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1.
W. Wong P. Vo E. Irissou A. N. Ryabinin J.-G. Legoux S. Yue 《Journal of Thermal Spray Technology》2013,22(7):1140-1153
The effects of commercially pure titanium particle morphology (spherical, sponge, and irregular) and size distributions (mean particle sizes of 20-49 μm) on the cold spray process and resulting coating properties were investigated. Numerous powder and coating characterizations were performed including: powder oxygen and nitrogen contents, powder flowability, powder compressibility, coating microhardness, coating porosity, LOM/SEM analyses, and XRD. Compared to spherical powders, the sponge and irregular CP-Ti powders had higher oxygen content, poorer powder flowability, higher compression ratio, lower powder packing factor, and higher average particle impact velocities. XRD results showed no new phases present when comparing the various feedstock powders to corresponding coatings. A higher particle temperature was also obtained with larger particle size for all feedstock powder morphologies processed with the same set of spray parameters. A spherical powder with 29 μm mean particle size was found to have the lowest porosity coating and best cold sprayability. The relationships of several as-cold sprayed coating characteristics to the ratio of particle impact and critical velocities were also discussed. 相似文献
2.
X. K. Suo X. P. Guo W. Y. Li M. P. Planche H. L. Liao 《Journal of Thermal Spray Technology》2012,21(5):831-837
Two types of magnesium powders with different particle size distributions were deposited by cold spraying at different main gas temperatures. The effects of gas temperature and particle size distribution on the deposition efficiency of particles were studied. The microstructure of coatings was observed, and the porosity of coatings was evaluated. The deposition efficiency of particles increased, and the porosity of coatings decreased with the increase of gas temperature. The deposition efficiency of particles increased when using the powder with a smaller particle size distribution. Stainless steel and aluminum plates were used as substrates. The bonding strength and mechanism between the coating and substrate were studied. The commercial finite element software ABAQUS was used to help us better understand the deformation behavior of particles and substrates. The mean bonding strength slightly increased when aluminum plates were used as substrates. The bonding mechanism of Mg coatings on stainless steel and aluminum substrates was discussed. 相似文献
3.
Influence of Helium and Nitrogen Gases on the Properties of Cold Gas Dynamic Sprayed Pure Titanium Coatings 总被引:2,自引:0,他引:2
Wilson Wong Eric Irissou Anatoly N. Ryabinin Jean-Gabriel Legoux Stephen Yue 《Journal of Thermal Spray Technology》2011,20(1-2):213-226
This study investigates the effect of propellant gas, helium, and nitrogen during cold spraying of titanium coatings. Coatings were characterized by SEM and were evaluated for their deposition efficiency (DE), microhardness, and porosity. In selected conditions, three particle velocities were investigated in which for each condition, the propelling gases?? temperature and pressure were attuned to attain similar particle velocities for each gas. Observations show that loosely bonded particles can be detached by high-pressure supersonic gas stream. Selected coatings were characterized by XPS to analyze the occurrence of oxidation and nitridation. Although generally accepted that coating characteristics can be affected by particle temperature, results show that for the same particle velocity, DE and coating density are also a function of substrate temperature. In addition, a thick and fully dense cold sprayed titanium coating was achieved with optimized spray parameters and nozzle using helium. The corresponding average particle velocity was 1173 m/s. 相似文献
4.
Venkata Naga Vamsi Munagala Valary Akinyi Phuong Vo Richard R. Chromik 《Journal of Thermal Spray Technology》2018,27(5):827-842
The powder microstructure and morphology has significant influence on the cold sprayability of Ti6Al4V coatings. Here, we compare the cold sprayability and properties of coatings obtained from Ti6Al4V powders of spherical morphology (SM) manufactured using plasma gas atomization and irregular morphology (IM) manufactured using the Armstrong process. Coatings deposited using IM powders had negligible porosity and better properties compared to coatings deposited using SM powders due to higher particle impact velocities, porous surface morphology and more deformable microstructure. To evaluate the cohesive strength, multi-scale indentation was performed and hardness loss parameter was calculated. Coatings deposited using SM powders exhibited poor cohesive strength compared to coatings deposited using IM powders. Images of the residual indents showed de-bonding and sliding of adjacent splats in the coatings deposited using SM powders irrespective of the load. Coatings deposited using IM powders showed no evidence of de-bonding at low loads. At high loads, splat de-bonding was observed resulting in hardness loss despite negligible porosity. Thus, while the powders from Armstrong process lead to a significant improvement in sprayability and coating properties, further optimization of powder and cold spray process will be required as well as consideration of post-annealing treatments to obtain acceptable cohesive strength. 相似文献
5.
The WC particle size and its influence on the deposition of Co-based cermets are examined. Micron and nanostructured powders with similar Co content were employed. Varying the WC particle size influenced significantly the deposition efficiency of the coating process. Micrometer-structured WC-Co feedstocks did not permit coating build up when processed under comparable or elevated thermal spray parameters used for the nanostructured WC-Co feedstocks. In addition, micrometer-structured WC-Co coatings exhibited a conjoint erosion and deposition effect on the surface. Fine WC particles (< 1 μm) were observed near the substrate interface and larger WC particles (1-2 μm) in the vicinity of the coating surface. These observations indicate the existence of a critical WC particle size for deposition by the cold spray method and that the size criteria arises due to the formation and cohesion mechanisms within the coating layer.Nanostructured test specimens displayed (i) a dense microstructure with little presence of porosity, (ii) a crack free interface between the coating and substrate that indicated good adhesion, and (iii) no observable phase changes. The XRD patterns of each powder and their respective coatings did not have observable peak differences but the diffraction peak broadening of coatings indicated that there was grain refinement during the coating process. Furthermore, all nanostructured as-sprayed WC-Co coatings exhibited Vickers hardness values above HV1000. The nanostructured WC-Co coatings demonstrated adhesive strengths that exceeded the limits of the glue (60 MPa). 相似文献
6.
Effect of processing conditions on porosity formation in cold gas dynamic spraying of copper 总被引:1,自引:0,他引:1
Saden H. Zahiri Darren Fraser Stefan Gulizia Mahnaz Jahedi 《Journal of Thermal Spray Technology》2006,15(3):422-430
The cold gas dynamics process is a promising low-temperature spray process in which particles are accelerated in a supersonic
flow before impacting with substrate to be coated. In this study the effect of spray temperature, spray pressure, and particle
size on porosity formation in cold spray coatings are investigated. Results show that an increase in spray temperature and
a decrease in particle size lead to a decline in volume fraction of porosity. Furthermore, particle velocity and particle
temperature are determined to be the significant parameters for elimination of porosity. A model is proposed for estimation
of the volume fraction of porosity for alloy of this study. 相似文献
7.
Pei-Hu Gao Yi-Gong Li Chang-Jiu Li Guan-Jun Yang Cheng-Xin Li 《Journal of Thermal Spray Technology》2008,17(5-6):742-749
The limited deformation of hard cermet particles and impacted coating makes it difficult for conventional thermal spray powders to continuously build up on impact in cold spraying. In this study, three nanostructured WC-12Co powders with different porous structure and apparent hardness were employed to deposit WC-Co coatings on stainless steel substrate by cold spraying. The deposition characteristics of three powders of porosity from 44 to 5% were investigated. It was found that WC-Co coating is easily built-up using porous powders with WC particles bonded loosely and a low hardness. The microhardness of WC-12Co coatings varied from 400 to 1790 Hv with powders and spray conditions, which depends on the densification effects by impacting particles. With porous WC-Co powders, the fracture of particles on impact may occur and low deposition efficiency during cold spraying. The successful building up of coating at high deposition efficiency depends on the design of powder porous structure. 相似文献
8.
This paper presents what is our actual knowledge about sensors, used in the harsh environment of spray booths, to improve
the reproducibility and reliability of coatings sprayed with hot or cold gases. First are described, with their limitations
and precisions, the different sensors following the in-flight hot particle parameters (trajectories, temperatures, velocities,
sizes, and shapes). A few comments are also made about techniques, still under developments in laboratories, to improve our
understanding of coating formation such as plasma jet temperature measurements in non-symmetrical conditions, hot gases heat
flux, particles flattening and splats formation, particles evaporation. Then are described the illumination techniques by
laser flash of either cold particles (those injected in hot gases, or in cold spray gun) or liquid injected into hot gases
(suspensions or solutions). The possibilities they open to determine the flux and velocities of cold particles or visualize
liquid penetration in the core of hot gases are discussed. Afterwards are presented sensors to follow, when spraying hot particles,
substrate and coating temperature evolution, and the stress development within coatings during the spray process as well as
the coating thickness. The different uses of these sensors are then described with successively: (i) Measurements limited
to particle trajectories, velocities, temperatures, and sizes in different spray conditions: plasma (including transient conditions
due to arc root fluctuations in d.c. plasma jets), HVOF, wire arc, cold spray. Afterwards are discussed how such sensor data
can be used to achieve a better understanding of the different spray processes, compare experiments to calculations and improve
the reproducibility and reliability of the spray conditions. (ii) Coatings monitoring through in-flight measurements coupled
with those devoted to coatings formation. This is achieved by either maintaining at their set point both in-flight and certain
spray parameters (spray pattern, coating temperature…), or defining a good working area through factorial design, or using
artificial intelligence based on artificial neural network (ANN) to predict particle in-flight characteristics and coating
structural attributes from the knowledge of processing parameters. 相似文献
9.
Particle melting behavior during high-velocity oxygen fuel (HVOF) thermal spraying was investigated using Inconel 625 powders.
The powder characteristics and coating properties were investigated using scanning electron microscopy (SEM), x-ray, and microhardness
studies. Results indicated that the volume fraction of unmelted particles in the coatings was dependent on the proportion
of powder within a specified size range, in these experiments, 30 to 50 μm. This particle size range was primarily determined
by the particle temperature, which was measured during spraying. Particle temperature significantly decreased as particle
size increased. The microhardness values for the coatings containing unmelted particles were predicted by a simple rule-of-mixtures
equation for the case of a low volume fraction of unmelted particles. However, for the condition of high volume fraction of
unmelted particles, the measured microhardness values did not compare favorably with the calculated values, probably due to
the presence of porosity, which occurred in the form of voids found among unmelted particles. The microstructure and characteristics
of the feedstock powder were retained in the corresponding coating under certain spray conditions. 相似文献
10.
F. D. Witherspoon D. W. Massey R. W. Kincaid G. C. Whichard T. A. Mozhi 《Journal of Thermal Spray Technology》2002,11(1):119-128
The quality and durability of coatings produced by many thermal spray techniques could be improved by increasing the velocity
with which coating particles impact the substrate. Additionally, better control of the chemical and thermal environment seen
by the particles during flight is crucial to the quality of the coating. A high velocity thermal spray device is under development
through a Ballistic Missile Defense Organization Small Business Innovation Research (SBIR) project, which provides significantly
higher impact velocity for accelerated particles than is currently available with existing thermal spray devices. This device
utilizes a pulsed plasma as the accelerative medium for powders introduced into the barrel. Recent experiments using a particle
imaging diagnostic system showed that the device can accelerate stainless steel and WC-Co powders to velocities ranging from
1500 to 2200 m/s. These high velocities are accomplished without the use of combustible gases and without the need of a vacuum
chamber, while maintaining an inert atmosphere for the particles during acceleration. The high velocities corresponded well
to modeling predictions, and these same models suggest that velocities as high as 3000 m/s or higher are possible. 相似文献
11.
Dowon Seo Kazuhiro Ogawa Tetsuo Shoji Shozo Murata 《Journal of Thermal Spray Technology》2007,16(5-6):954-966
The effect of particle size distribution on the degradation behavior of plasma sprayed CoNi- and CoCrAlY coatings during isothermal
oxidation was investigated, in terms of the oxygen content, porosity, surface roughness, and oxide scale formation. The results
show that the degradation of both coatings was considerably influenced by the starting particle size distribution. It also
shows that in the as-sprayed vacuum plasma spray (VPS) coatings the oxygen content on the coating surface increased significantly
with decreased average particle size. But after thermal exposure, the difference of the oxygen contents between the coatings
with different particle size was decreased. The powder with various particle size resulted in low porosity inside the coatings
during the deposition process. The surface roughness of the coatings increased with increased particle size. The small particles
produced a relatively smooth surface, and the oxide growth in the coating deposited by small particle was slower than that
in the large particle coating.
This article is an invited paper selected from presentations at the 2007 International Thermal Spray Conference and has been
expanded from the original presentation. It is simultaneously published in Global Coating Solutions, Proceedings of the 2007 International Thermal Spray Conference, Beijing, China, May 14-16, 2007, Basil R. Marple, Margaret M. Hyland, Yuk-Chiu Lau, Chang-Jiu Li, Rogerio S. Lima, and Ghislain
Montavon, Ed., ASM International, Materials Park, OH, 2007. 相似文献
12.
本文利用超音速火焰喷涂技术喷涂四种不同粒径的WC-17Co粉末,评价粉末粒径对涂层机械性能和抗磨粒磨损性能的影响。结果表明,粉末的粒径越小,在超音速焰流作用下获得的速度和温度越高,形成的涂层越致密,颗粒间的粘接强度越高,同时涂层的显微硬度也越高。WC-17Co粉末的粒径越小,获得涂层的孔隙直径越小,颗粒间的粘接缺陷越少,因此涂层的抗磨粒磨损性能越好。但是当WC-17Co粉末的粒径过于微小时,涂层的断裂韧性将受到影响。在本文研究的四种粒径分布的WC-17Co粉末中,中间粒径且分布范围集中的粉末制得的涂层兼具良好的机械性能和抗磨粒磨损性能。 相似文献
13.
《Surface & coatings technology》1987,31(1):1-10
The particle size distribution of the spray material is recognized as an important parameter in plasma spraying, although it is still a subject of controversy. However, it stands to reason that all the particles impinging on the substrate must be in a molten state. Overheating of small particles leads to vaporization and loss in efficiency. Inadequately heated coarse particles result also in reduced efficiency and in poor quality coatings.Titanium carbide is a material of considerable interest, mostly in the hard surfacing industry and for high thermal flux protection. For TiC coatings prepared by plasma spraying, attempts have been made to produce dense coatings. Previous studies on gaseous environments and spraying parameters always resulted in porous deposits. This study assesses the influence of the particle size distribution on deposition efficiency and coating density. Commercial TiC powders were classified in different fractions and sprayed under selected spraying conditions. The results indicate that both the size and particle size distribution of powders play a decisive role with respect to deposition efficiency and coating density. 相似文献
14.
冷喷涂由于具有粉末加热温度低、涂层中氧含量及孔隙率较常规热喷涂涂层显著降低等特点,而广泛应用于制备各种类型的涂层或块体材料。近年来,冷喷涂设备及工艺的改善使其在增材制造和零件修复方面也具有极大的应用前景。综述了冷喷涂制备高性能软质相金属和硬质相金属/非金属涂层的研究进展,重点围绕原始颗粒结构、冷喷涂工艺参数、添加第二相和后处理手段对涂层制备及性能优化的效果进行总结,并对冷喷涂制备复合涂层的结合机理进行了阐述,包括软质相颗粒形成单一涂层和添加硬质相颗粒复合涂层的结合机理,且涂层中颗粒之间的结合主要为机械结合、物理结合、冶金结合和化学结合中的一种或多种结合形式。同时,介绍了冷喷涂技术在增材制造领域和零件修复方面的研究进展和存在的问题。最后,分析总结了冷喷涂的应用前景和存在的问题。 相似文献
15.
Tantalum (Ta) coatings have been produced using a relatively new process, kinetic spray. Ta starting powders having particle
diameters greater than 65 μm are injected into a de Laval-type nozzle, entrained in a supersonic gas stream, and accelerated
to high velocities due to drag effects. The particles’ kinetic energy is transformed via plastic deformation into strain and
heat on impact with the substrate surface. Particles are not thermally softened or melted, producing relatively low oxide,
reduced residual stress, high adhesion and low porosity coatings. Analysis of the mechanical and physical properties of these
Ta coatings demonstrated increasing hardness, cohesive adhesion, and decreasing porosity as a function of particle velocity.
Comparison between kinetically sprayed coatings and coatings produced using conventional coating methods will be discussed. 相似文献
16.
MCrAlY bondcoats (M = Co, Ni) are used to protect metallic substrates from oxidation and to improve adhesion of ceramic thermal barrier coatings for high temperature applications, such as in land-based and aviation turbines. Since MCrAlYs are prone to take up oxygen during thermal spraying, bondcoats often are manufactured under inert gas conditions at low pressure. Plasma spraying at atmospheric conditions is a cost-effective alternative if it would be possible to limit the oxygen uptake as well as to obtain sufficiently dense microstructures. In the present work, high-velocity spray parameters were developed for the TriplexPro 210 three-cathode plasma torch using MCrAlY powders of different particle size fractions to achieve these objectives. The aims are conflictive since the former requires cold conditions, whereas the latter is obtained by more elevated particle temperatures. High particle velocities can solve this divergence as they imply shorter time for oxidation during flight and contribute to coating densification by kinetic rather than thermal energy. Further aims of the experimental work were high deposition efficiencies as well as sufficient surface roughness. The oxidation behavior of the sprayed coatings was characterized by thermal gravimetric analyses and isothermal heat treatments. 相似文献
17.
Taeyoung Han Zhibo Zhao Bryan A. Gillispie John R. Smith 《Journal of Thermal Spray Technology》2005,14(3):373-383
The kinetic spray coating process involves impingement of a substrate by particles of various material types at high velocities.
In the process, particles are injected into a supersonic gas stream and accelerated to high velocities. A coating forms when
the particles become plastically deformed and bond to the substrate and to one another upon collision with the substrate.
Coating formation by the kinetic spray process can be affected by a number of process parameters. In the current study, several
spray variables were investigated through computational modeling and experiments. The examined variables include the temperature
and pressure of the primary gas, the cross-sectional area of the nozzle throat, the nozzle standoff distance from a substrate,
and the surface condition of nozzle interior and the powder gas flow. Experimental verification on the effects of these variables
was performed primarily using relatively large-size aluminum particles (63–90 μm) as the feedstock material. It was observed
that the coating formation is largely controlled by two fundamental variables of the sprayed particles: particle velocity
and particle temperature. The effects of different spray conditions on coating formation by the kinetic spray process can
be generally interpreted through their influences on particle velocity and/or particle temperature. Though it is limited to
accelerate large particles to high velocities using compressed air or nitrogen as carrier gas, increasing particle temperature
provides an additional means that can effectively enhance coating formation by the kinetic spray process. 相似文献
18.
Cold spraying enables a variety of metals dense coatings onto metal surfaces. Supersonic gas jet accelerates particles which undergo with the substrate plastic deformation. Different bonding mechanisms can be created depending on the materials. The particle–substrate contact time, contact temperature and contact area upon impact are the parameters influencing physicochemical and mechanical bonds. The resultant bonding arose from plastic deformation of the particle and substrate and temperature increasing at the interface. The objective was to create specific topography to enable metallic particle adhesion onto ceramic substrates. Ceramic did not demonstrate deformation during the impact which minimized the intimate bonds. Laser surface texturing was hence used as prior surface treatment to create specific topography and to enable mechanical anchoring. Particle compressive states were necessary to build up coating. The coating deposition efficiency and adhesion strength were evaluated. Textured surface is required to obtain strong adhesion of metallic coatings onto ceramic substrates. Consequently, cold spray coating parameters depend on the target material and a methodology was established with particle parameters (diameters, velocities, temperatures) and particle/substrate properties to adapt the surface topography. Laser surface texturing is a promising tool to increase the cold spraying applications. 相似文献
19.
冷喷涂TC4涂层临界沉积速度计算及制备涂层性能研究 总被引:1,自引:1,他引:0
目的研究冷喷涂TC4涂层的临界沉积速度及粒子温度对临界沉积速度的影响规律,并研究气体压强对沉积涂层性能的影响规律。方法理论研究上,采用有限元LS-DYNA软件中的Johnson-Cook塑性模型,选取3D164计算单元建立模型,研究粒子在不同温度和不同速度下碰撞基体后的形貌特征,确定粒子沉积临界速度。试验研究上,采用N_2作为冷喷涂驱动气体,在TC4合金上制备TC4涂层,然后采用SEM、Image J图像分析软件、硬度计等分析已沉积涂层的孔隙率和硬度等性能。结果 25、400、500、600℃温度下,计算表明10μm的TC4合金粒子在TC4基板上的临界沉积速度分别为730、465、392、361 m/s,即随粒子温度升高,粒子临界沉积速度降低,粒子沉积成涂层更容易。采用冷喷涂工艺在TC4基板上沉积TC4涂层,在N_2温度600℃、气体压力3 MPa的条件下,制备的TC4涂层厚度约1000μm,与TC4钛合金基体结合紧密,涂层孔隙率约为6.46%。结论气体温度升高,粒子临界沉积速度降低;气体压强变大,制备的涂层厚度就大且更加致密。 相似文献
20.
P. Suresh Babu D. S. Rao G. V. N. Rao G. Sundararajan 《Journal of Thermal Spray Technology》2007,16(2):281-290
The detonation spraying is one of the most promising thermal spray variants for depositing wear and corrosion resistant coatings.
The ceramic (Al2O3), metallic (Ni-20 wt%Cr) , and cermets (WC-12 wt%Co) powders that are commercially available were separated into coarser
and finer size ranges with relatively narrow size distribution by employing centrifugal air classifier. The coatings were
deposited using detonation spray technique. The effect of particle size and its distribution on the coating properties were
examined. The surface roughness and porosity increased with increasing powder particle size for all the coatings consistently.
The feedstock size was also found to influence the phase composition of Al2O3 and WC-Co coatings; however does not influence the phase composition of Ni-Cr coatings. The associated phase change and %porosity
of the coatings imparted considerable variation in the coating hardness, fracture toughness, and wear properties. The fine
and narrow size range WC-Co coating exhibited superior wear resistance. The coarse and narrow size distribution Al2O3 coating exhibited better performance under abrasion and sliding wear modes however under erosion wear mode the as-received
Al2O3 coating exhibited better performance. In the case of metallic (Ni-Cr) coatings, the coatings deposited using coarser powder
exhibited marginally lower-wear rate under abrasion and sliding wear modes. However, under erosion wear mode, the coating
deposited using finer particle size exhibited considerably lower-wear rate. 相似文献