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1.
Maurice Gell Jiwen Wang Rishi Kumar Jeffery Roth Chen Jiang Eric H. Jordan 《Journal of Thermal Spray Technology》2018,27(4):543-555
Gas-turbine engines are widely used in transportation, energy and defense industries. The increasing demand for more efficient gas turbines requires higher turbine operating temperatures. For more than 40 years, yttria-stabilized zirconia (YSZ) has been the dominant thermal barrier coating (TBC) due to its outstanding material properties. However, the practical use of YSZ-based TBCs is limited to approximately 1200 °C. Developing new, higher temperature TBCs has proven challenging to satisfy the multiple property requirements of a durable TBC. In this study, an advanced TBC has been developed by using the solution precursor plasma spray (SPPS) process that generates unique engineered microstructures with the higher temperature yttrium aluminum garnet (YAG) to produce a TBC that can meet and exceed the major performance standards of state-of-the-art air plasma sprayed YSZ, including: phase stability, sintering resistance, CMAS resistance, thermal cycle durability, thermal conductivity and erosion resistance. The temperature improvement for hot section gas turbine materials (superalloys & TBCs) has been at the rate of about 50 °C per decade over the last 50 years. In contrast, SPPS YAG TBCs offer the near-term potential of a > 200 °C improvement in temperature capability. 相似文献
2.
H.K. Sezer L. Li S. Leigh 《International Journal of Machine Tools and Manufacture》2009,49(14):1126-1135
Laser fabrication of cooling holes in certain parts of the aero-engine components involves percussion or trepan drilling at acute angles to the surface. These parts are often covered with plasma sprayed ceramic thermal barrier coatings (TBC) to protect them from reaching excessive temperatures in hot engine environments. Delamination of the TBC is the main problem of laser drilling acute angled holes in the coated components. The present study investigates a novel technique enabling to drill through thermal barrier-coated materials without delamination. The technique is based on the control of the melt flow trajectories and impact angle on the hole walls utilizing a secondary gas jet. Delamination-free laser-drilled holes inclined at 30° to the workpiece surface have been demonstrated. Finite volume-based numerical modelling of melt flow during the drilling process was developed to understand the effect of secondary jet in the prevention of delamination. 相似文献
3.
Satyapal Mahade Nicholas Curry Stefan Björklund Nicolaie Markocsan Per Nylén Robert Vaßen 《Journal of Thermal Spray Technology》2017,26(1-2):108-115
7-8 wt.% Yttria-stabilized zirconia (YSZ) is the standard thermal barrier coating (TBC) material used by the gas turbines industry due to its excellent thermal and thermo-mechanical properties up to 1200 °C. The need for improvement in gas turbine efficiency has led to an increase in the turbine inlet gas temperature. However, above 1200 °C, YSZ has issues such as poor sintering resistance, poor phase stability and susceptibility to calcium magnesium alumino silicates (CMAS) degradation. Gadolinium zirconate (GZ) is considered as one of the promising top coat candidates for TBC applications at high temperatures (>1200 °C) due to its low thermal conductivity, good sintering resistance and CMAS attack resistance. Single-layer 8YSZ, double-layer GZ/YSZ and triple-layer GZdense/GZ/YSZ TBCs were deposited by suspension plasma spray (SPS) process. Microstructural analysis was carried out by scanning electron microscopy (SEM). A columnar microstructure was observed in the single-, double- and triple-layer TBCs. Phase analysis of the as-sprayed TBCs was carried out using XRD (x-ray diffraction) where a tetragonal prime phase of zirconia in the single-layer YSZ TBC and a cubic defect fluorite phase of GZ in the double and triple-layer TBCs was observed. Porosity measurements of the as-sprayed TBCs were made by water intrusion method and image analysis method. The as-sprayed GZ-based multi-layered TBCs were subjected to erosion test at room temperature, and their erosion resistance was compared with single-layer 8YSZ. It was shown that the erosion resistance of 8YSZ single-layer TBC was higher than GZ-based multi-layered TBCs. Among the multi-layered TBCs, triple-layer TBC was slightly better than double layer in terms of erosion resistance. The eroded TBCs were cold-mounted and analyzed by SEM. 相似文献
4.
目的 探究重型燃机喷嘴壳体及遮热板热障涂层剥落机制,为该部件的全寿命管理提供参考。方法 采用等离子喷涂方法,分别制备以06Cr25Ni20不锈钢和Hastelloy X合金为基材的热障涂层试验件,并结合水淬热冲击表征方法与瞬态热力耦合仿真方法,表征热障涂层水淬后的剥落状态,获得热障涂层残余剪应力的分布状态随基材和服役工况的变化行为,揭示热障涂层在多层热失配工况下的剥落机制。结果 在水淬热冲击条件下,2种不同基材的热障涂层试验件表现出类似的剥落行为,但由于基材热膨胀系数的差异,以06Cr25Ni20不锈钢为基材的热障涂层的残余剪应力(70.1 MPa)比Hastelloy X合金基材的热障涂层(52.7 MPa)更大,热冲击寿命更短。在梯度温度载荷下,2种不同基材热障涂层试验件的失效模式不同,前者的最大残余剪应力为39.2 MPa,后者为25.7 MPa。结论 在2种温度载荷下,以Hastelloy X合金为基材的热障涂层具有较低的残余应力和较长的服役寿命。此外,水淬热冲击可以快速表征热障涂层的寿命行为,但其失效模式与实际梯度温度载荷下的失效模式仍有一定区别。 相似文献
5.
William J. Brindley 《Journal of Thermal Spray Technology》1997,6(1):3-4
Thermal Barrier Coatings (TBCs) in current gas turbine engines routinely deliver metal tempera-ture reductions of 50 to 80°C
under normal conditions and as much as 140°C temperature reduc-tions in hot spots (Ref 1). This temperature reduction can
be used to lower metal component tem-peratures under constant operating conditions to achieve longer life, or to increase
the performance of the engine through higher operating temperatures while maintaining constant life of the component, as indicated
by the horizontal arrows in Fig. 1. A middle road of longer life and increased engine performance/efficiency is also possible.
The choice of how to use the thermal benefits derived from TBCs is critical, especially if the intent is to follow the high
economic pay-off path of increasing the operating temperatures to increase engine efficiency. In this case, large increases
in operating temperature and engine efficiency are possible with the insulating capabil-ity of TBCs. The problem is that if
the temperatures are increased to take full advantage of the TBC insulating ability, and a large frac-tion of the coating
spalls, the remaining bare metallic component would be subjected to high temperatures and unacceptably rapid deg-radation
(Fig. 1). Obviously, the risk of coating failure must be balanced against the benefit of coating use. 相似文献
6.
Thermal barrier coatings (TBCs) have been used in high-thrust aircraft engines for many years to pro-vide thermal protection
and increase engine efficiencies. TBC life requirements for aircraft engines are typically less than those required for industrial
gas turbines. This paper describes current and future ap-plications of TBCs in industrial gas turbine engines. Early testing
and applications of TBCs are reviewed. Areas of concern from the engine designer’s and materials engineer’s perspective are
identified and evaluated. This paper focuses on the key factors that are expected to influence utilization of TBCs in ad-vanced
industrial gas turbine engines. It is anticipated that reliable, durable, and highly effective coating systems will be produced
that will ultimately improve engine efficiency and performance. 相似文献
7.
8.
《Surface & coatings technology》2001,135(2-3):188-195
In gas turbines, thermal barrier coatings (TBCs) applied by air plasma spraying are widely used to reduce the temperature in hot components. The TBC allows higher gas temperature and/or reduces the need for internal cooling in the hot components, thus increasing the efficiency of the gas turbine. Spallation is a common failure mechanism of TBC and occurs after a critical number of thermal cycles, when the alumina layer has grown to a critical thickness. The influence of the growing alumina layer and the top/bond-coat interface roughness in the TBC has been investigated. The primary goal was to identify failure mechanisms that can be incorporated into a life model of the TBC, and to increase the understanding of the delamination process in the TBC. A new formulation of alumina growth is proposed, in which the swelling strains caused by the volumetric increase during alumina growth depends on the stress state. The alumina growth model is used in 3D FE thermal cycling simulations of a TBC in which the thermal cycle time is long enough to characterize a typical cycle of a gas turbine. From the simulations, the growing alumina layer is observed to be one failure mechanism of the TBC. Without an alumina layer in the model, high delamination stress is observed at room temperature, above ridges of the top/bond-coat interface in the top coat. When the alumina is growing, the point of maximum delamination stress is moved towards the valleys. When the thickness of the alumina layer has grown to approximately 8–10 μm, positive delamination stress is found above the valleys in the top coat. The movement of the positive delamination stress region can explain why a delamination crack develops, which will cause spallation of the TBC during shutdown to room temperature. 相似文献
9.
In-Hwan Shin Jae-Mean Koo Chang-Sung Seok Sung-Ho Yang Tack-Woon Lee Bum-Soo Kim 《Surface & coatings technology》2011
Plasma-sprayed thermal barrier coatings (TBCs) are applied to protect the blades of a gas turbine system from high-temperature gas and to lower the surface temperature of the blades. The failure of TBC is directly connected to the failure of the blades because the spallation of a ceramic layer leads to the acceleration of local corrosion and oxidation at the location of failure. Therefore, the spallation life of TBC is very important in the evaluation of the reliability of a gas-turbine blade.In this study, thermal fatigue tests were performed at 1100 °C and 1151 °C. Then, c-scanning and bond strength tests were performed for TBC specimens that were thermally aged by thermal fatigue tests. From the results, an empirical equation based on the ratio of the delamination area and the thermal cycle number was presented and the spallation life of a TBC specimen could be roughly estimated using the relationship between the delaminated area and the number of cycles. 相似文献
10.
R. Wellman G. Whitman J.R. Nicholls 《International Journal of Refractory Metals and Hard Materials》2010,28(1):124-132
Over the last decade a significant amount of research has been conducted into the durability of thermal barrier coatings (TBCs) focusing mainly on issues of oxidation, erosion and foreign object damage (FOD). However, as the performance and durability of TBCs has improved the temperatures at which they operate has increased. This increase in temperature has resulted in another lifing issue for EB PVD TBCs, namely that of CMAS attack. Calcium–magnesium–alumino-silicate (CMAS) attack occurs when atmospheric dust that has deposited on the surface of turbine blades melts and wicks into the columns of the TBC. This occurs at temperatures above 1240–1260 °C and results in the degradation of the columnar microstructure of the TBCs. Due to the fact that TBCs operate in a temperature gradient CMAS only infiltrates part of the coating before solidifying.There are a number of issues associated with CMAS attack, both chemical and mechanical. From a chemical point of view CMAS attack of electron beam (EB) physical vapour deposited (PVD) TBCs can be considered as a form of corrosion; when there is a lot of excess CMAS on the surface of a coated component Yttria diffuses out of the TBC into the molten CMAS resulting in a t′ to monoclinic phase transformation in the yttria stabilised zirconia (YSZ), CMAS attack also results in localised melting and subsequent re-precipitation of the coating resulting in a loss of the defined columnar microstructure. While from a mechanical point of view the CMAS, once re-solidified, reduces the strain compliance of the EB PVD and can result in spallation of the TBC on cooling. Furthermore, current studies have indicated that small amount of CMAS infiltration significantly increases the erosion rate of EB PVD TBCs.This paper covers various aspects of CMAS attack of EB PVD TBCs, specifically looking at minimum levels of CMAS required to initiate damage, as well as investigating it from an erosion–corrosion perspective. 相似文献
11.
PVD thermal barrier coating applications and process development for aircraft engines 总被引:2,自引:0,他引:2
D. V. Rigney R. Viguie D. J. Wortman D. W. Skelly 《Journal of Thermal Spray Technology》1997,6(2):167-175
Thermal barrier coatings (TBCs) have been developed for application to aircraft engine components to improve service life
in an increasingly hostile thermal environment. The choice of TBC type is related to the component, intended use, and economics.
Selection of electron beam physical vapor deposition proc-essing for turbine blade is due in part to part size, surface finish
requirements, thickness control needs, and hole closure issues. Process development of PVD TBCs has been carried out at several
different sites, including GE Aircraft Engines (GEAE). The influence of processing variables on microstructure is dis-cussed,
along with the GEAE development coater and initial experiences of pilot line operation. 相似文献
12.
13.
During the last decade, research efforts were devoted to the development and manufacturing of ceramic thermal barrier coatings (TBCs) on turbine parts because the traditional turbine materials have reached the limits of their temperature capabilities. TBCs have been widely used in hot-section metal components in gas turbines either to increase the inlet temperature with a consequent improvement of the efficiency or to reduce the requirements of the cooling air. There are several ceramics that have been evaluated as TBC materials, and lanthanum zirconate (LZ) is one of the most promising among them. The properties namely high-melting point, phase stability up to its melting point, low thermal conductivity, low sintering ability and oxygen-non transparent make the LZ a potential TBC material for high-temperature applications. However, the production methods used to synthesise LZ are highly time consuming and the powder is not commercially available. Hence, in this investigation an attempt was made to synthesise, spheroidize and spray deposit LZ material using thermal plasma process. This paper illustrates the effectiveness of thermal plasma as a major materials processing technique. Suitable characterization techniques have been used to study the material modifications after respective plasma processing exposures. 相似文献
14.
T. Koomparkping S. Damrongrat P. Niranatlumpong 《Journal of Thermal Spray Technology》2005,14(2):264-267
A thermal barrier coating (TBC) is applied on a surface of a gas turbine blade to provide a thermal barrier and oxidation
resistant properties for the components. The ability to resist oxidation of the coating arises from the self-healing, protective
Al2O3 scale on top of the bondcoat, which is formed during service. However, if Al depletion occurs within the bondcoat, the protective
scale will lose its self-healing ability, and hence, its oxidation-resistant property. This paper investigated the depletion
of Al within the bondcoat by studying the microstructure of the bondcoat on a gas turbine blade after it has been in 4000
h service at 1200 °C. The results showed that Al depletion had occurred at different levels throughout the turbine blade.
In the area where Al depletion had not yet occurred, precipitation of an Al-rich phase was detected. Most of the Al was contained
within this phase, leaving only small amount of Al in the surrounding matrix. A well-defined boundary was observed between
the depleted and non-depleted regions. 相似文献
15.
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
16.
Thermal barrier coatings have been widely used in gas turbine engines in order to protect the substrate metal alloy against high temperature and to enhance turbine efficiency. To monitor thermal barrier coating (TBC) integrity over its lifetime, the detection of top coat (TC) and thermally grown oxide (TGO) thicknesses was carried out using a microwave non-destructive technique. The results showed a good resolution of 1° change in phase for 15 μm TC thickness when a rectangular waveguide operating at relatively high frequency was applied. The phase of the reflection coefficient at the interface of TC and waveguide varies for different TGO and TC thicknesses. Therefore, measuring the phase of the reflection coefficient enables us to accurately calculate these thicknesses. Finally, a theoretical analysis was used to evaluate the reliability of the experimental results. 相似文献
17.
《International Heat Treatment & Surface Engineering》2013,7(3):108-113
AbstractA breakthrough in the area of PVD/CVD coating technologies, as in other surface engineering technologies, requires not only technical innovation but also innovative technological and organisational support. The cohesion of these diverse areas forms a basis for obtaining theoretical and physical models, which give rise to prototypes for the rapid application of breakthrough solutions. Mechanisms and structures aimed at reaching breakthrough research objectives are presented, taking as an example the investigation and application of new materials, particularly using surface engineering PVD plasma technologies. The advanced technology of thermal barrier coatings (TBC) is described and the associated process development, including the design and construction of a unique hybrid device for TBC creation, are presented. By means of this example, a combination of breakthrough and incremental research is explored and a real path for balancing research and knowledge transfer, leading to innovative solutions and technologically advanced product application, is demonstrated. 相似文献
18.
C. Y. Su C. P. Chou B. C. Wu W. C. Lih 《Journal of Materials Engineering and Performance》1997,6(5):619-627
Plasma transferred arc welding (PTA) has been considered a promising process to restore worn areas of land-based gas turbine
blades and vanes.
The objective of this investigation was to study the effect of PTA welding on the repairing of IN-738LC superalloy components.
Tensile tests were conducted on specimens welded with various combinations of parameters. Room temperature, 760 °C, and 980
°C were selected as tensile test temperatures. High-temperature phase transformed, during solidification, were identified
by differential thermal analysis (DTA). The weld-pool shapes and microstructures of welded specimens prepared by various welding
parameters were evaluated by optical metallography (OM), a scanning electron microscope (SEM) equipped with energy dispersive
x-ray spectrometer (EDS), and microhardness testing.
Results of this study showed that PTA welded specimens exhibited 96% nominal tensile strength of IN738LC base materials. Specimen
failure was observed predominantly in the base materials instead of in the heat-affected zone (HAZ) for gas tungsten arc weld
(GTAW) repair weldments. IN-738LC is considered susceptible to weld cracking during fusion welding; however, using a low-input
heat repair welding process (PTA), cracking susceptibility could be minimized by the optimized welding parameters. 相似文献
19.
Pratt & Whitney has accumulated more than three decades of experience with thermal barrier coatings (TBCs). These coatings
were originally developed to reduce surface temperatures of combustors of JT8D gas turbine engines to increase the thermal
fatigue life of the components. Continual improvements in de-sign, processing, and properties of TBCs have extended their
applications to other turbine components, such as vanes, vane platforms, and blades, with attendant increases in performance
and component du-rability. Plasma-spray-based generation I (Gen I) combustor TBCs with 7 wt % yttria partially stabilized
zirconia deposited by air plasma spray (APS) on an APS NiCoCrAlY bond coat continues to perform ex-tremely well in all product
line engines. Durability of this TBC has been further improved in Gen II TBCs for vanes by incorporating low-pressure chamber
plasma-sprayed NiCoCrAl Y as a bond coat. The modi-fication has improved TBC durability by a factor of 2.5 and altered the
failure mode from a “black fail-ure” within the bond coat to a “white failure” within the ceramic.
Further improvements have been accomplished by instituting a more strain-tolerant ceramic top layer with electron beam/physical
vapor deposition (EB-PVD) processing. This Gen III TBC has demonstrated exceptional performance on rotating airfoils in high-thrust-rated
engines, improving blade durability by three times through elimination of blade creep, fracture, and rumpling of metallic
coatings used for oxi-dation protection of the airfoil surfaces. A TBC durability model for plasma-sprayed as well as EB-PVD
systems is proposed that involves the accumulation of compressive stresses during cyclic thermal expo-sure. The model attempts
to correlate failure of the various TBCs with elements of their structure and its degradation with thermocyclic exposure. 相似文献
20.
Molybdenum silicide based materials and their properties 总被引:2,自引:0,他引:2
Z. Yao J. Stiglich T. S. Sudarshan 《Journal of Materials Engineering and Performance》1999,8(3):291-304
Molybdenum disilicide (MoSi2) is a promising candidate material for high temperature structural applications. It is a high melting point (2030 °C) material
with excellent oxidation resistance and a moderate density (6.24 g/cm3). However, low toughness at low temperatures and high creep rates at elevated temperatures have hindered its commercialization
in structural applications. Much effort has been invested in MoSi2 composites as alternatives to pure molybdenum disilicide for oxidizing and aggressive environments. Molybdenum disilicide-based
heating elements have been used extensively in high-temperature furnaces. The low electrical resistance of silicides in combination
with high thermal stability, electronmigration resistance, and excellent diffusion-barrier characteristics is important for
microelectronic applications. Projected applications of MoSi2-based materials include turbine airfoils, combustion chamber components in oxidizing environments, missile nozzles, molten
metal lances, industrial gas burners, diesel engine glow plugs, and materials for glass processing. In this paper, synthesis,
fabrication, and properties of the monolithic and composite molybdenum silicides are reviewed. 相似文献