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Xueqiang Cao - One of the best experts on this subject based on the ideXlab platform.
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calcium magnesium alumino silicate induced degradation and failure of la 2 zr 0 7 ce 0 3 2 o 7 ysz double Ceramic Layer thermal barrier coatings prepared by electron beam physical vapor deposition
Journal of The European Ceramic Society, 2017Co-Authors: Xin Zhou, Jinshuang Wang, Jieyan Yuan, Junbin Sun, Shujuan Dong, Xueqiang CaoAbstract:Abstract Calcium-magnesium-alumino-silicate (CMAS) induced degradation of the La2(Zr0.7Ce0.3)2O7/YSZ double-Ceramic-Layer thermal barrier coatings (TBCs) prepared by electron beam-physical vapor deposition (EB-PVD) was investigated in this study. CMAS reacted with La2(Zr0.7Ce0.3)2O7 to form a dense crystalline Layer composed of apatite and fluorite phases, while the penetration was not arrested in the double-Ceramic-Layer coating due to the formation of vertical cracks during heat-treatment. In fact, the vertical cracks in the LZ7C3 Layer inevitably provided efficient infiltration paths for molten CMAS to attack the bottom YSZ Layer. Since the formation of Ca2(La1-xCex)8(SiO4)6O26 apatite phase during CMAS reactions led to CaO enrichment in the melt, the YSZ buffer Layer of the double-Ceramic-Layer coating even suffered a severer CMAS attack than the single YSZ coating.
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the application of eu3 photoluminescence piezo spectroscopy in the lamgal11o19 8ysz eu double Ceramic Layer coating system
Journal of The European Ceramic Society, 2015Co-Authors: Sumei Zhao, Zhimin Ren, Yu Zhao, Binglin Zou, Yu Hui, Ling Zhu, Xin Zhou, Xueqiang CaoAbstract:Abstract A non-destructive inspection technique based on the relationship between the stress and peak position of 5D0 → 7F2 transition of Eu3+ ions in 8YSZ has been developed to measure the residual stress in TBCs. A LaMgAl11O19/8YSZ:Eu (LaMA/8YSZ:Eu) double-Ceramic-Layer coating was prepared by atmospheric plasma spraying. Thermal cycling test was conducted and the residual stress in the 8YSZ:Eu Layer was analyzed with the application of the Eu3+ photoluminescence piezo-spectroscopy. There existed both compressive and tensile stresses in the 8YSZ:Eu Layer of the as-sprayed LaMA/8YSZ:Eu coating with an average tensile stress value of 55 MPa. As thermal cycling test going on, the compressive stress disappeared and the tensile stress increased gradually. In addition, the application of 8YSZ:Eu luminescence subLayer could also be used to indicate the spallation and damage degree of LaMA/8YSZ:Eu coating.
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novel thermal barrier coatings based on la2 zr0 7ce0 3 2o7 8ysz double Ceramic Layer systems deposited by electron beam physical vapor deposition
Journal of Alloys and Compounds, 2011Co-Authors: Guanghong Huang, Xueqiang CaoAbstract:Double-Ceramic-Layer (DCL) thermal barrier coatings (TBCs) of La(2)(Zr(0.7)Ce(0.3))(2)O(7) (LZ7C3) and yttria stabilized zirconia (YSZ) were deposited by electron beam-physical vapor deposition (EB-PVD). The thermal cycling test at 1373 K in an air furnace indicates the DCL coating has a much longer lifetime than the single Layer LZ7C3 coating, and even longer than that of the single Layer YSZ coating. The superior sintering-resistance of LZ7C3 coating, the similar thermal expansion behaviors of YSZ interLayer with LZ7C3 coating and thermally grown oxide (TGO) Layer, and the unique growth modes of columns within DCL coating are all very helpful to the prolongation of thermal cycling life of DCL coating. The failure of DCL coating is mainly a result of the reduction-oxidation of cerium oxide, the crack initiation, propagation and extension, the abnormal oxidation of bond coat, the degradation of t'-phase in YSZ coating and the outward diffusion of Cr alloying element into LZ7C3 coating. (C) 2011 Elsevier B.V. All rights reserved.
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double Ceramic Layer thermal barrier coatings based on la2 zr0 7ce0 3 2o7 la2ce2o7 deposited by electron beam physical vapor deposition
Applied Surface Science, 2010Co-Authors: G H Huang, Xueqiang CaoAbstract:Double-Ceramic-Layer (DCL) thermal barrier coatings (TBCs) of La-2(Zr0.7Ce0.3)(2)O-7 (LZ7C3) and La2Ce2O7 (LC) were deposited by electron beam-physical vapor deposition (EB-PVD). The composition, interdiffusion, surface and cross-sectional morphologies, cyclic oxidation behavior of DCL coating were studied. Energy dispersive spectroscopy and X-ray diffraction analyses indicate that both LZ7C3 and LC coatings are effectively fabricated by a single LZ7C3 ingot with properly controlling the deposition energy. The chemical compatibility of LC coating and thermally grown oxide (TGO) Layer is unstable. LaAlO3 is formed due to the chemical reaction between LC and Al2O3 which is the main composition of TGO Layer. Additionally, the thermal cycling behavior of DCL coating is influenced by the interdiffusion of Zr and Ce between LZ7C3 and LC coatings. The failure of DCL coating is a result of the sintering of LZ7C3 coating surface, the chemical incompatibility of LC coating and TGO Layer and the abnormal oxidation of bond coat. Since no single material that has been studied so far satisfies all the requirements for high temperature applications, DCL coating is an important development direction of TBCs. (C) 2010 Elsevier B.V. All rights reserved.
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double Ceramic Layer thermal barrier coatings of la2zr2o7 ysz deposited by electron beam physical vapor deposition
Journal of Alloys and Compounds, 2009Co-Authors: Xinghua Zhong, Yanfei Zhang, Jiangfeng Zhang, Xueqiang CaoAbstract:Double-Ceramic-Layer(DCL) thermal barrier coatings (TBCs) of La2Zr2O7 (LZ) and yttria stabilized zirconia (YSZ) were deposited by electron beam-physical vapor deposition (EB-PVD). The composition, crystal structure, surface and cross-sectional morphologies and cyclic oxidation behavior of the DCL coating were studied. Both the X-ray diffraction (XRD) and thermogravimetric-differential thermal analysis (TG-DTA) prove that LZ and YSZ have good chemical applicability to form a DCL coating. The thermal cycling test at 1373 K in an air furnace indicates the DCL coating has a much longer lifetime than the single Layer LZ coating. and even longer than that of the single Layer YSZ coating. The failure of the DCL coating is a result of both the bond coat oxidation and the thermal strain between bond coat and Ceramic Layer generated by the thermal expansion mismatch.
Liang Wang - One of the best experts on this subject based on the ideXlab platform.
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high temperature oxidation and insulation behavior of plasma sprayed nanostructured thermal barrier coatings
Journal of Alloys and Compounds, 2017Co-Authors: Feifei Zhou, Liang Wang, You Wang, Zhongyuan Cui, Zhenguo ZhangAbstract:Abstract Thermal barrier coatings (TBCs) for more efficient gas turbine engines require higher operating temperature. Adopting pyrochlore structure materials such as rare-earth zirconate and double-Ceramic-Layer (DCL) structure can well satisfy service demands of TBCs at elevated temperature. The nanostructured single-Ceramic-Layer (SCL) 8YSZ, DCL Sm 2 Zr 2 O 7 (SZ)/8YSZ and doping 8 wt% CeO 2 nanoparticles in SZ (8CSZ)/8YSZ TBCs were prepared by atmospheric plasma spraying (APS) in this work. The high temperature oxidation behavior and thermal insulation property of the three kinds of as-sprayed TBCs were investigated systematically at 1000 °C and 1200 °C. The results indicate that the nanostructured DCL 8CSZ/8YSZ TBCs have the best oxidation resistance and thermal insulation property at different temperatures among others. The influence of microstructure on thermal insulation property of the coating has been discussed in detail.
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thermal cycling behavior of nanostructured 8ysz sz 8ysz and 8csz 8ysz thermal barrier coatings fabricated by atmospheric plasma spraying
Ceramics International, 2017Co-Authors: Feifei Zhou, Liang Wang, You Wang, Qiwen Zhang, Chaohui WangAbstract:Abstract The nanostructured single-Ceramic-Layer (SCL) 8YSZ thermal barrier coatings (TBCs), double-Ceramic-Layer (DCL) Sm 2 Zr 2 O 7 (SZ)/8YSZ and SZ doped with 8 wt% CeO 2 nanoscale particles (8CSZ)/8YSZ TBCs were fabricated by atmospheric plasma spraying (APS) on nickel-based superalloy substrates with NiCoCrAlY as the bond coating. The thermal cycling behavior of the three as-sprayed TBCs was investigated systematically at 1000 ℃ and 1200 ℃. The results reveal that the thermal cycling lifetime of the nanostructured DCL 8CSZ/8YSZ TBCs is the longest among them, which is largely due to the fact that the intermediate Layer buffer effect of the DCL structure, more porosity and improvement of thermal expansion coefficient from doping CeO 2 nanoparticles can relieve thermal stress to a great extent at elevated temperature. The failure mechanism of the nanostructured TBCs has been discussed in detail.
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optimized functionally graded la2zr2o7 8ysz thermal barrier coatings fabricated by suspension plasma spraying
Journal of Alloys and Compounds, 2015Co-Authors: Liang Wang, You Wang, Chaohui Wang, Changlong Yang, Xuewei LiAbstract:In this paper, an optimized functionally graded coating (OFGC) was successfully fabricated by suspension plasma spraying (SPS) with feedstocks of the suspension of nanoparticles. La2Zr2O7/8YSZ OFGC with gradual compositional variation along the through-thickness direction is proposed to mitigate spallation and crack formation owing to the high residual stresses caused by frequent thermal cycling for TBCs. The single Ceramic Layer coatings (SCLC) of LZ and double Ceramic Layer coatings (DCLC) of LZ/8YSZ were fabricated by SPS as comparison. The phase composition and microstructure of the SCLC, OFGC and DCLC were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and Energy Dispersive Spectrometer (EDS). Moreover, the thermal cycling tests were carried out to evaluate their thermal shock behavior. Changes in weight and morphology of specimens were analyzed during thermal cycling tests. The results showed that OFGC has extended lifetime compared with SCLC and DCLC. The failure of DCLC with clear interface between different Ceramic Layers occurred via delamination mode, as a result of crack initiation and propagation generated by thermal mismatch between LZ and 8YSZ. While the failure of OFGC occurred in thermally grown oxide (TGO) Layers, indicating that the gradual compositional variation avoided thermal stress concentration in the top Ceramic Layers.
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thermal shock behavior of toughened gadolinium zirconate ysz double Ceramic Layered thermal barrier coating
Journal of Alloys and Compounds, 2014Co-Authors: Xinghua Zhong, Huayu Zhao, Fang Shao, Xiaming Zhou, Shunya Tao, Chenguang Liu, Liang Wang, Kai Yang, Chuanxia DingAbstract:Abstract Double-Ceramic-Layered (DCL) thermal barrier coating system comprising of toughened Gadolinium zirconate (Gd 2 Zr 2 O 7 , GZ) as the top Ceramic Layer and 4.5 mol% Y 2 O 3 partially-stabilized ZrO 2 (4.5YSZ) as the bottom Ceramic Layer was fabricated by plasma spraying and thermal shock behavior of the DCL coating was investigated. The GZ top Ceramic Layer was toughened by addition of nanostructured 3 mol% Y 2 O 3 partially-stabilized ZrO 2 (3YSZ) to improve fracture toughness of the matrix. The thermal shock resistance of the DCL coating was enhanced significantly compared to that of single-Ceramic-Layered (SCL) GZ-3YSZ composite coating, which is believed to be primarily attributed to the two factors: (i) the increase in fracture toughness of the top Ceramic Layer by incorporating nanostructured YSZ particles and (ii) the improvement in strain tolerance through the utilization of 4.5YSZ as the bottom Ceramic Layer. In addition, the failure mechanisms are mainly attributed to the still low fracture toughness of the top Ceramic Layer and oxidation of the bond-coat.
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finite element simulation of stress distribution and development in 8ysz and double Ceramic Layer la2zr2o7 8ysz thermal barrier coatings during thermal shock
Applied Surface Science, 2012Co-Authors: C H Wang, Y. Wang, Liang Wang, Wei ZhangAbstract:Abstract In this paper, the thermal stress of the double-Ceramic-Layer (DCL) La2Zr2O7/8YSZ thermal barrier coatings (TBCs) fabricated by atmospheric plasma spraying (APS) during thermal shock has been calculated. The residual stress of the coating after being sprayed has been regarded as the initial condition of the first thermal cycle. The characteristic of the stress development during the thermal cycle has been discussed, and the influence of the defects on the failure mode during the thermal cycle has also been discussed systematically. Finite element simulation results show that there exist higher radial thermal shock stresses on the Ceramic Layer surface of these two coatings. There also exist higher thermal stress gradient at the interface between the Ceramic Layer and the metallic Layer. Higher thermal stress in 8YSZ/NiCoCrAlY coating lead to the decrease of thermal shock property as compared to that of LZ/8YSZ/NiCoCrAlY coating. The addition of LZ Ceramic Layer can increase the insulation temperature, impede the oxygen transferring to the bond coating and can also reduce the thermal stress. Considering from the aspects of thermal insulation ability and the thermal shock resistance ability, DCL type LZ/8YSZ TBCs is a more promising coating material compared with the single-Ceramic-Layer (SCL) type 8YSZ TBCs for the application.
C H Wang - One of the best experts on this subject based on the ideXlab platform.
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thermal shock behavior of 8ysz and double Ceramic Layer la2zr2o7 8ysz thermal barrier coatings fabricated by atmospheric plasma spraying
Ceramics International, 2012Co-Authors: Lujie Wang, J Q He, C H Wang, Y. WangAbstract:Abstract The single-Ceramic-Layer (SCL) 8YSZ (conventional and nanostructured 8YSZ) and double-Ceramic-Layer (DCL) La 2 Zr 2 O 7 (LZ)/8YSZ thermal barrier coatings (TBCs) were fabricated by plasma spraying on nickel-based superalloy substrates with NiCrAlY as the bond coat. The thermal shock behavior of the three as-sprayed TBCs at 1000 °C and 1200 °C was investigated. The results indicate that the thermal cycling lifetime of LZ/8YSZ TBCs is longer than that of SCL 8YSZ TBCs due to the fact that the DCL LZ/8YSZ TBCs further enhance the thermal insulation effect, improve the sintering resistance ability and relieve the thermal mismatch between the Ceramic Layer and the metallic Layer at high temperature. The nanostructured 8YSZ has higher thermal shock resistance ability than that of the conventional 8YSZ TBC which is attributed to the lower tensile stress in plane and higher fracture toughness of the nanostructured 8YSZ Layer. The pre-existed cracks in the surface propagate toward the interface vertically under the thermal activation. The nucleation and growth of the horizontal crack along the interface eventually lead to the failure of the coating. The crack propagation modes have been established, and the failure patterns of the three as-sprayed coatings during thermal shock have been discussed in detail.
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finite element simulation of stress distribution and development in 8ysz and double Ceramic Layer la2zr2o7 8ysz thermal barrier coatings during thermal shock
Applied Surface Science, 2012Co-Authors: C H Wang, Y. Wang, Liang Wang, Wei ZhangAbstract:Abstract In this paper, the thermal stress of the double-Ceramic-Layer (DCL) La2Zr2O7/8YSZ thermal barrier coatings (TBCs) fabricated by atmospheric plasma spraying (APS) during thermal shock has been calculated. The residual stress of the coating after being sprayed has been regarded as the initial condition of the first thermal cycle. The characteristic of the stress development during the thermal cycle has been discussed, and the influence of the defects on the failure mode during the thermal cycle has also been discussed systematically. Finite element simulation results show that there exist higher radial thermal shock stresses on the Ceramic Layer surface of these two coatings. There also exist higher thermal stress gradient at the interface between the Ceramic Layer and the metallic Layer. Higher thermal stress in 8YSZ/NiCoCrAlY coating lead to the decrease of thermal shock property as compared to that of LZ/8YSZ/NiCoCrAlY coating. The addition of LZ Ceramic Layer can increase the insulation temperature, impede the oxygen transferring to the bond coating and can also reduce the thermal stress. Considering from the aspects of thermal insulation ability and the thermal shock resistance ability, DCL type LZ/8YSZ TBCs is a more promising coating material compared with the single-Ceramic-Layer (SCL) type 8YSZ TBCs for the application.
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finite element simulation of residual stress of double Ceramic Layer la2zr2o7 8ysz thermal barrier coatings using birth and death element technique
Computational Materials Science, 2012Co-Authors: Liang Wang, Y. Wang, Xinyang Sun, Z Y Pan, C H WangAbstract:Abstract In this paper, the residual stress of double-Ceramic-Layer (DCL) La2Zr2O7/8YSZ thermal barrier coatings (TBCs) fabricated by atmospheric plasma spraying (APS) was calculated by finite element simulation using birth and death element technique. The residual stress was composed of two parts, i.e. the quenching stress and the thermal stress. The simulation results indicated that the surface and the edge of interface are often the positions of stress concentration. The DCL La2Zr2O7/8YSZ has lower residual stress compared with that of the single-Ceramic-Layer (SCL) 8YSZ TBCs with the same thickness. In addition, the influence of defects on the residual stress has been calculated and discussed using finite element method combined with Computational Micro-Mechanics (CMM). As the DCL TBCs has better thermal insulation effect, sintering resistance ability and lower residual stress compared with that of the SCL 8YSZ at the same time, it was expected to be an ideal candidate material for the application in the future.
Xinghua Zhong - One of the best experts on this subject based on the ideXlab platform.
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thermal shock behavior of toughened gadolinium zirconate ysz double Ceramic Layered thermal barrier coating
Journal of Alloys and Compounds, 2014Co-Authors: Xinghua Zhong, Huayu Zhao, Fang Shao, Xiaming Zhou, Shunya Tao, Chenguang Liu, Liang Wang, Kai Yang, Chuanxia DingAbstract:Abstract Double-Ceramic-Layered (DCL) thermal barrier coating system comprising of toughened Gadolinium zirconate (Gd 2 Zr 2 O 7 , GZ) as the top Ceramic Layer and 4.5 mol% Y 2 O 3 partially-stabilized ZrO 2 (4.5YSZ) as the bottom Ceramic Layer was fabricated by plasma spraying and thermal shock behavior of the DCL coating was investigated. The GZ top Ceramic Layer was toughened by addition of nanostructured 3 mol% Y 2 O 3 partially-stabilized ZrO 2 (3YSZ) to improve fracture toughness of the matrix. The thermal shock resistance of the DCL coating was enhanced significantly compared to that of single-Ceramic-Layered (SCL) GZ-3YSZ composite coating, which is believed to be primarily attributed to the two factors: (i) the increase in fracture toughness of the top Ceramic Layer by incorporating nanostructured YSZ particles and (ii) the improvement in strain tolerance through the utilization of 4.5YSZ as the bottom Ceramic Layer. In addition, the failure mechanisms are mainly attributed to the still low fracture toughness of the top Ceramic Layer and oxidation of the bond-coat.
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double Ceramic Layer thermal barrier coatings of la2zr2o7 ysz deposited by electron beam physical vapor deposition
Journal of Alloys and Compounds, 2009Co-Authors: Xinghua Zhong, Yanfei Zhang, Jiangfeng Zhang, Xueqiang CaoAbstract:Double-Ceramic-Layer(DCL) thermal barrier coatings (TBCs) of La2Zr2O7 (LZ) and yttria stabilized zirconia (YSZ) were deposited by electron beam-physical vapor deposition (EB-PVD). The composition, crystal structure, surface and cross-sectional morphologies and cyclic oxidation behavior of the DCL coating were studied. Both the X-ray diffraction (XRD) and thermogravimetric-differential thermal analysis (TG-DTA) prove that LZ and YSZ have good chemical applicability to form a DCL coating. The thermal cycling test at 1373 K in an air furnace indicates the DCL coating has a much longer lifetime than the single Layer LZ coating. and even longer than that of the single Layer YSZ coating. The failure of the DCL coating is a result of both the bond coat oxidation and the thermal strain between bond coat and Ceramic Layer generated by the thermal expansion mismatch.
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thermal stability of double Ceramic Layer thermal barrier coatings with various coating thickness
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2006Co-Authors: Xinghua Zhong, Yanfei Zhang, Jiayan Li, Jian MengAbstract:Double-Ceramic-Layer (DCL) coatings with various thickness ratios composed of YSZ (6-8 wt.% Y2O3 + ZrO2) and lanthanum zirconate (LZ, La2Zr2O7) were produced by the atmospheric plasma spraying. Chemical stability of LZ in contact with YSZ in DCL coatings was investigated by calcining powder blends at different temperatures. No obvious reaction was observed when the calcination temperature was lower than 1250 degrees C, implying that LZ and YSZ had good chemical applicability for producing DCL coating. The thermal cycling test indicate that the cycling lives of the DCL coatings are strongly dependent on the thickness ratio of LZ and YSZ, and the coatings with YSZ thickness between 150 and 200 mu m have even longer lives than the single-Layer YSZ coating. When the YSZ Layer is thinner than 100 mu m, the DCL coatings failed in the LZ Layer close to the interface of YSZ Layer and LZ Layer. For the coatings with the YSZ thickness above 150 mu m, the failure mainly occurs at the interface of the YSZ Layer and the bond coat.
Chaohui Wang - One of the best experts on this subject based on the ideXlab platform.
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thermal cycling behavior of nanostructured 8ysz sz 8ysz and 8csz 8ysz thermal barrier coatings fabricated by atmospheric plasma spraying
Ceramics International, 2017Co-Authors: Feifei Zhou, Liang Wang, You Wang, Qiwen Zhang, Chaohui WangAbstract:Abstract The nanostructured single-Ceramic-Layer (SCL) 8YSZ thermal barrier coatings (TBCs), double-Ceramic-Layer (DCL) Sm 2 Zr 2 O 7 (SZ)/8YSZ and SZ doped with 8 wt% CeO 2 nanoscale particles (8CSZ)/8YSZ TBCs were fabricated by atmospheric plasma spraying (APS) on nickel-based superalloy substrates with NiCoCrAlY as the bond coating. The thermal cycling behavior of the three as-sprayed TBCs was investigated systematically at 1000 ℃ and 1200 ℃. The results reveal that the thermal cycling lifetime of the nanostructured DCL 8CSZ/8YSZ TBCs is the longest among them, which is largely due to the fact that the intermediate Layer buffer effect of the DCL structure, more porosity and improvement of thermal expansion coefficient from doping CeO 2 nanoparticles can relieve thermal stress to a great extent at elevated temperature. The failure mechanism of the nanostructured TBCs has been discussed in detail.
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optimized functionally graded la2zr2o7 8ysz thermal barrier coatings fabricated by suspension plasma spraying
Journal of Alloys and Compounds, 2015Co-Authors: Liang Wang, You Wang, Chaohui Wang, Changlong Yang, Xuewei LiAbstract:In this paper, an optimized functionally graded coating (OFGC) was successfully fabricated by suspension plasma spraying (SPS) with feedstocks of the suspension of nanoparticles. La2Zr2O7/8YSZ OFGC with gradual compositional variation along the through-thickness direction is proposed to mitigate spallation and crack formation owing to the high residual stresses caused by frequent thermal cycling for TBCs. The single Ceramic Layer coatings (SCLC) of LZ and double Ceramic Layer coatings (DCLC) of LZ/8YSZ were fabricated by SPS as comparison. The phase composition and microstructure of the SCLC, OFGC and DCLC were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and Energy Dispersive Spectrometer (EDS). Moreover, the thermal cycling tests were carried out to evaluate their thermal shock behavior. Changes in weight and morphology of specimens were analyzed during thermal cycling tests. The results showed that OFGC has extended lifetime compared with SCLC and DCLC. The failure of DCLC with clear interface between different Ceramic Layers occurred via delamination mode, as a result of crack initiation and propagation generated by thermal mismatch between LZ and 8YSZ. While the failure of OFGC occurred in thermally grown oxide (TGO) Layers, indicating that the gradual compositional variation avoided thermal stress concentration in the top Ceramic Layers.