Development of Operating Temperature Prediction Method Using Thermophysical Properties Change of TBC

2002 ◽  
Author(s):  
Tomoharu Fujii ◽  
Takeshi Takahashi
Keyword(s):  
Thermal Conductivity ◽  
Contact Area ◽  
Operating Temperature ◽  
Thermal Barrier ◽  
Conductivity Measurements ◽  
Temperature Prediction ◽  
Barrier Performance ◽  
Very High ◽  
General Method ◽  
Exposure Conditions

Thermal barrier coatings (TBCs) have become an indispensable technology as the temperature of turbine inlet gas has increased. TBCs reduce the temperature of the base metal, but a reduction of internal pores by sintering occurs when using TBCs, and so the thermal barrier performance of TBCs is deteriorated. This in turn increases the temperature of the base metal and could shorten its lifespan. The authors have already clarified by laboratory acceleration tests that the deterioration of the thermal barrier performance of TBCs is caused by a decrease in the non-contact area that exists inside TBCs [1]. This non-contact area is a slit space that exists between thin layers and is formed when TBCs are coated. This paper examines the relations between the decrease of the non-contact area and the exposure conditions, by measuring the thermal conductivity and the porosity of TBCs exposed to the temperatures that exist in an actual gas turbine, and derives the correlation with exposure conditions. As a result, very high correlations were found between the thermal conductivity and exposure conditions of TBCs, and between the porosity and exposure conditions. A very high correlation was also found between the thermal conductivity and porosity of TBCs. In addition, techniques for predicting TBC operating temperature were examined by using these three correlations. The correlation of diameter and exposure conditions of the gamma prime phase, which exists in nickel base super alloys, is used as a general method for predicting the temperature of parts in hot gas paths [2]. This paper proposes two kinds of operating temperature prediction methods, which are similar to this general method. The first predicts the operating temperature from thermal conductivity measurements of TBCs before and after use, and the second predicts the operating temperature from thermal conductivity measurements of TBCs after use and porosity measurements before use. The TBC operating temperatures of a combustor that had been used for 12,000 hours with an actual E-class gas turbine were predicted by these two methods. The advantage of these methods is that the temperature of all parts with TBC can be predicted.

Development of Operating Temperature Prediction Method Using Thermophysical Properties Change of Thermal Barrier Coatings

2004 ◽  
Vol 126 (1) ◽  
pp. 102-106 ◽  
Author(s):  
T. Fujii ◽  
T. Takahashi
Keyword(s):  
Thermal Conductivity ◽  
Thermal Barrier Coatings ◽  
Operating Temperature ◽  
Thermal Barrier ◽  
Conductivity Measurements ◽  
Barrier Coatings ◽  
Barrier Performance ◽  
Very High ◽  
General Method ◽  
Exposure Conditions

Thermal barrier coatings (TBCs) have become an indispensable technology as the temperature of turbine inlet gas has increased. TBCs reduce the temperature of the base metal, but a reduction of internal pores by sintering occurs when using TBCs, and so the thermal barrier performance of TBCs is deteriorated. This in turn increases the temperature of the base metal and could shorten its lifespan. The authors have already clarified by laboratory acceleration tests that the deterioration of the thermal barrier performance of TBCs is caused by a decrease in the noncontact area that exists inside TBCs. This noncontact area is a slit space that exists between thin layers and is formed when TBCs are coated. This paper examines the relations between the decrease of the noncontact area and the exposure conditions, by measuring the thermal conductivity and the porosity of TBCs exposed to the temperatures that exist in an actual gas turbine, and derives the correlation with exposure conditions. As a result, very high correlations were found between the thermal conductivity and exposure conditions of TBCs, and between the porosity and exposure conditions. A very high correlation was also found between the thermal conductivity and porosity of TBCs. In addition, techniques for predicting TBC operating temperature were examined by using these three correlations. The correlation of diameter and exposure conditions of the gamma prime phase, which exists in nickel base super alloys, is used as a general method for predicting the temperature of parts in hot gas paths. This paper proposes two kinds of operating temperature prediction methods, which are similar to this general method. The first predicts the operating temperature from thermal conductivity measurements of TBCs before and after use, and the second predicts the operating temperature from thermal conductivity measurements of TBCs after use and porosity measurements before use. The TBC operating temperatures of a combustor that had been used for 12,000 hours with an actual E-class gas turbine were predicted by these two methods. The advantage of these methods is that the temperature of all parts with TBC can be predicted.

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.

Development of Actual TBC Exposure Temperature Prediction Method

2004 ◽  
Author(s):  
Masahiko Morinaga ◽  
Tomoharu Fujii ◽  
Takeshi Takahashi
Keyword(s):  
Thermal Conductivity ◽  
Substrate Temperature ◽  
Gas Turbine ◽  
Co2 Laser ◽  
Infrared Camera ◽  
Thermal Barrier ◽  
Remaining Life ◽  
Hot Gas ◽  
Exposure Temperature ◽  
Barrier Performance

Gas turbines are being operated at ever-higher temperatures in order to increase their efficiency. As a result, thermal barrier technology to protect the gas turbine hot gas path parts from high-temperature combustion gas is becoming increasingly important, making it necessary to evaluate the thermal barrier performance of the thermal barrier coating (TBC) coated on these gas turbine hot gas path parts. Thermal barrier performance of the TBC deteriorates with the number of operating hours of the gas turbine. The degradation of TBC thermal barrier performance raises substrate temperature, and this rise in substrate temperature reduces the remaining life of the substrate. We proposed an effective nondestructive inspection (NDI) method to evaluate the thermal barrier performance of the TBC by infrared transient heating of the TBC surface. The temperature behavior closely correlated with the thermal barrier performance of the TBC. The results of numerical analysis and laboratory tests showed that the proposed NDI method was effective for evaluating the thermal barrier performance of TBC. So we developed NDI apparatus to inspect the thermal barrier performance of actual combustion liner TBC. In this NDI apparatus, the surface of the TBC was heated using a CO2 laser, and the temperature of the heated surface measured using an infrared camera. The CO2 laser and infrared camera were fixed, while the measured combustion liner was traversed continuously. The NDI apparatus developed enabled us to inspect the whole inner surface of an actual gas turbine combustion liner. We also showed the correlation with thermal conductivity of a virgin TBC, thermal conductivity of an inspected TBC, operating hours and TBC exposure temperature in our TBC thermophysical property study. The combination of this method and the NDI apparatus developed proved an effective way of clarifying the operating temperature of the hot gas path parts of the gas turbine. In this paper, we show a method for predicting actual gas turbine TBC exposure temperature, important when evaluating the remaining life of gas turbine substrate by the NDI apparatus developed and method of predicting TBC exposure temperature.

Structure and Thermal Conductivity of Nanostructured Hafnia-Based Thermal Barrier Coating Grown on SS-403

2013 ◽  
Vol 4 (1) ◽  
Author(s):  
M. Noor-A-Alam ◽  
A. R. Choudhuri ◽  
C. V. Ramana
Keyword(s):  
Thermal Conductivity ◽  
Room Temperature ◽  
Grazing Incidence ◽  
Thermal Barrier ◽  
Conductivity Measurements ◽  
X Ray Diffraction ◽  
X Ray ◽  
Si Substrates ◽  
Eds Analysis ◽  
Barrier Coating

Yttria-stabilized hafnia (YSH) coatings were grown onto stainless steel 403 (SS-403) and Si substrates. The deposition was made at various growth temperatures ranging from room temperature (RT) to 500 °C. The microstructure and thermal properties of the YSH coatings were evaluated employing grazing incidence X-ray diffraction (GIXRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), and photoacoustic measurements. GIXRD studies indicate that the coatings crystalize in cubic structure with a (111) texturing. Well-grown triangular dense morphology was evident in SEM data. EDS analysis indicates the composition stability of YSH coatings. The grain size increases with the increasing growth temperature. Thermal conductivity measurements indicate lower thermal conductivity of YSH coatings compared to either pure hafnia or yttria-stabilized zirconia.

Estimation of Thermophysical Properties and Microstructure of Aged Thermal Barrier Coatings

2001 ◽  
Author(s):  
Tomoharu Fujii ◽  
Takeshi Takahashi
Keyword(s):  
Thermal Conductivity ◽  
Crystalline Structure ◽  
Plasma Spray ◽  
Thermophysical Properties ◽  
Thermal Barrier ◽  
Powder Size ◽  
Gas Temperature ◽  
Hot Gas ◽  
Heat Treated ◽  
Barrier Performance

A thermal barrier coating (TBC) is used for protecting hot gas path parts, and is useful for allowing the turbine inlet gas temperature to be increased. In order to quantitatively evaluate the performance of TBCs, the thermal conductivity of TBCs on the combustor of a gas turbine were measured. The results indicate that the thermal conductivity of age-deteriorated TBCs were higher than that of the as-sprayed TBC. This finding suggested that the thermal barrier performance of the TBC had deteriorated. When the thermal barrier performance of a TBC deteriorates, the temperature of the metal substrate rises, shortening the service life of hot gas path components. Accordingly, using experimental TBCs, laboratory-scale studies were performed to identify the causes of the deterioration of thermal barrier performance in TBCs. Six types of TBCs, prepared from six grades of plasma spray powder of yttria stabilized zirconia (YSZ), were tested. Average powder size, powder configuration, and percentage of yttria were the parameters of plasma spray powder taken to measure the thermophysical properties and carry out microstructural analyses on the as-sprayed TBCs and heat-treated TBCs. The results of the thermophysical property measurements indicate that the thermal barrier performance of heat-treated TBCs were two to three times greater than that of the as-sprayed TBCs. The results of the microstructural analyses revealed that the deterioration in performance was caused by changes occurring in the crystalline structure and the reduction of the non-contact area as in TBCs. The changes in thermal conductivity of TBCs were expressed as coefficients of porosity, crystalline structure, and heating time and temperature.

WIELAND-K88

Alloy Digest ◽  
2005 ◽  
Vol 54 (12) ◽  
Keyword(s):  
Thermal Conductivity ◽  
Corrosion Resistance ◽  
High Temperature ◽  
Stress Relaxation ◽  
Copper Alloy ◽  
Elevated Temperatures ◽  
Heat Treating ◽  
Relaxation Resistance ◽  
Temperature Performance ◽  
Very High

Abstract Wieland K-88 is a copper alloy with very high electrical and thermal conductivity, good strength, and excellent stress relaxation resistance at elevated temperatures. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on high temperature performance and corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: CU-738. Producer or source: Wieland Metals Inc.

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