共查询到20条相似文献,搜索用时 31 毫秒
1.
O. Stier 《Journal of Thermal Spray Technology》2014,23(1-2):131-139
The cost structure of the cold spray (CS) process is analyzed using a generic cost model applicable to all present types of CS systems (“high pressure,” “low pressure,” KM?, “kinetic spraying,” etc.) and kinds of application (coating, restoration, additive manufacturing, near-net forming). The cost model has originally been developed at SIEMENS and is easy to use, while being sufficiently accurate to support decisions. The dependence of the process costs on the gas stagnation properties is discussed. It is shown (i) that high pressure is generally favorable, (ii) that He-N2 blends possess economic potential, and (iii) that He recovery saves costs in high volume production, even when He-N2 blends are used. The cost model allows for the determination of the cost-optimal He concentration of the propellant gas for a given application. CS is, among others, suited to spray bond coatings on gas turbine blades and offers cost-saving potential, as shown in a case study. 相似文献
2.
Effect of the increase in the entrance convergent section length of the gun nozzle on the high-velocity oxygen fuel and cold spray process 总被引:6,自引:1,他引:5
Nozzle geometry, which influences combustion gas dynamics and, therefore, sprayed particle behavior, is one of the most important
parameters in the high-velocity oxygen-fuel (HVOF) thermal spray process. The nozzle geometry is also important in the cold
spray method. The gas flows in the entrance convergent section of the nozzle exhibit a relatively higher temperature and are
subsonic; thus, this region is most suitable for heating spray particles.
In this study, numerical simulation and experiments investigated the effect of the entrance geometry of the gun nozzle on
the HVOF process. The process changes inside the nozzle, as obtained by numerical simulation studies, were related to the
coating properties. An Al2O3-40 mass% TiO2 powder was used for the experimental studies. The change in entrance convergent section length (rather than barrel part length
or total length) of the gun nozzle had a significant effect on the deposition efficiency, microstructure, and hardness. The
deposition efficiency and hardness increased as this geometry increased. On the other hand, the calculated and measured particle
velocity showed a slight decrease. This effect on the HVOF process will also be applied to the nozzle design for the cold
spray method. 相似文献
3.
Reactive thermal spray by high velocity ceramic jet and characterization of the coatings 总被引:13,自引:0,他引:13
A ceramic jet composed of molten particles in an electrothermally exploded powder spray was identified by the flash, soft
x-ray radiography technique. The velocity of the leading edge of the jet was estimated to be 900 m/s. The coating obtained
by a ceramic jet of titanium diboride consisted of a mixing layer of the substrate material and sprayed ceramics. A coating,
which exhibited no pores or cracks, was formed through the dense deposition and solidification of spray droplets. The successive
impacts of the droplets caused melting and stirring of the substrate surface to form a mixing layer. Some of these layers
were formed due to capillary movement of the molten substrate material into the fractures of coarse ceramic particles. Thermal
spray by chemical reaction between titanium and boron nitride particles resulted in a composite coating of TiN and TiB2. The character of the mixing layer indicated that the depth profiles depended on the substrate material. 相似文献
4.
Qiang Wang Kevin Spencer Nick Birbilis Ming-Xing Zhang 《Surface & coatings technology》2010,205(1):50-4671
Al-Al2O3 composite coatings were produced on AZ91D magnesium alloy substrates using kinetic metallization (KM), which is a special type of cold spray using a convergent barrel nozzle to attain sonic velocity. The effect of the volume fraction of Al2O3 particles and KM spray temperatures on the microstructure, hardness of the composite coatings, the deposition efficiency, and the bond strength between the coating and substrate was studied. Results show that addition of Al2O3 particles not only significantly improves the density of the coating, but also enhances the deposition efficiency to an optimum value. The bond strength of the composite coatings with the substrate was found to be much stronger than the coating itself, measured using a specially designed lug shear method. Furthermore, based on bond strength data and SEM analysis, higher Al2O3 content resulted in a failure mode transition from adhesive failure to cohesive failure. This is considered a result of a competition between the strengthening of the ceramic reinforcing particles at the coating/substrate interface, and the weakening of coating cohesive strength due to an increase in the proportion of weaker Al-Al2O3 bonds compared with stronger Al-Al bonds. Characterisation of the composite coating in terms of hardness, porosity and microstructure was also conducted. 相似文献
5.
Šárka Houdková Michaela Kašparová František Zahálka 《Journal of Thermal Spray Technology》2010,19(5):893-901
The spraying angle is one of the deposition parameters that influence the quality of thermally sprayed coatings. In theory,
decreasing the spraying angle results in lower process deposition efficiency, whereas the porosity of coatings increases,
becoming a cause of poorer microstructure and mechanical properties. In this study, the dependence of microstructure together
with the basic mechanical properties and wear of WC-Co and Cr3C2-NiCr high-velocity oxyfuel (HVOF) sprayed coatings on the spraying angle was investigated. For each coating, the maximum
spraying angle was determined that can be used without significantly decreasing coating quality. Based on the changes in properties
of coatings and requirements for the process deposition efficiency, a maximum 30° diversion from the normal spray direction
is recommended for WC-Co and 15° diversion for Cr3C2-NiCr coatings. 相似文献
6.
Cold Spraying of TiO<Subscript>2</Subscript> Photocatalyst Coating With Nitrogen Process Gas 总被引:1,自引:0,他引:1
Motohiro Yamada Hiroaki Isago Hiromi Nakano Masahiro Fukumoto 《Journal of Thermal Spray Technology》2010,19(6):1218-1223
Titanium dioxide (TiO2) is a promising material for photocatalyst coatings. However, it is difficult to fabricate a TiO2 coating with anatase phase by conventional thermal spray processes due to a thermal transformation to rutile phase. In this
paper, anatase TiO2 coatings were fabricated by the cold spray process. To understand the influence of process gas conditions on the fabrication
of the coatings, the gas nature (helium or nitrogen) and the gas temperature are investigated. It was possible to fabricate
TiO2 coatings with an anatase phase in all spraying conditions. The process gas used is not an important factor to fabricate TiO2 coatings. The thickness of the coatings increased with the process gas temperature increasing. It indicates that the deposition
efficiency of the sprayed particles can be enhanced by controlling the spray conditions. The photocatalytic activity of the
coatings is similar or better than the feedstock powder due to the formation of a large reaction area. Concludingly, cold
spraying is an ideal process for the fabrication of a TiO2 photocatalyst coating. 相似文献
7.
B. Robinson A. Tabecki S. Paul G. Shi A. Mills I. P. Parkin J. A. Darr H. L. de Villiers Lovelock 《Journal of Thermal Spray Technology》2017,26(1-2):161-172
The photocatalytic capabilities of titanium dioxide are widely published. Reported applications of titania coatings include air purification, water purification and self-cleaning. Suspension spray has been highlighted as a possible route for the deposition of highly active nanostructured TiO2 coatings. Published work has demonstrated the capabilities of suspension plasma spray and high-velocity suspension flame spray; however, little work exists for suspension flame spray (SFS). Herein, these three suspension spray processes are compared as regards their capability to produce photocatalytic TiO2 coatings and their potential for industrial scale-up. A range of coatings were produced using each process, manipulating coating parameters in order to vary phase composition and other coating characteristics to modify the activity. The coatings produced varied significantly between the processes with SFS being the most effective technique as regards future scale-up and coating photoactivity. SFS coatings were found to be up to nine times more active than analogous coating produced by CVD. 相似文献
8.
Compared to argon, plasmas generated by molecular gases and operated at the same electric current level contain much higher enthalpy. This is because molecular gases must dissociate before ionization, which requires larger energy input. The authors have developed a new DC plasma torch, which operates with a mixture of carbon dioxide (CO2) and methane (CH4). The torch was employed for plasma spray coating with input power in a range of 30 to 45 kW. This paper reports on the effect of CO2/CH4 mixtures on the particle conditions during spraying of nickel alloy powders. Results of gas composition analysis at various distances from the nozzle exit are presented. The particle in-flight conditions, coating microstructure, and deposition efficiency are analyzed. 相似文献
9.
M. Gindrat H.-M. H?hle K. von Niessen Ph. Guittienne D. Grange Ch. Hollenstein 《Journal of Thermal Spray Technology》2011,20(4):882-887
New dedicated coating processes which are based on the well-known LPPS™ technology but operating at lower work pressure (100 Pa)
are being actively developed. These hybrid technologies contribute to improve the efficiencies in the turbine industry such
as aero-engines and land-based gas turbines. They also have a great potential in the domain of new energy concepts in applications
like Solid Oxide Fuel Cells, membranes, and photovoltaic with the adoption of new ways of producing coatings by thermal spray.
Such processes include Plasma Spray-Thin Film (PS-TF) which gives the possibility to coat thin and dense layers from splats
through a classical thermal spray approach but at high velocities (400-800 m/s) and enthalpy (8000-15000 kJ/kg). Plasma Spray-PVD
(PS-PVD) which allows producing thick columnar-structured Thermal Barrier Coatings (100-300 μm) from the vapor phase with
the employment of the high enthalpy gun and specific powder feedstock material. On the other hand, the Plasma Spray-CVD (PS-CVD)
process uses modified conventional thermal spray components operated below 100 Pa which allows producing CVD-like coatings
(<1-10 μm) at higher deposition rates using liquid or gaseous precursors as feedstock material. The advantages of such thermal
spray-enhanced CVD processes are the high ionization degree and high throughput for the deposition of thin layers. In this
article, we present an overview of the possibilities and limitations encountered while producing thin film coatings using
liquid and gaseous precursors with this new type of low pressure plasma spray equipment and point out the challenges faced
to obtain efficient injection and mixing of the precursors in the plasma jet. In particular, SiO
x
thin films from Hexamethyldisiloxane (HMDSO or C6H18OSi2) can be deposited on wafers at deposition rates of up to 35 nm/s at an efficiency of about 50%. The process was also used
for producing metal oxide coatings (Al2O3, ZnO, and SnO2) by evaporating different metals in combination with an oxygen gas flow. The effect of process parameters on the deposition
rate, coating build up, uniformity, and quality of the coatings are discussed. An overview of different potential applications
of this new technology will be also presented. 相似文献
10.
Florin-Iuliu Trifa Ghislain Montavon Christian Coddet 《Journal of Thermal Spray Technology》2007,16(1):128-139
This article aims at presenting an expert system to assist the design and the simulation of 2-D shapes of alumina-titania
(i.e., Al2O3-13 wt.% TiO2) Atmospherically Plasma Sprayed (APS) coatings. Indeed, the expert system derives from a spray deposition mathematic model
resulting from experiments. The varied processing parameters were the geometric and the kinematics parameters, mainly, such
as: the relative speed gun-substrate, the spray distance, the spray angle, the relative positioning powder injector-spray
gun trajectory, the number of passes and the powder feed rate. The variations of the geometry and some of the structural parameters
were analyzed relatively to the aforementioned varied parameters. Thus, a large set of spray pattern parameters was designed.
This set considers mostly the spray pattern geometry. All the relationships between the processing parameters and the spray
pattern parameters were hence grouped in a spray deposition model. The second step of this work consisted in optimizing the
robotic (i.e., spray gun) trajectory using a robotic code, which permits a realistic simulation of the spray gun speed and
its inertia. Using this simulation software, a trajectory file was built. In the third step of the work, an expert system
was developed by combining the spray deposition model with the trajectory. The tasks of the expert system are: (1) to assist
the user in designing the coatings by selecting the processing parameters and (2) to simulate the coating shapes by integrating
the gun trajectory.
相似文献
Ghislain MontavonEmail: |
11.
Thermally sprayed carbide-based coatings are nowadays extensively considered as an alternative to electrolytic hard chrome (EHC) coatings to reduce the environmental impact and the overall cost associated with EHC process. In this investigation, high-velocity oxy-fuel (HVOF) spray process was employed to prepare coatings using the traditional carbide powders namely the WC-10Co4Cr, the Cr3C2-25NiCr and a new type of mixed carbide powder WC-40Cr3C2-25NiCr. The Powder deposition rate, basic mechanical properties, abrasive wear, slurry erosion and corrosion resistance of the three coatings were then compared with the EHC coating. The results show that WC-10Co4Cr coating exhibited the highest hardness, abrasive wear and slurry erosion resistance followed by WC-40Cr3C2-25NiCr, EHC, and Cr3C2-25NiCr coating. The deposition efficiency of the powders as per hierarchy was found to be WC-40Cr3C2-25NiCr > WC-10Co4Cr > Cr3C2-25NiCr and all the HVOF sprayed coatings exhibited higher corrosion resistance than EHC coating. The highest powder deposition efficiency coupled with low density, acceptable tribo-corrosion performance, as well as low post processing cost makes the HVOF sprayed WC-40Cr3C2-25NiCr coating a potential candidate to replace the EHC coating. 相似文献
12.
W. Tillmann E. Vogli I. Baumann G. Kopp C. Weihs 《Journal of Thermal Spray Technology》2010,19(1-2):392-408
Thermal spraying of fine feedstock powders allow the deposition of cermet coatings with significantly improved characteristics and is currently of great interest in science and industry. However, due to the high surface to volume ratio and the low specific weight, fine particles are not only difficult to spray but also show a poor flowability in the feeding process. In order to process fine powders reliably and to preserve the fine structure of the feedstock material in the final coating morphology, the use of novel thermal spray equipment as well as a thorough selection and optimization of the process parameters are fundamentally required. In this study, HVOF spray experiments have been conducted to manufacture fine structured, wear-resistant cermet coatings using fine 75Cr3C2-25(Ni20Cr) powders (?8 + 2 μm). Statistical design of experiments (DOE) has been utilized to identify the most relevant process parameters with their linear, quadratic and interaction effects using Plackett-Burman, Fractional-Factorial and Central Composite designs to model the deposition efficiency of the process and the majorly important coating properties: roughness, hardness and porosity. The concept of desirability functions and the desirability index have been applied to combine these response variables in order to find a process parameter combination that yields either optimum results for all responses, or at least the best possible compromise. Verification experiments in the so found optimum obtained very satisfying or even excellent results. The coatings featured an average microhardness of 1004 HV 0.1, a roughness Ra = 1.9 μm and a porosity of 1.7%. In addition, a high deposition efficiency of 71% could be obtained. 相似文献
13.
Mohamed Elhoriny Martin Wenzelburger Andreas Killinger Rainer Gadow 《Journal of Thermal Spray Technology》2017,26(4):735-744
The coating buildup process of Al2O3/TiO2 ceramic powder deposited on stainless-steel substrate by atmospheric plasma spraying has been simulated by creating thermomechanical finite element models that utilize element death and birth techniques in ANSYS commercial software and self-developed codes. The simulation process starts with side-by-side deposition of coarse subparts of the ceramic layer until the entire coating is created. Simultaneously, the heat flow into the material, thermal deformation, and initial quenching stress are computed. The aim is to be able to predict—for the considered spray powder and substrate material—the development of residual stresses and to assess the risk of coating failure. The model allows the prediction of the heat flow, temperature profile, and residual stress development over time and position in the coating and substrate. The proposed models were successfully run and the results compared with actual residual stresses measured by the hole drilling method. 相似文献
14.
Seven different Al2O3-based suspensions were prepared by dispersing two nano-sized Al2O3 powders (having analogous size distribution and chemical composition but different surface chemistry), one micron-sized powder and their mixtures in a water + isopropanol solution. High velocity suspension flame sprayed (HVSFS) coatings were deposited using these suspensions as feedstock and adopting two different sets of spray parameters.The characteristics of the suspension, particularly its agglomeration behaviour, have a significant influence on the coating deposition mechanism and, hence, on its properties (microstructure, hardness, elastic modulus). Dense and very smooth (Ra ~ 1.3 μm) coatings, consisting of well-flattened lamellae having a homogeneous size distribution, are obtained when micron-sized (~ 1-2 μm) powders with low tendency to agglomeration are employed. Spray parameters favouring the break-up of the few agglomerates present in the suspension enhance the deposition efficiency (up to > 50%), as no particle or agglomerate larger than ~ 2.5 μm can be fully melted. Nano-sized powders, by contrast, generally form stronger agglomerates, which cannot be significantly disrupted by adjusting the spray parameters. If the chosen nanopowder forms small agglomerates (up to a few microns), the deposition efficiency is satisfactory and the coating porosity is limited, although the lamellae generally have a wider size distribution, so that roughness is somewhat higher. If the nanopowder forms large agglomerates (on account of its surface chemistry), poor deposition efficiencies and porous layers are obtained.Although suspensions containing the pure micron-sized powder produce the densest coatings, the highest deposition efficiency (~ 70%) is obtained by suitable mixtures of micron- and nano-sized powders, on account of synergistic effects. 相似文献
15.
为解决 YSZ(Y2O3 部分稳定的 ZrO2 ) 陶瓷基高温封严涂层沉积效率较低和易于过早剥落失效的问题,选择氧化铝 (Al 2O3 )、钇铝石榴石(Y3Al 5O12 ,YAG)及镁铝尖晶石(MgAl 2O4 )为三种高温黏结相,通过喷雾造粒的方法分别制备出 B0(无黏结相)、B1(含 Al 2O3 )、B2(含 YAG)和 B3(含 MgAl 2O4 )等四种 YSZ 基团聚颗粒,研究黏结相对涂层沉积效率和热循环性能的影响。 结果表明,YAG 的黏附和包裹作用最强,与 B0 型粉末相比,B2 型粉末的沉积效率提高了 181. 49%;热循环过程中不断增长的裂纹扩展驱动力和陶瓷材料的脆性属性是导致陶瓷涂层剥落失效的主要原因,由于 YAG 相的弥散增韧作用,B2 型涂层的断口呈现出类韧窝形貌,与 B0 型涂层相比,B2 型涂层的断裂韧性提高了 39. 76%,热循环寿命提高了 43. 68%。 YAG 黏结相的添加显著地提高了 YSZ 陶瓷基高温封严涂层的沉积效率,同时较好地提高了涂层的热循环寿命。 相似文献
16.
Influence of the Spray Angle on the Characteristics of Atmospheric Plasma Sprayed Hard Material Based Coatings 总被引:1,自引:0,他引:1
Wolfgang Tillmann Evelina Vogli Benjamin Krebs 《Journal of Thermal Spray Technology》2008,17(5-6):948-955
This paper presents an investigation of the influence of the spray angle on thermally sprayed coatings. Spray beads were manufactured with different spray angles between 90 and 20° by means of atmospheric plasma spraying (APS) on heat-treated mild steel (1.0503). WC-12Co and Cr3C2-10(Ni20Cr) powders were employed as feedstock materials. Every spray bead was characterized by a Gaussian fit. This opens the opportunity to analyze the influence of the spray angle on coating properties. Furthermore, metallographic studies of the surface roughness, porosity, hardness, and morphology were carried out and the deposition efficiency as well as the tensile strength was measured. The thermally sprayed coatings show a clear dependence on the spray angle. A decrease in spray angle changes the thickness, width, and form of the spray beads. The coatings become rougher and their quality decreases. 相似文献
17.
Vacuum kinetic spray (VKS), also called aerosol deposition method, is a spray process that makes it possible to fabricate dense ceramic films at room temperature. Although the deposition rate of VKS is better than conventional ceramic coating processes, the deposition properties are still poor for industrial use. In this respect, this work investigates the role of particle size on the deposition behavior by blending two alumina powders having different sizes. It results in suggestions for increasing the deposition efficiency and rate. The microstructure and mechanical properties of films revealed that nanosized particles directly took part in deposition and participated in increasing the deposition rate despite the low adhesion between crystallites. In contrast, relatively large submicron-sized particles mainly contributed to the coating consolidation via severe friction, which strengthened the fragment bonding. Submicron-sized particles also were indirectly deposited as crystallites after sufficient fragmentation. Therefore, it is suggested that the deposition behavior and film properties in VKS can be controlled by adjusting the mixing ratio of two alumina powders with different particle size ranges. 相似文献
18.
Maria Ophelia Jarligo Georg Mauer Martin Bram Stefan Baumann Robert Vaßen 《Journal of Thermal Spray Technology》2014,23(1-2):213-219
Plasma spray physical vapor deposition (PS-PVD) is a very promising route to manufacture ceramic coatings, combining the efficiency of thermal spray processes and characteristic features of thin PVD coatings. Recently, this technique has been investigated to effectively deposit dense thin films of perovskites particularly with the composition of La0.58Sr0.4Co0.2Fe0.8O3?δ (LSCF) for application in gas separation membranes. Furthermore, asymmetric type of membranes with porous metallic supports has also attracted research attention due to the advantage of good mechanical properties suitable for use at high temperatures and high permeation rates. In this work, both approaches are combined to manufacture oxygen transport membranes made of gastight LSCF thin film by PS-PVD on porous NiCoCrAlY metallic supports. The deposition of homogenous dense thin film is challenged by the tendency of LSCF to decompose during thermal spray processes, irregular surface profile of the porous metallic substrate and crack and pore-formation in typical ceramic thermal spray coatings. Microstructure formation and coating build-up during PS-PVD as well as the annealing behavior at different temperatures of LSCF thin films were investigated. Finally, measurements of leak rates and oxygen permeation rates at elevated temperatures show promising results for the optimized membranes. 相似文献
19.
NiCr/(Cr3C2-BaF2·CaF2) coating was fabricated by atmospheric plasma spray technology using clad powder. The coating shows low porosity, high microhardness and bonding strength, and it also exhibits good friction reduction and wear resistance at elevated temperatures up to 800 °C which is due to the formation of a kind of continuous BaF2·CaF2 eutectic lubricating film. The excellent mechanical and tribological properties of the coating are partially attributed to the protection of NiCr layer of the composite powders which can decrease oxidation, decarburization of Cr3C2, and ablation of BaF2·CaF2 eutectic during spray and deposition process. 相似文献
20.
Influence of the ceramic particle size on the process of formation of cermet coatings by cold spray is experimentally studied.
A specially developed nozzle with separate injection of ceramic and metal powders into the gas stream is used in the experiments.
The results obtained demonstrate that fine ceramic powders (Al2O3, SiC) produce a strong activation effect on the process of spraying soft metal (Al, Cu) and increase deposition efficiency
of the metal component of the mixture compared to the pure metal spraying. At the same time, coarse ceramic powder produces
a strong erosion effect that considerably reduces coating mass growth and deposition efficiency of the metal component. It
is experimentally shown that the addition of fine hard powder to soft metals as Al and Cu allows to significantly reduce the
“critical” temperature (the minimum gas stagnation temperature at which a nonzero particle deposition is observed) for spraying
these metals. 相似文献