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1.
Ann Bolcavage Albert Feuerstein John Foster Peter Moore 《Journal of Materials Engineering and Performance》2004,13(4):389-397
Various methods of thermal shock testing are used by aircraft and industrial gas turbine engine (IGT) manufacturers to characterize
new thermal barrier coating systems in the development stage as well as for quality control. The cyclic furnace oxidation
test (FCT), widely used in aircraft applications, stresses the ceramic/bondcoat interface, predominantly through thermally
grown oxide (TGO) growth stress. The jet engine thermal shock (JETS) test, derived from a burner rig test, creates a large
thermal gradient across the thermal barrier coating (TBC), as well as thermomechanical stress at the interface. For IGT applications
with long high-temperature exposure times, a combination of isothermal preoxidation and thermal shock testing in a fluidized
bed reactor may better represent the actual engine conditions while both types of stress are present. A comparative evaluation
of FCT, JETS, and a combined isothermal oxidation and fluidized bed thermal shock test has been conducted for selected ceramic/bondcoat
systems. The results and the failure mechanisms as they relate to the TBC system are discussed. A recommendation on the test
method of choice providing best discrimination between the thermal shock resistance of the ceramic layer, the ceramic/bondcoat
interface, and even substrate related effects, is given.
This paper was presented at the 2nd International Surface Engineering Congress sponsored by ASM International, on September
15–17, 2003, in Indianapolis, Indiana, and appeared on pp. 520–29. 相似文献
2.
利用微弧氧化技术,在碱性硅酸盐电解液中对纯铝进行表面改性处理,制备均匀致密的陶瓷膜。利用扫描电子显微镜(SEM)观察氧化陶瓷膜表面形貌及横截面组织结构,利用纳米压入硬度测试仪测量陶瓷膜的显微硬度和杨氏模量的分布,运用电化学方法测量陶瓷膜的耐腐蚀性能。结果表明,铝合金微弧氧化陶瓷膜的表面硬度高达25.3GPa,纳米硬度和杨氏模量在陶瓷膜的横截面分布相似,从膜基结合处向膜层表面呈下降趋势。从极化曲线中的腐蚀电势和腐蚀电流来看,微弧氧化处理后,纯铝的抗腐蚀能力得到很大的提高。 相似文献
3.
本文通过在计算机中建立航空发动机叶片的工作环境,进而模拟在飞行状态下叶片表面涂敷的陶瓷热障涂层的受力行为,获得了陶瓷涂层在热气动载荷作用下应力场分布,并得出应力场分布与涂层结构和叶片几何形状及与承受的载荷之间的关系,提出了进一步提高陶瓷热障涂层的使用寿命的途径。 相似文献
4.
目的采用低温超音速等离子喷涂(LT-HVOF)在镍基高温合金基体(K417)上制备了NiCoCrAlYTa粘结层,使用大气等离子喷涂(APS)在粘结层上制备了纳米7%Y_2O_3-ZrO_2(7YSZ)陶瓷涂层,以获得温度梯度热循环下纳米陶瓷层的结构演变机制。方法通过燃气热冲击实验仪对热障涂层模拟真实服役条件下温度梯度热循环的工作环境,采用一维稳态热传导模型计算了热障涂层中各涂层界面的温度,探讨了在热驱动作用下等径晶粒和非等径晶粒的扩散长大机制。结果热循环次数为40次时,涂层近表面出现了烧结致密化现象,而陶瓷层底部涂层保持原来的结构。热循环次数增加到460次时,整个陶瓷层断面都发生了烧结致密化现象。结论温度是涂层烧结致密化的主导因素。涂层中当等大晶粒接触形成弯曲颈时,由于弯曲颈只受水平方向静压力作用,晶粒中原子扩散速率慢,导致晶粒长大速率较慢;而当非等大晶粒接触形成弯曲颈时,在晶粒接触弯曲颈处存在一偏大晶粒方向的剪切力,其导致晶粒向弯曲颈扩散速率增加,晶粒长大速率较快。 相似文献
5.
Zhe LU Min-Sik KIM Sang-Won MYOUNG Je-Hyun LEE Yeon-Gil JUNG In-Soo KIM Chang-Yong JO 《中国有色金属学会会刊》2014
The thermal stability and failure mechanism of thick thermal barrier coatings (TBCs) with and without vertical type cracks were investigated through the cyclic thermal exposure and thermal-shock tests. The TBC systems with thickness of about 2000 µm in the top coat were prepared by an air plasma spray (APS) on the bond coat of about 150 µm in thickness prepared by APS. The adhesive strength values of the as-prepared TBCs with and without vertical type cracks were determined to be 24.7 and 11.0 MPa, respectively, indicating the better interface stability in the TBC with vertical type cracks. The TBC with vertical type cracks shows a better thermal durability than that without vertical type cracks in the thermal cyclic exposure and thermal-shock tests. The hardness values of the as-prepared TBCs with and without vertical type cracks were found to be 6.6 and 5.3 GPa, respectively, which were increased to 9.5 and 5.5 GPa, respectively, after the cyclic thermal exposure tests. These results indicate that the vertical type cracks developed in the top coat are important in improving the lifetime performance of thick TBC in high temperature environment. 相似文献
6.
D. M. Nissley 《Journal of Thermal Spray Technology》1997,6(1):91-98
Analytical models for predicting ceramic thermal barrier coating (TBC) spalling life in aircraft gas tur-bine engines are
presented. Electron beam/physical vapor-deposited and plasma-sprayed TBC systems are discussed. An overview of the following
TBC spalling mechanisms is presented: (1) metal oxidation at the ceramic/metal interface, (2) ceramic/metal interface stresses
caused by radius of curvature and inter-face roughness, (3) material properties and mechanical behavior, (4) component design
features, (5) tem-perature gradients, (6) ceramic/metal interface stress singularities at edges and corners, and (7) object
impact damage. Analytical models for TBC spalling life are proposed based on observations of TBC spall-ing and plausible failure
theories. Spalling was assumed to occur when the imposed stresses exceed the material strength (at or near the ceramic/metal
interface). Knowledge gaps caused by lack of experimen-tal evidence and analytical understanding of TBC failure are noted.
The analytical models are considered initial engineering approaches that capture observed TBC spalling failure trends. 相似文献
7.
Thermal barrier coatings (TBC) are extensively used to protect metallic components in applications where the operating conditions include aggressive environment at high temperatures. Isothermal oxidation degrades the performance of these coatings, so this work analyses the mechanical properties (Young's modulus, E, and hardness, H) of TBC and its evolution after thermal exposure in air. ZrO2(Y2O3) top coat and NiCrAlY bond coating were air plasma sprayed onto an Inconel 600 Ni base alloy. The TBC were isothermally oxidized in air at 950 °C and 1050 °C for 72, 144 and 336 h. Depth sensing indentation tests were carried out on the ceramic coating to evaluate E and H in the as-sprayed materials and after isothermal oxidation. An approach based on multiple tests at different loads was used to determine size independent apparent E an H. These mechanical properties, measured perpendicular to the surface, clearly decreased after isothermal oxidation as a consequence of microcracking within the ceramic coating. 相似文献
8.
Preparation of micro-arc oxidation coatings on magnesium alloy and its thermal shock resistance property 总被引:2,自引:1,他引:2
JIANG Zhaohua ZENG Xiaobin and YAO Zhongping Department of Applied Chemistry Harbin Institute of Technology Harbin China 《稀有金属(英文版)》2006,25(3):270-273
1. Introduction Due to their high specific strength, good electro-magnetic shielding characteristics, high damping characteristics, good cast ability, and excellent pol-ishing capability, magnesium alloys are extensively used in aeronautical, automobile, and electro- communication industries [1-3]. But magnesium has some disadvantages, such as low chemical stability, high negative electric potential, and low hardness, so it is necessary to use surface disposal to accommo-date the demand for re… 相似文献
9.
Gas turbines provide one of the most severe environments challenging material systems nowadays. Only an appropriate coating system can supply protection particularly for turbine blades. This study was made by comparison of properties of two different types of thermal barrier coatings (TBCs) in order to improve the surface characteristics of high temperature components. These TBCs consisted of a duplex TBC and a five layered functionally graded TBC. In duplex TBCs, 0.35 mm thick yittria partially stabilized zirconia top coat (YSZ) was deposited by air plasma spraying and ~0.15 mm thick NiCrAlY bond coat was deposited by high velocity oxyfuel spraying. ~0.5 mm thick functionally graded TBC was sprayed by varying the feeding ratio of YSZ/NiCrAlY powders. Both coatings were deposited on IN 738LC alloy as a substrate. Microstructural characterization was performed by SEM and optical microscopy whereas phase analysis and chemical composition changes of the coatings and oxides formed during the tests were studied by XRD and EDX. The performance of the coatings fabricated with the optimum processing conditions was evaluated as a function of intense thermal cycling test at 1100 °C. During thermal shock test, FGM coating failed after 150 and duplex coating failed after 85 cycles. The adhesion strength of the coatings to the substrate was also measured. Finally, it is found that FGM coating has a larger lifetime than the duplex TBC, especially with regard to the adhesion strength of the coatings. 相似文献
10.
Dongming Zhu James A. Nesbitt Charles A. Barrett Terry R. McCue Robert A. Miller 《Journal of Thermal Spray Technology》2004,13(1):84-92
Ceramic thermal barrier coatings (TBCs) will play an increasingly important role in advanced gas turbine engines due to their
ability to further increase engine operating temperatures and reduce cooling, thus helping achieve future engine low emission,
high efficiency, and improved reliability goals. Advanced multicomponent zirconia (ZrO2)-based TBCs are being developed using an oxide defect clustering design approach to achieve the required coating low thermal
conductivity and high-temperature stability. Although the new composition coatings were not yet optimized for cyclic durability,
an initial durability screening of the candidate coating materials was conducted using conventional furnace cyclic oxidation
tests. In this paper, furnace cyclic oxidation behavior of plasma-sprayed ZrO2-based defect cluster TBCs was investigated at 1163°C using 45 min hot-time cycles. The ceramic coating failure mechanisms
were studied using scanning electron microscopy (SEM) combined with x-ray diffraction (XRD) phase analysis after the furnace
tests. The coating cyclic lifetime is also discussed in relation to coating processing, phase structures, dopant concentration,
and other thermo-physical properties. 相似文献
11.
V. Teixeira M. Andritschky H. Gruhn W. Malléner H. P. Buchkremer D. Stöver 《Journal of Thermal Spray Technology》2000,9(2):191-197
ZrO2-7 wt.% Y2O3 plasma-sprayed (PS) coatings were applied on high-temperature Ni-based alloys precoated by physical vapor deposition with
a thin, dense, stabilized zirconia coating (PVD bond coat). The PS coatings were applied by atmospheric plasma spraying (APS)
and inert gas plasma spraying (IPS) at 2 bar for different substrate temperatures. The thermal barrier coatings (TBCs) were
tested by furnace isothermal cycling and flame thermal cycling at maximum temperatures between 1000 and 1150 °C. The temperature
gradients within the duplex PVD/PS thermal barrier coatings during the thermal cycling process were modeled using an unsteady
heat transfer program. This modeling enables calculation of the transient thermal strains and stresses, which contributes
to a better understanding of the failure mechanisms of the TBC during thermal cycling. The adherence and failure modes of
these coating systems were experimentally studied during the high-temperature testing. The TBC failure mechanism during thermal
cycling is discussed in light of coating transient stresses and substrate oxidation. 相似文献
12.
Recently, extensive efforts have been made to develop new thermal barrier coating (TBC) materials which can operate at temperatures
above 1523 K over a long term. In this article, LaTi2Al9O19 (LTA) was synthesized by solid-state reaction at 1773 K, and the mechanical properties of the LTA bulk were evaluated. The
microhardness is about 14 GPa, comparable to that of YSZ bulk, whereas the Young’s modulus is about 44 GPa, lower than the
value of YSZ. However, the fracture toughness of 0.8-1 MPa m1/2 is much lower than that of bulk YSZ. A double-ceramic-layer LTA/YSZ TBC structure was proposed and the TBC sprayed by plasma
spraying. Thermal cycling tests of the TBC specimens were performed at 1373 K with a dwell time of 10 min. The LTA remained
good stability with ZrO2 and Al2O3. However, the single layer LTA TBC was cracked at the LTA/bond coat interface after about 300 cycles, due to its poor thermal
shock resistance, while the YSZ TBC yielded a lifetime of about 1000 cycles. The LTA/YSZ TBC remained intact even after 3000
cycles, exhibiting a promising potential as new TBC materials. 相似文献
13.
Free-standing miniature beam specimens of thermal barrier coating (TBC) top coats were prepared by metal dissolution from high pressure turbine blades coated with TBC by electron beam physical vapour deposition (EBPVD) and thermally cycled to 1150 °C for various times. The beams comprised the yttria stabilized zirconia (YSZ) TBC and the thermally grown oxide (TGO) and their effective elastic modulus was measured using a miniaturized three-point bending test. The measured effective modulus was typically in the range of 10–22 GPa, with large specimen-to-specimen variations. The modulus increased with thermal exposure of the coated blades up to 85 cycles, but decreased for a larger number of cycles. The Young’s modulus of the YSZ layer alone was derived from the effective modulus of the composite beams (YSZ and TGO) by taking into account the contribution of the TGO. The derived Young’s modulus of the YSZ was in the range 5–10 GPa, and was verified independently by TGO residual stress measurement. Significant inelastic deformation was found to occur during the bending test when a relatively high load was applied and is speculated to be due to micro-fractures between columns in the YSZ. Specimens prepared from the concave part of the turbine blade were found to be approximately four times stiffer than those taken from a flat part of the blade, indicating that the modulus of the TBC is strongly dependent on the microstructure of the YSZ coating. 相似文献
14.
Thermal cycling behavior of plasma-sprayed thermal barrier coatings with various MCrAlX bond coats 总被引:1,自引:0,他引:1
The influence of bond coat composition on the spallation resistance of plasma-sprayed thermal barrier coatings (TBCs) on single-crystal
René N5 substrates was assessed by furnace thermal cycle testing of TBCs with various vacuum plasma spray (VPS) or air plasma-spray
(APS) MCrAlX (M=Ni and/or Co; and X=Y, Hf, and/or Si) bond coats. The TBC specimens with VPS bond coats were fabricated using
identical parameters, with the exception of bond coat composition. The TBC lifetimes were compared with respect to MCrAlX
composition (before and after oxidation testing) and MCrAlX properties (surface roughness, thermal expansion, hardness, and
Young’s modulus). The average TBC spallation lifetimes varied significantly (from 174 to 344 1 h cycles at 1150 °C) as a function
of bond coat composition. Results suggested a relationship between TBC durability and bond coat thermal expansion behavior
below 900 °C. Although there were only slight differences in their relative rates of cyclic oxidation weight gain, VPS MCrAlX
bond coats with better oxide scale adhesion provided superior TBC lifetimes. 相似文献
15.
S. Ahmaniemi J. Tuominen P. Vuoristo T. Mäntylä 《Journal of Thermal Spray Technology》2002,11(3):320-332
Zirconia-based 8Y2O3-ZrO2 and 22MgO-ZrO2 thick thermal barrier coatings (TTBC, 1000 μm), were studied with different sealing methods for diesel engine applications.
The aim of the sealing procedure was to improve hot corrosion resistance and mechanical properties of porous TBC coatings.
The surface of TTBCs was sealed with three different methods: (1) impregnation with phosphate-based sealant, (2) surface melting
by laser glazing, and (3) spraying of dense top coating with a detonation gun. The thicknesses of the densified top layers
were 50–400 μm, depending on the sealing procedure. X-ray diffraction (XRD) analysis showed some minor phase changes and reaction
products caused by phosphate-based sealing treatment and some crystal orientation changes and phase changes in laser-glazed
coatings. The porosity of the outer layer of the sealed coating decreased in all cases, which led to increased microhardness
values. The hot corrosion resistance of TTBCs against 60Na2SO4-40V2O5 deposit was determined in isothermal exposure at 650 °C for 200 h. Corrosion products and phase changes were studied with
XRD after the test. A short-term engine test was performed for the reference coatings (8Y2O3-ZrO2 and 22MgO-ZrO2) and for the phosphate-sealed coatings. Engine tests, duration of 3 h, were performed at the maximum load of the engine and
were intended to evaluate the thermal cycling resistance of the sealed coatings. All of the coatings passed the engine test,
but some vertical cracks were detected in the phosphate-sealed coatings. 相似文献
16.
This article addresses the predominant degradation modes and life prediction of a plasma-sprayed thermal barrier coating (TBC). The studied TBC system consists of an air-plasma-sprayed bond coat and an air-plasma-sprayed, yttria partially stabilized zirconia top layer on a conventional Hastelloy X substrate. Thermal shock tests of as-sprayed TBC and pre-oxidized TBC specimens were conducted under different burner flame conditions at Volvo Aero Corporation (Trollhättan, Sweden). Finite element models were used to simulate the thermal shock tests. Transient temperature distributions and thermal mismatch stresses in different layers of the coatings during thermal cycling were calculated. The roughness of the interface between the ceramic top coat and the bond coat was modeled through an ideally sinusoidal wavy surface. Bond coat oxidation was simulated through adding an aluminum oxide layer between the ceramic top coat and the bond coat. The calculated stresses indicated that interfacial delamination cracks, initiated in the ceramic top coat at the peak of the asperity of the interface, together with surface cracking, are the main reasons for coating failure. A phenomenological life prediction model for the coating was proposed. This model is accurate within a factor of 3. 相似文献
17.
An experimental rig based on the use of infrared quartz lamps has been developed to monitor the degradation mechanisms causing
failure of thermal barrier coatings (TBC) under thermal-cycling conditions. An acoustic emission (AE) technique monitored
these degradation mechanisms, and advanced signals processing identified the key parameters that classify the AE signals according
to the long-term behavior of the TBC. The AE technique enabled the localization of degradation sources inside the TBC with
a linear resolution of ∼5 mm by the use of two transducers fixed at both ends of the sample. Furthermore, sample zones of
high AE activity showed typical vertical cracks at the surface and delaminations at the interface between the ceramic and
the bond-coat layer. Vertical cracks were induced preferentially during the heating period of the thermal cycles when the
ceramic coating was in a tensile-stress state, while delaminations were induced during the cooling period when the TBC was
in a compressive-stress state. 相似文献
18.
The mechanical and tribological properties of thermal barrier coatings (TBCs) can be improved by means of a thermal treatment.
The evolution of the mechanical and tribological properties in a NiCr-ZrO2 TBC with different times of thermal treatment has been measured. In this work, scanning white light interferometry (SWLI)
is used to observe and quantify the ZrO2 wear damage. ZrO2 shows very poor light reflection, and a sputtering process over the coating has been made to achieve a proper light reflection
and make the use of SWLI possible.
It has been observed that thermal treatments at 1000 °C produce a decrease of the wear damage and an increase of hardness.
The ball-on-disk test and the wear mechanisms are described and include the intersplat delamination of the main wear process
in the as-sprayed coatings and thermally treated samples. The volume loss after 18 h at 1000 °C is 38% less than the as-sprayed
coating. The erosion test and hardness measures show the same evolution as the ball-on-disk test. 相似文献
19.
Technical and Economical Aspects of Current Thermal Barrier Coating Systems for Gas Turbine Engines by Thermal Spray and EBPVD: A Review 总被引:4,自引:1,他引:3
Albert Feuerstein James Knapp Thomas Taylor Adil Ashary Ann Bolcavage Neil Hitchman 《Journal of Thermal Spray Technology》2008,17(2):199-213
The most advanced thermal barrier coating (TBC) systems for aircraft engine and power generation hot section components consist
of electron beam physical vapor deposition (EBPVD) applied yttria-stabilized zirconia and platinum modified diffusion aluminide
bond coating. Thermally sprayed ceramic and MCrAlY bond coatings, however, are still used extensively for combustors and power
generation blades and vanes. This article highlights the key features of plasma spray and HVOF, diffusion aluminizing, and
EBPVD coating processes. The coating characteristics of thermally sprayed MCrAlY bond coat as well as low density and dense
vertically cracked (DVC) Zircoat TBC are described. Essential features of a typical EBPVD TBC coating system, consisting of
a diffusion aluminide and a columnar TBC, are also presented. The major coating cost elements such as material, equipment
and processing are explained for the different technologies, with a performance and cost comparison given for selected examples. 相似文献
20.
Anand A. Kulkarni Allen Goland Herbert Herman Andrew J. Allen Jan Ilavsky Gabrielle G. Long Francesco De Carlo 《Journal of Thermal Spray Technology》2005,14(2):239-250
Achieving control of the microstructure of plasma-sprayed thermal barrier coating (TBC) systems offers an opportunity to tailor
coating properties to demanding applications. Accomplishing this requires a fundamental understanding of the correlations
among processing, microstructure development, and related TBC properties. This article describes the quantitative characterization
of the microstructure of plasma-sprayed partially stabilized zirconia (PSZ) coatings by means of x-ray and neutron-scattering
imaging techniques. Small-angle neutron scattering, ultra-small-angle x-ray scattering, and x-ray microtomography were used
to characterize and visualize the nature and structure of the features in these material systems. In addition, the influence
of processing parameters on microstructure development is discussed along with thermal cycling effects on the pore morphology,
and their resultant influence of the porosity on the thermal conductivity and elastic modulus of plasma-sprayed PSZ TBCs. 相似文献