Thick Thermal Barrier Coatings Research Articles

Thermal barrier coating for carbon fiber-reinforced composite materials

Carbon fiber-reinforced plastic (CFRP) composites are widely employed in lightweight and high performance applications including supercars, aero-vehicles, and space components. However, although carbon fibers are thermally stable, the low thermal endurance of the matrix materials remains a critical problem in terms of the performance of the material. In this study, we proposed a new, Al 2 O 3 -based thermal barrier coating (TBC) for the CFRP composites. The TBC comprised α-phase Al 2 O 3 particles with a mean diameter of 9.27 μm. The strong adhesion between the TBC and the CFRP substrate was evaluated using a three-point bending test. When the CFRP substrate was subjected to a 500–700 °C flame, the 1.45-mm thick TBC protected the CFRP substrate remarkably by reducing the surface temperature to 188–228 °C. The thermo-mechanical responses of this TBC/CFRP composite were analyzed after thermal shock tests. Surprisingly, 50% of the pristine flexural strength of the TBC/CFRP composite was preserved, whereas that of neat CFRP was reduced significantly by 95%.

Atmospheric plasma sprayed thick thermal barrier coatings: Microstructure, thermal shock behaviors and failure mechanism

Advanced thick thermal barrier coatings (TTBCs) have attracted extensive attentions due to the embedded segmentation-crack structure and excellent thermal insulation performance. The thermal shock life and failure behaviors of advanced TTBCs still remain a challenge. The objective of this work is to well understand the effect of microstructure on the coating cracking behavior in atmospheric plasma sprayed TTBCs system, in which the extended Raman spectroscopy (RS) techniques are used to obtain an in-depth understanding on how the oxidation affects the stress distribution in coatings and in turn, the causes of the observed cracking. Results show that the TTBCs deposited by the highly purified feedstock exhibit excellent thermal shock life at 1100 ℃ due to the well-proportioned and compact structure and built-in vertical cracks. After thermal shock test, the broken regions usually occur at the horizontal cracks and vertical cracks area within top-coat, and top-coat/bondcoat interface, which may suggest that each structural mutation parts are prone to causing the TTBCs instabilities. Cracks are propagated and extended under thermal tensile stress. The coating failure is most possibly dominated by the accumulated residual stress generated due to thermal expansion mismatch between the substrate and top-coat. In addition, the good thermal shock resistance have a close relationship with the newly formed vertical cracks at the bottom of ceramic coating near the top-coat/bondcoat interface.

Thermal Analysis and Creep Lifetime Prediction Based on the Effectiveness of Thermal Barrier Coating on a Gas Turbine Combustor Liner Using Coupled CFD and FEM Simulation

Thermal barrier coating (TBC) plays a vital role in the gas turbine combustor liner (CL) to mitigate the internal heat transfer from combustion gas to the CL and enhance the parent material lifetime of the CL. This present study examined the thermal analysis and creep lifetime prediction based on three different TBC thicknesses, 400, 800, and 1200 μm, coated on the inner CL using the coupled computational fluid dynamics/finite element method. The simulation method was divided into three models to minimize the amount of computational work involved. The Eddy Dissipation Model was used in the first model to simulate premixed methane-air combustion, and the wall temperature of the inner CL was obtained. The conjugate heat transfer simulation on the external cooling flows from the rib turbulator, impingement jet, and cross flow, and the wall temperature of the outer CL was obtained in the second model. The thermal analysis was carried out in the third model using three different TBC thicknesses and incorporating the wall data from the first and second model. The effect of increasing TBC thickness shows that the TBC surface temperature was increased. Thereby, the inner CL metal temperature was decreased due to the TBC thickness as well as the material properties of Yttria Stabilized Zirconia, which has low thermal conductivity and a high thermal expansion coefficient. With the increase in TBC thickness, the average temperature difference between the TBC surface and the inner metal surface increased. In contrast, the average temperature difference between the inner and outer metal surfaces remained nearly constant. The von Mises equivalent stress, based on the material property and thermal expansion coefficient, was determined and used to find the creep lifetime of the CL using the Larson–Miller rupture curve for all TBC thickness cases in order to analyze the thermo-structure. Except in the C-channel, the increasing TBC thickness was found to effectively increase the CL lifespan. Furthermore, the case without TBC was compared with the damaged CL with cracks due to thermal stress, which was prevented by increasing TBC thickness shown in this present study.

Thermal-Fluid-Solid Coupling Analysis on the Temperature and Thermal Stress Field of a Nickel-Base Superalloy Turbine Blade.

Based on the establishment of the original and improved models of the turbine blade, a thermal-fluid-solid coupling method and a finite element method were employed to analyze the internal and external flow, temperature, and thermal stress of the turbine blade. The uneven temperature field, the thermal stress distribution characteristics of the composite cooling turbine blade under the service conditions, and the effect of the thickness of the thermal barrier coating (TBC) on the temperature and thermal stress distributions were obtained. The results show that the method proposed in this paper can better predict the ablation and thermal stress damage of turbine blades. The thermal stress of the blade is closely related to the temperature gradient and local geometric structure of the blade. The inlet area of the pressure side-platform of the blade, the large curvature region of the pressure tip of the blade, and the rounding between the blade body and the platform on the back of the blade are easily damaged by thermal stress. Cooling structure optimization and thicker TBC thickness can effectively reduce the high temperature and temperature gradient on the surface and inside of the turbine blade, thereby reducing the local high thermal stress.

Tribological and thermal characterization of electron beam physical vapor deposited single layer thin film for TBC application

Thin-film coatings have been commonly used in the automotive industry for a variety of applications. Thermal barrier coatings (TBCs) are designed to extend the life of combustors and turbine blades while mitigating high-temperature issues. In this study, an attempt has been made to develop a single-layer thin film as TBCs for engine applications. Yttria Stabilized Zirconia(YSZ) and Lanthanum Zirconate(LZ) were selected as the coating materials. The physical and chemical characteristics of target materials were studied using Scanning Electron Microscope (SEM), Energy Dispersive x-ray Spectroscopy (EDS), and x-ray Diffraction Analysis (XRD). FCD 400 has been taken as the substrates for this study. In general, TBCs thicknesses are usually about 100–300 μm, while in this work, a coating thickness of 750 nm is attempted using EB-PVD and its performance was evaluated. The mechanical, tribological, and thermal behaviors of the uncoated and coated substrates were characterized as per ASTM standards. Maximum hardness of 3.68 GPa was observed on the YSZ coated substrates. The average Coefficient of Friction (COF) and Coefficient of Thermal Expansion(CTE) values of YSZ coated substrates were 0.334 and 1.33 × 10–5 K−1, respectively, which were comparatively lower than LZ and uncoated substrates. On the contrary, the adhesive characteristics of YSZ and LZ coated substrates were enhanced, which was evident from their results of 6.28N and 6.19N respectively. The thermal conductivity of LZ coated substrates was found to be 3.2% lower than YSZ and 11% lower than uncoated substrates, respectively. From the results, it is observed that LZ thin film coating have better thermal properties than YSZ, which is best suited for TBCs application. Following evaluation of thin-film coatings, confirms that thin-film TBCs are a reliable approach for thermal and wear production as compared to thick TBCs, and their extended life could improve productivity and economic benefits for automotive industries.

A comprehensive experimental investigation of low-temperature combustion with thick thermal barrier coatings

Thick thermal barrier coatings (TBCs) have a significant potential to increase thermal efficiency by reducing heat transfer losses. However, in conventional combustion modes, the drawbacks associated with charge heating and higher propensity to knock have outweighed the efficiency benefits. Since the advanced low-temperature combustion (LTC) concepts are fundamentally different from the conventional combustion modes, these penalties do not exist in most of LTCs.The current experimental study shows the feasibility and benefits of thick TBCs with advanced LTC enabled by two different fuels: conventional gasoline and wet ethanol 80 (WE80, i.e., 80% ethanol and 20% water by mass). A total of five pistons were tested, including two metal baselines and three TBC-coated pistons with different thicknesses or surface finishes. A load sweep was conducted with each fuel on each piston within the same constraints. The thick TBCs extends the low load limit by about 15% for both gasoline and WE80 cases. A deterioration of the high load limit was not observed, which implies that the charge heating penalty does not occur in LTCs. The combustion efficiency increased for the thicker TBC by up to 2% points, and the fuel conversion efficiency was increased by up to 4.3%. The gasoline cases experience the largest benefits at low load, while the wet ethanol experiences the largest benefits at mid-to-high load. The intake temperature requirement is successfully reduced by 10–15 K. It is also observed that the dense sealing layer results in a significant improvement to UHC emissions. All of the coated pistons survived the 10–20 h of engine operation with no visual failure.

Interplay of the phase and the chemical composition of the powder feedstock on the properties of porous 8YSZ thermal barrier coatings

Some chemical impurities enhance sintering kinetics of ceramic Thermal Barrier Coatings (TBCs) which can cause their premature failure during operation in gas turbine engine by causing reduction in coating’s strain compliance as well as faster bond-coat oxidation due to increased thermal conductivity. Certain chemical impurities are also believed to suppress resistance to tetragonal to monoclinic phase transformation in 8YSZ, which can also be an important factor regarding TBC’s performance. Most of the impurities and some of the monoclinic phase present in the powder feedstocks can survive into the as-sprayed coating. Therefore, there is a general trend towards OEMs requiring the lowest amounts of chemical impurities and the lowest amounts of monoclinic phase in the powder feedstocks. This paper presents a comprehensive investigation aimed at understanding the role and the relative importance of the chemical and phase purities of the powder feedstock for the properties and performance of thick 8YSZ TBCs.

Thermal Stability of YSZ Thick Thermal Barrier Coatings Deposited by Suspension and Atmospheric Plasma Spraying

Two types of segmentation-crack structured yttria-stabilized zirconia (YSZ) thick thermal barrier coatings (>500 μm, TTBCs) were deposited onto the stainless steel substrates using atmospheric plasma spraying (APS) and suspension plasma spraying (SPS) process, respectively. In this work, thermal aging behaviors, such as the microstructures, phase compositions, grain growth, and mechanical properties of APS TTBCs and SPS TTBCs, were systematically investigated. Results showed that both as-sprayed TTBCs exhibited a typical segmentation-crack structure in the through-thickness direction. APS coatings mainly comprised of larger columnar crystals, while a large number of smaller equiaxed grains existed in SPS coatings. Both of the coatings underwent tetragonal-monoclinic phase transformation after 155 °C/40 h heat treatment. The poorer phase stability of SPS TTBCs may have a connection with smaller grain size. Thermal-aged APS and SPS coatings exhibited a significant increase in H and E values with the rising of thermal aging temperature, and for the samples that thermal aged at 1550 °C, the H and E values increased sharply during initial stage then decreased after 80 h due to the phase decomposition. The segmented APS coatings had weak bonding between the lamellaes during thermal exposure, which caused the mean Vickers hardness value of APS TTBCs to be much lower than that of SPS TTBCs.

Thermal Stability of Plasma-Sprayed Thick Thermal Barrier Coatings Using Triplex ProTM-200 Torch

Segmentation-crack structured yttria-stabilized zirconia (YSZ) thermal barrier coatings (TBCs) were deposited by atmospheric plasma spraying (APS) using a Triplex Pro™-200 gun. In this work, free-standing coating specimens (~700 μm) were isothermally heat-treated in air from 1200 to 1600 °C for 24 h and at 1550 °C for 20 to 100 h, respectively. The thermal aging behaviors such as microstructures, phase compositions, grain growth and mechanical properties were characterized via scanning electron microscopy (SEM), X-ray diffraction (XRD), electron backscatter diffraction (EBSD) and a Vickers hardness test. The results indicated that the as-sprayed coatings mainly consisted of metastable tetragonal (t′-YSZ) phase, but the t′-YSZ gradually partitioned into equilibrium tetragonal (t-YSZ) and cubic (c-YSZ) phases due to yttrium diffusion during thermal exposure, and with an improvement in temperature, the c-YSZ may retain or transform into another yttrium-rich tetragonal (t″-YSZ) phase. The transformation of t-YSZ to monoclinic phase (m-YSZ) has occurred after 1550 °C/40 h heat treatment, and the content of the m-YSZ phase increased with the prolongation of the thermal exposure time. The variations of Vickers hardness have a correlation with pores healing and grain growth, which might be attributed to the coating sintering and m-YSZ phase formation. Furthermore, the growth pattern of the grains was investigated in detail. In service, cracks and pores proceeded along the grain boundaries, especially surrounding the small grains. It is conducive to the engineering application of TBCs fabricated with the Triplex Pro™-200 gun.

Sensitivity analysis of internal layout and coating thickness to overall cooling performances of laminated cooling configurations with surface thermal barrier coatings

Laminated cooling coupled by surface thermal barrier coating (TBC) has a large potential to provide the effective protection to components in next-generation gas turbines. However, the conjugate heat transfer characteristics of coupling system is reported rarely. In this work, the combined effects of internal element layout, coating thickness and cooling air amount on the metal and TBC surface temperatures were discussed. The conjugate heat transfer experiments were conducted under engine-similar hot-side Biot (Bi) numbers and mainstream-to-coolant temperature ratio, and thus, a low conductivity material was applied to simulate the actual TBC. Four TBC thicknesses could cause BiTBC/BiMetal = 1.5, 3.0, 4.5 and 6.0 in the actual operating range. The results revealed the TBCs with BiTBC/BiMetal ≥ 4.5 can generate a large thermal resistance to reduce the metal temperature and hence a 50% increment in metal overall cooling effectiveness. However, the dominated internal cooling was also isolated to cause an increase of exterior surface temperature of entire cooling scheme, and a significant reduction of cooling air effect. The surface temperature variations were affected by the internal layout, when adopting the TBCs with BiTBC/BiMetal ≤ 3.0. Relative to the coolant amount and TBC thickness, the sensitivities of cooling effectiveness with internal layout were non-significant.

Formation of vertical cracks in air plasma sprayed YSZ coatings using unpyrolyzed powder

Thick thermal barrier coatings (TTBCs) with vertical cracks deposited by air plasma spray (APS) and solution precursor plasma spray (SPPS) techniques have been widely investigated to achieve good thermal insulation along with reasonable service life. In this study, synthesized unpyrolyzed YSZ powder was air plasma sprayed in order to produce segmentation crack TTBCs. The microstructure and hardness of the deposits were then compared with those of the conventional TTBCs and dense vertically cracked (DVC)TTBCs. In this regard, spraying parameters were optimized to achieve deposits with the appropriate amount of unpyrolyzed particles in them to assist inducing vertical cracks in the deposited layers. The effect of the unpyrolyzed particles on microstructure, porosity, and microhardness of plasma sprayed coatings were also evaluated and compared. The new fabricated coating showed a bimodal structure combining non-molten sub-micron size particles and conventional splats along with segmentation cracks with higher amount of porosity and lower hardness compared to those of the DVC coatings. The results implied that, depositing unpyrolyzed powder by APS, as a new approach for achieving segmentation crack TTBCs, is very promising.

The Effects of Thick Thermal Barrier Coatings on Low-Temperature Combustion

<div class="section abstract"><div class="htmlview paragraph">An experimental study was conducted on a Ricardo Hydra single-cylinder light-duty diesel research engine. Start of Injection (SOI) timing sweeps from -350 deg aTDC to -210 deg aTDC were performed on a total number of five pistons including two baseline metal pistons and three coated pistons to investigate the effects of thick thermal barrier coatings (TBCs) on the efficiency and emissions of low-temperature combustion (LTC). A fuel with a high latent heat of vaporization, wet ethanol, was chosen to eliminate the undesired effects of thick TBCs on volumetric efficiency. Additionally, the higher surface temperatures of the TBCs can be used to help vaporize the high heat of vaporization fuel and avoid excessive wall wetting. A specialized injector with a 60° included angle was used to target the fuel spray at the surface of the coated piston. Throughout the experiments, the equivalence ratio, ϕ, was maintained constant at 0.4; the combustion phasing was consistently matched at 6.8 ± 0.4 deg aTDC. It can be concluded that the thick TBC cases achieved 1 to 2 percentage points improvement in combustion efficiency, and generally, a ~2 percentage points increase in indicated engine efficiency. It is also noticed that applying a dense top sealing layer to the TBC further improves the UHC emissions compared to the TBC coated piston with an unsealed surface. From the heat release analysis, it can be concluded that the TBCs have no significant impact on the heat release process and knock intensity while matching the combustion phasing; however, it reduces the intake temperature requirement by up to 20 K. The exhaust gas temperatures were expected to increase for the TBC cases, but the expected increase in exhaust temperature was not conclusive from the results observed in this study.</div></div>

Measurement on the thermal barrier ability of ceramic coatings in a flame thermal shock tester

Ceramic materials are widely used at high temperatures due to their low thermal conductivity. Thermal barrier coatings (TBCs) have been applied in hot sections in industrial gas turbines and air engines. The measurement of the thermal barrier ability of the TBCs is very important for coating property evaluation, that can be done in hot gases with temperature gradient through the coatings. In this study, a flame thermal shock tester was used for such investigation. Thick TBC, containing a MCrAlY bond coat and a YSZ top coat, was sprayed onto a superalloy substrate by air plasma spray (APS) process. In the test, hot flame impacted on the top coat surface with the temperature controlled by an infrared thermometer. A thermocouple was attached onto the backside of the substrate to measure the backside temperature. Therefore, the temperature gradient in the TBC can be evaluated. The thermal barrier ability of the TBCs in different back cooling rate was studied.

Effect of segmented cracks on TGO growth and life of thick thermal barrier coating under isothermal oxidation conditions

This paper is devoted to a comparative study on the isothermal oxidation of thick thermal barrier coating (TTBC) with and without segmented cracks produced by atmospheric plasma spray (APS) process. Accordingly, the growth of thermally grown oxide (TGO) and its effect on the degradation of the coating were investigated. Thick top coat in both segmented crack and conventional thick TBC reduced the double layered TGO growth rate slightly. The segmented crack thick TBC demonstrated longer isothermal oxidation life in comparison with that of the conventional thick TBC at 1100 °C. The dominant failure mechanism was spallation due to lateral cracking within the TGO and/or within TBC near the TGO layer, called mixed failure. Stress, and consequently strain, induced on the TTBC due to progressive TGO growth, seems to be primarily responsible for the crack initiation and propagation leading to the coating failure. Increment of elastic energy stored within the top coat due to the increasing of TGO thickness, finally causes thick thermal barrier coating failure in high temperature isothermal oxidation.

Behavior of yttria-stabilized zirconia (YSZ) during laser direct energy deposition of an Inconel 625-YSZ cermet

Thermal barrier coatings (TBC) are regularly used today to protect and extend the service life of several superalloys which are extensively used in high temperature applications. The existing TBCs are typically between 0.1 to 0.5 mm in thickness, are deposited on metal substrates using plasma spray or electron beam vapor deposition, and can reduce temperatures at the substrate surface by up to 300 °C. For greater temperature reductions there is a need for thicker TBCs. The building of thick TBCs has to date been stymied by poor adhesion, and cracking during deposition. It has been suggested that a functionally graded approach may reduce the residual stresses which result in these defects. To date there have been few reports on the deposition of ceramic or cermet coatings using laser AM and none have reported on the phase stability of ceramic particles post-deposition. This paper is a first report on the phase stability of ceramic particles following the compositional segregation of elements during deposition using a powder feed additive manufacturing process. Functionally graded (FG), thick TBCs (>3 mm) consisting of Inconel 625 (IN625) and yttria-partially stabilized zirconia (8YSZ) were deposited on an A516 steel substrate via laser direct energy deposition (LDED). Good interfaces were observed between the bond coat (BC) and first cermet layer and between the graded cermet layers. However, cermet layers deposited with 10 wt.% or more YSZ developed a thin layer of YSZ on the surface. The thin layer of YSZ greatly hindered additional deposition of new cermet layers. In cermet layers that did exhibit good interfaces, fine, re-solidified, YSZ particles were homogenously distributed within the Inconel 625 matrix. The YSZ particles exhibited a tetragonal lattice structure and were depleted of yttrium. In contrast, the thin YSZ layer formed on a cermet surface showed no yttrium depletion.

Crack Propagation and Effect of Mixed Oxides on TGO Growth in Thick La–Gd–YSZ Thermal Barrier Coating

Thick thermal barrier coatings (TBCs) are the main choice in the aviation industry due to their ability to handle elevated temperature exposure in turbines. However, the efficacy of thick TBCs has not been adequate. This study presents a highly durable, thick top-coat (TC) of Lanthanum–gadolinium–yttria stabilized zirconia (La–Gd–YSZ) on high-velocity oxygen fuel (HVOF)-bond coat (HVOF-BC). Crack propagation was quantitatively assessed using a three-dimensional (3D) measuring laser microscope due to higher reliability in calculating the actual crack length of TBC. The findings revealed the HVOF-BC is highly durable with intact structural composition, while the conventional TBC of atmospheric plasma spraying (APS) bond coat (APS-BC) of the same composition and thickness with identical TC was detached at a crack-susceptible zone. The significant enhancement in HVOF-BC is due to the low mixed-oxides growth rate in thermally grown oxide (TGO) with a uniform and dense protective layer of stable Al2O3 which reduces crack propagation. Meanwhile, the failure in APS-BC can be attributed to the high TGO growth rate and thickness with segmented and unstable Al2O3. Furthermore, detrimental mixed oxides such as spinel Ni(Cr,Al)2O4 and NiO lead to disastrous horizontal and compressive cracks. To that end, we study the effect of TGO growth and crack propagation on HVOF-BC TBCs using APS-BC TBCs as a reference.

Turbine blade temperature error as measured with an optical pyrometer under different wavelengths and blade TBC thickness.

The optical pyrometer is a widely used instrument for measuring the temperature of gas turbine blade targets. However, one of the limitations of this instrument is the measurement error caused by reflected radiation from the high-temperature surrounding environment. This paper presents an analysis of such measurement error with consideration of a wavelength detection range of 2.5 to 22μm with blade thermal barrier coatings (TBCs) ranging from 18 to 279μm. Surface temperature distributions were simulated using the software ANSYS CFX. Radiation heat transfer was calculated based on discretized triangular surface elements. The variation characteristics of relative temperature error under different wavelengths and TBC thicknesses were obtained. The results obtained are well suited to provide theoretical guidance for choosing the wavelength of a pyrometer when measuring blade temperature with different TBC thickness, and can also be used to provide a method for estimating and correcting the temperature error.

Thermo-mechanical behavior of gas turbine blade equipped with cooling ducts and protective coating with different thicknesses

In this paper, the effects of Thermal Barrier Coating (TBC) thickness on temperature and stress distribution over the blade body are investigated. TBC acts like an insulation layer that increases the temperature gradient between the hot gases and the blade body. For this purpose, a 3D model of the blade body and TBC is created. Material of the substrate is considered as temperature-dependent Elastoplastic material, which its plasticity behavior is extracted point by point from the stress-strain curve. TBC is modeled as an elastic body, and the boundary conditions are applied as heat transfer coefficient. The significant point is that while the TBC thickness increases, the substrate thickness decreases respectively so that the total geometry of the whole blade remains constant in order to keep its aerodynamic behavior unchanged. Results show that increasing TBC thickness, affects significantly on the temperature distribution of the blade as some regions its surface experience a 100 °C collapse in temperature by increasing TBC thickness from 100 to 500 μm. In addition, the temperature of coolant which emerges from the top of the blade, is affected by TBC thickness, especially in the microholes near the leading and the trailing edges. Using stress evaluation, the critical region near the blade surface, which can be considered as an eligible point for crack nucleation, can be investigated. Results show that increasing TBC thickness from 100 to 500 μm, leads to 40 times decrease in the equivalent plastic strain.

Modeling Temperature Distributions in Thermal Barrier Coatings with Various Thicknesses

The geometric model of thermal barrier coatings (TBCs) was established. Two cases based on the standard thickness of the ceramic layer existed. These were the steps of TBCs thickness were being higher than the standard layer and those of lower than standard layer. The heat transfer processes of these two cases were simulated with the ANSYS software. The change process of thermal effusivity was analyzed in the two cases and the coating thickness differences effect on the surface temperature distributions of TBCs was analyzed through the time course curves of temperature difference. Moreover, the difficulty of detection for these two cases with infrared nondestructive testing was discussed according to maximum temperature difference and the maximum temperature contrast ratio. The result demonstrated that all curves of thermal effusivity with various thickness differences coincided with each other at the initial and longer times, where the ceramic layer thickness was lower than the standard layer. This was more easily detectable compared to the higher thickness and the maximum temperature contrast ratio or the maximum temperature difference increased as the coating thickness difference increased.

Residual stress measurement of Sic fiber/YSZ composite thermal barrier coating by micro-Raman spectroscopy

Residual stress distribution in Sic fiber/YSZ composite thermal barrier coating (TBC) on a stainless substrate has been measured by micro-Raman spectroscopy. Stress-spectroscopic coefficient was calibrated on a independent TBC layer. The coefficient for all TBC system is Σ=33.92cm-1Gpa-1. The stress measurement along the TBC thickness shows compressive stress distribution is decrease progressively from substrate/top coat interface to TBC surface. And the fiber can effectively relaxing the residual stress of composite coating.