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1.
The present study uses plasma spray technology as a production process for the fabrication of free- stand-ing, near- net-
shaped NiAl components. Attention is especially focused on the in situ synthesis of NiAl. A new internal, dual powder injector
blade has been designed to improve the gun performance as well as the spray efficiency of the feedstock powder. The specific
role of the substrate (i.e., its shape and material) for the successful spray forming of free- standing parts is studied.
The as- sprayed parts were subjected to a post- heat- treatment and hot isostatic pressing. Subsequently, they were metallographically
inspected. The mechanical properties, such as hardness, Young’s moduli, and the fracture behavior during four-point bending,
are also examined. 相似文献
2.
热喷涂技术替代电镀硬铬的研究进展 总被引:17,自引:0,他引:17
周克崧 《中国有色金属学报》2004,14(Z1):182-191
从热喷涂技术的发展,高速火焰喷涂(HVOF)涂层的性能,包括耐磨性、耐蚀性、对基体耐疲劳性的影响,热喷涂涂层替代电镀硬铬镀层的成本以及应用4个方面综述了近年来热喷涂技术替代电镀硬铬的研究进展.指出热喷涂技术已经在航空、冶金、包装印刷和造纸等工业领域部分替代了电镀硬铬工艺;由于热喷涂技术对于大工件、厚涂层在性能和价格上的优势,热喷涂技术在其他工业领域的应用也将得到迅速发展. 相似文献
3.
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
4.
The principal aim of this study was to compare the sliding wear performance of as-sprayed and Hot Isostatically Pressed (HIPed)
thermal spray cermet (WC-12Co) coatings. Results indicate that HIPing technique can be successfully applied to post-treat
thermal spray cermet coatings for improved sliding wear performance, not only in terms of coating wear, but also in terms
of the total volume loss for test couples. WC-12Co coatings sprayed by a HVOF system were deposited on SUJ-2 bearing steel
substrate and then encapsulated and HIPed at 850 °C for one hour. A high frequency reciprocating ball on plate rig was used
to measure the sliding wear resistance of these coatings in dry conditions under steel and ceramic contact configurations
at two different loads. Results are discussed in terms of coating microstructure, microhardness, fracture toughness and residual
stress evaluations. Microstructural investigations indicate fundamental changes in grain morphology, whereas x-ray diffraction
revealed beneficial transformations in phase composition of these coatings during the HIPing post treatment. The effects of
these microstructural changes on the physical properties and wear resistance are discussed. 相似文献
5.
J. Porcayo-Calderon J. G. Gonzalez-Rodriguez L. Martinez 《Journal of Materials Engineering and Performance》1998,7(1):79-87
A Fe75Si thermal spray coating was applied on the surface of a plain carbon steel baffle plate. Beneath this coating, a Ni20Cr
coating was applied to give better adherence to the silicon coating. The baffle was installed in the high-temperature, fireside,
corrosion zone of a steam generator. At the same time, an uncoated 304 stainless steel baffle was installed nearby for comparison.
For 13 months the boiler burned heavy fuel oil with high contents of vanadium. The samples were studied employing scanning
electron microscopy, x-ray microanalysis, and x-ray diffraction techniques. After that, it was possible to inspect the structural
state of the components, and it was found that the stainless steel baffle plates were destroyed almost completely by corrosion,
whereas the carbon steel coated baffle plate did not suffer a significant attack, showing that the performance of the thermal
spray coating was outstanding and that the coating was not attacked by vanadium salts of the molten slag. 相似文献
6.
Technical and Economical Aspects of Current Thermal Barrier Coating Systems for Gas Turbine Engines by Thermal Spray and EBPVD: A Review 总被引:3,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
7.
飞机辅助动力装置(Auxiliary Power Unit,APU)是当前主流民用飞机上必不可少的部件,而热障涂层在APU中的应用能够减少发动机油耗、提升效率、延长热端部件的使用寿命。首先概述了飞机辅助动力装置的结构和工作原理,以及热障涂层的材料及结构体系。其次归纳了飞机APU常见热端部件中热障涂层的制备技术及应用特点,主要对大气等离子(AirPlasmaSpraying,APS)和电子束物理气相沉积(Electron–Beam Physical Vapor Deposition,EB–PVD)等2种热障涂层进行了论述。在此基础上,重点综述了热障涂层在民用飞机APU中的典型失效形式,包括高温氧化失效、烧结失效、CMAS腐蚀、颗粒物冲击等,同时结合热障涂层热生长氧化物(Thermally Grown Oxide,TGO)生长、应变能释放、蠕变与疲劳、颗粒物沉积、外来物损伤等行为,对以上失效形式的失效机理进行了重点论述;分别从微观结构观察、断裂力学参数计算、有限元建模等方面详细阐述了飞机APU热障涂层的失效分析手段与方法。最后结合航空公司的实际运营情况对提升APU使用寿命和系统可靠性给出了... 相似文献
9.
10.
W. P. Parks E. E. Hoffman W. Y. Lee I. G. Wright 《Journal of Thermal Spray Technology》1997,6(2):187-192
The Department of Energy’s Advanced Turbine Systems (ATS) program is aimed at fostering the devel-opment of a new generation
of land-based gas turbine systems with overall efficiencies significantly be-yond those of current state-of-the-art machines,
as well as greatly increased times between inspection and refurbishment, improved environmental impact, and decreased cost.
The proposed duty cycle of ATS ma-chines will emphasize different criteria in the selection of materials for the critical
components. In par-ticular, thermal barrier coatings (TBCs) will be an essential feature of the hot gas path components in
these machines. The goals of the ATS will require significant improvements in TBC technology, since these turbines will be
totally reliant on TBCs, which will be required to function on critical components such as the first-stage vanes and blades
for times considerably longer than those experienced in current applications. Important issues include the mechanical and
chemical stability of the ceramic layer and the metallic bond coat, the thermal expansion characteristics and compliance of
the ceramic layer, and the thermal conductivity across the thickness of the ceramic layer. 相似文献
11.
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
12.
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14.
A series of Ni alloys containing 36.15–44.54 wt.% Cr and 2.0–13.50 wt.% Al was synthesized by Self-Propagating High-Temperature
Synthesis (SHS) using a mixture of NiO, Cr2O3 and Al powders in order to obtain low-cost starting materials for thermal spray powder production. The experiments were carried
out with the addition of an excess stoichiometric amount of Al between 0 % and 30 %. Additions of CaO and CaF2 were also done to remove sulfur from the alloy and to investigate the effect on metal recovery. Thermochemical simulations
of the SHS processes were examined with the FactSage program. The products were characterized by chemical analysis, X-ray
diffraction (XRD), electron probe microanalysis (EPMA) and microhardness techniques. 相似文献
15.
采用4043,5356,7055三种焊接材料对喷射成形7475铝合金TIG焊接头的热裂纹敏感性进行了研究,对接头的力学性能进行了测试,分析了接头的微观组织及裂纹的形貌、相组成.结果表明,采用5356焊丝时热输入对焊接热裂纹敏感性影响较大,高热输入时母材中的铜和锌向焊缝进行扩散和焊缝中的镁在熔合区形成α-Al,Al0.403Zn0.597和Al7 Cu3 Mg6相的低熔共晶组织,并在晶界和枝晶间形成偏析,在焊接应力的作用下在熔合区内产生了贯穿性热裂纹;低热输入时接头没有出现热裂纹,但强度只有184 MPa;而4043和7055两种焊丝的热裂纹敏感性较小. 相似文献
16.
应用LS-DYNA大应变有限元耦合算法,研究了低温超音速火焰喷涂Fe粒子参数对喷涂层构建的影响.结果表明,随着粒子温度或者速度的升高,粒子所含内能的增加,使得涂层界面温度不断升高,粒子的沉积塑性应变发生变化.粒子在不同基体上的沉积特征表明基体硬度将影响沉积粒子与基体界面的结合状态.随着涂层的构成,后续粒子对已沉积粒子的高速撞击使得先沉积的粒子产生二次塑性变形,并引发温变.先沉积的粒子塑性变形引起的粗化作用将降低后续粒子沉积的临界速度.这些将导致涂层在拉应力作用下发生脆性断裂. 相似文献
17.
M. Pasandideh-Fard V. Pershin S. Chandra J. Mostaghimi 《Journal of Thermal Spray Technology》2002,11(2):206-217
We studied the deposition of nickel particles in a plasma spray on a stainless steel surface using both experiments and numerical
simulations. We developed a three-dimensional computational model of free-surface fluid flow that includes heat transfer and
solidification and used it to simulate the impact of nickel partcles. In our experiments, particles landing on a polished
stainless steel surface at a temperature below 300 °C splashed and formed irregular splats, whereas those deposited on substrates
heated above 400 °C formed round disk splats. Simulations showed that formation of fingers around the periphery of a spreading
drop is caused by the presence of a solid layer. Droplets that spread completely before the onset of solidification will not
splash. To sufficiently delay the instant at which solidification started in our simulations to obtain disk splats, we had
to increase the thermal contact resistance between the droplet and the substrate by an order of magnitude. We measured the
thickness of the oxide layer on the test surfaces used in our experiments and confirmed that heating them creates an oxide
layer on the surface that increases the thermal contact resistance. We demonstrated that the numerical model could be used
to simulate the deposition of multiple droplets on a surface to build up a coating. 相似文献
18.
A set of yttria partially stabilized zirconia coatings with different thickness was deposited on flat nickel-base alloy coupons
by air plasma spray (APS) under uncontrolled temperature conditions. In this way, the length of the spraying process (and
consequently the coating thickness) had a direct effect on phase composition as well as on the thermal properties of the material.
In particular, both the monoclinic phase percentage and thermal diffusivity increased considerably with the thickness. Because
this trend was observed together with a slight but clearly visible increase in the total porosity, the interpretation of the
results was not straightforward, but required a detailed discussion of the thermal transport mechanism. Considering the complex
microstructure typical of APS coatings and the relevant role of porosity, it was shown how a modest reduction in the fraction
of closed pores can account for the observed increase in diffusivity. It was then proposed that the volume change associated
with the progressive tetragonal to monoclinic phase transformation can be responsible for the reduction of the closed porosity
of lenticular shape oriented parallel to the surface, in spite of the observed increase in the total porosity. 相似文献
19.
The process parameters of atmospheric plasma spraying (APS) influence the coating formation and properties of partially yttria
stabilized zirconia (PYSZ) thermal barrier coatings (TBC). Simulations can be used to investigate this dependency and to design
the coating process for a targeted production of TBCs. A whole process simulation was realized by modeling the linked subprocesses:
plasma torch, plasma free jet, powder particles characteristics, and coating formation. The coating formation can be described
by model approaches with different physical assumptions and geometric scales. One approach is the simulation of single powder
particles hitting the substrate surface. An alternative macroscale finite element model (FEM) model approach is applied in
the coating formation simulation. A group of particles is pooled in a splash that is dependent on the precalculated particle
distribution in front of the substrate. A third modeling approach is applied to calculate effective mechanical and thermodynamical
properties of coatings dependent on the experimentally obtained or calculated microstructure of the PYSZ TBC, which is based
on different homogenization methods. The application of three simulation approaches in the whole process simulation of APS
is discussed; advantages and disadvantages are elucidated. Results based on simulation and experiments are presented for a
variation of process parameters. Missing links in the multiscale approach are detected to make suggestions for future modeling
and simulation work.
This article was originally published inBuilding on 100 Years of Success, Proceedings of the 2006 International Thermal Spray Conference (Seattle, WA), May 15–18, 2006, B.R. Marple, M.M. Hyland, Y.-Ch. Lau, R.S. Lima, and J. Voyer, Ed., ASM International, Materials
Park, OH, 2006. 相似文献
20.
Ashok Kumar J. Boy Ray Zatorski L. D. Stephenson 《Journal of Thermal Spray Technology》2005,14(2):177-182
The cavitation and erosion resistance of 21 thermal spray coatings and four weld repair materials were investigated in the laboratory using cavitation jet and slurry erosion testing. Of the thermal spray coatings, Stellite® 6 deposited by the high velocity oxyfuel (HVOF) process had the lowest cavitation rate (11.7 mg/h). This was higher than the corresponding cavitation rate (3.2 mg/h) of 308 stainless steel weld metal currently used as a reference. In the slurry erosion testing, the volume loss of Stellite® 6 applied by the HVOF process was 5.33 cubic mm/h, much lower than the corresponding loss (11.17 cubic mm/h) in the currently used stainless steel 304 reference. Furthermore, the electrochemical potential difference between the carbon steel and HVOF sprayed Stellite 6 coating was 0.25 volts, half the potential difference between the 304 stainless steel carbon steel substrate, and will result in reduced galvanic corrosion of the substrate near the contact areas. Stellite 6 deposited by the HVOF process was recommended for repair of damage resulting from erosion and subsequent cavitation by caused by surface roughening. 相似文献