of Pores on Thermal Conductivity of YSZ Thermal Barrier Coatings

Coatings ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 138 ◽  
Author(s):  
Yiling Huang ◽  
Ningning Hu ◽  
Yi Zeng ◽  
Xuemei Song ◽  
Chucheng Lin ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Barrier Coatings ◽  
Cross Section ◽  
Quantitative Relationship ◽  
Yttria Stabilized Zirconia ◽  
Atmospheric Plasma ◽  
Thermal Barrier ◽  
Stabilized Zirconia ◽  
Barrier Coatings ◽  
Different Types

Atmospheric plasma spray (APS) yttria-stabilized zirconia coatings have a complex microstructure with a variety of pores that significantly reduce the thermal conductivity. APS thermal barrier coatings (TBCs) with a similar monoclinic phase were prepared. The pore sizes and distributions of the coatings were obtained by scanning their cross-section via SEM; the scanned areas were over 1 mm × 2 mm and more than 23,000 pores for each coating were analyzed. Multiple linear regression was used to analyze the porosity data and then to determine the quantitative relationship between different types of pores and thermal conductivity. Results revealed that the different pores have different effects on decreasing the thermal conductivity. The small, vertical pores have the biggest effect, while the horizontal pores also play a significant role in decreasing the thermal conductivity.

Thermophysical Properties of Samarium-Cerium Oxide for Thermal Barrier Coatings Application

2007 ◽  
Vol 336-338 ◽  
pp. 1773-1775 ◽  
Author(s):  
Chun Lei Wan ◽  
Wei Pan ◽  
Zhi Xue Qu ◽  
Ye Xia Qin
Keyword(s):  
Thermal Conductivity ◽  
Thermal Expansion ◽  
Thermal Barrier Coatings ◽  
Thermophysical Properties ◽  
Ceramic Coating ◽  
Fluorite Structure ◽  
Yttria Stabilized Zirconia ◽  
Thermal Barrier ◽  
Stabilized Zirconia ◽  
Barrier Coatings

Sm0.4Ce0.6O1.8 specimen with a defective fluorite structure was synthesized and its thermophysical properties were characterized for thermal barrier coatings (TBCs) application. At high temperature, Sm0.4Ce0.6O1.8 exhibited much lower thermal conductivity than 7wt% yttria-stabilized zirconia (7YSZ)-the commonly used composition in current TBCs. Sm0.4Ce0.6O1.8 also possessed large thermal expansion coefficient, which could help reduce the thermal mismatch between the ceramic coating and bond coat.

scholarly journals A Comparative Study on the Synthesis and Properties of Yttria Stabilized Zirconia (YSZ) and Lanthana Doped YSZ Plasma Sprayed Thermal Barrier Coatings

2013 ◽  
Author(s):  
S. T. Aruna ◽  
N. Balaji ◽  
B. Arul Paligan
Keyword(s):  
Thermal Conductivity ◽  
Thermal Barrier Coatings ◽  
Gas Turbines ◽  
Operating Temperature ◽  
Yttria Stabilized Zirconia ◽  
Thermal Barrier ◽  
Spray Parameters ◽  
Stabilized Zirconia ◽  
Barrier Coatings ◽  
Plasma Sprayed

Ceramic thermal barrier coatings (TBCs) have been used for decades to extend the life of combustors and high temperature turbine stationary and rotating components to increase the operating temperature and in turn the performance of gas turbines or diesel engines can be increased. At present, thermal barrier coatings (TBCs) of Y2O3 partially stabilized ZrO2 (YSZ) films are widely used. In recent years ceramic compositions useful in thermal barrier coatings having reduced thermal conductivity are being explored to further increasing the operating temperature of gas turbines and improve the engine efficiency. In the present study, a comparison of the properties of state-of-the art 8wt% yttria stabilized zirconia (YSZ) and lanthana doped YSZ plasma sprayed coatings is presented. Plasma sprayable powders were prepared in the laboratory by a single step precipitation method and characterized. Both the powders had good flowability. These powders were plasma sprayed at identical critical plasma spray parameters. The coatings were characterized for phase, microstructure and thermal conductivity. Both the powders and coatings exhibited tetragonal form of zirconia and no traces of lanthana were observed. Both the coatings exhibited similar porosity levels. Microstructure of the coatings revealed porous coating with good adhesion of the bondcoat with the topcoat. Plasma sprayed 8wt% YSZ and lanthana doped YSZ exhibited thermal conductivity values of 0.88 and 0.67 W m−1 K−1 respectively which is lower than that reported in literature. This study shows that lanthana doping in YSZ helps in lowering the thermal conductivity and hence this coating may be a potential candidate for TBC application.

Failure Mechanism of Yttria Stabilized Zirconia Atmospheric Plasma Sprayed Thermal Barrier Coatings Subjected to Calcia-Magnesia-Alumino-Silicate Environmental Attack

2017 ◽  
Vol 270 ◽  
pp. 39-44 ◽  
Author(s):  
Ladislav Čelko ◽  
David Jech ◽  
Pavel Komarov ◽  
Michaela Remešová ◽  
Karel Dvořák ◽  
...  
Keyword(s):  
Thin Layer ◽  
Thermal Barrier Coatings ◽  
Yttria Stabilized Zirconia ◽  
Atmospheric Plasma ◽  
Thermal Barrier ◽  
Stabilized Zirconia ◽  
Barrier Coatings ◽  
Alumino Silicate ◽  
Plasma Sprayed ◽  
Environmental Attack

The contribution focuses on the description of failure mechanism of atmospheric plasma sprayed multilayer thermal barrier coatings subjected to calcia-magnesia-alumino-silicate (CMAS) environmental attack. To identify exothermic and endothermic reactions which occurred during heating/cooling by means of calorimetry was also utilized initial yttria stabilized zirconia (YSZ) powder subsequently used for thermal spraying of multilayer thermal barrier coating system (TBCs), CMAS powder later on utilized for thin layer deposition and its mixture. Atmospheric plasma spray technique was used to produce the TBCs on a grit blasted nickel-based superalloy substrates, where CoNiCrAlY powder was used for deposition of a bond coat and YSZ powder was sprayed as a top coat. In accordance to the aerospace standard the thin layer of CMAS was deposited on as sprayed TBCs samples surface from its colloidal solution by paint brush method. Burner-rig test, utilizing direct propane-oxygen flame, was used for thermal cyclic exposition of the multilayer coated samples at the temperature of 1150 °C. Samples after thermal cyclic exposure test were investigated by means of materialographic analysis approaches. The significant reduction in life-time of CMAS coated YSZ top coat was observed due to lower melting point phase formation and molten silicate crystallization within the pores providing the spallation identified as a major mechanism of TBCs failure.

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