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1.
Powders of titanium alloy (Ti-6Al-4V) and bioactive glass (45S5) were deposited by flame spraying to fabricate composite porous
coatings for potential use in bone fixation implants. Bioactive glass and titanium alloy powder were blended and deposited
in various weight fractions under two sets of spray conditions, which produced different levels of porosity. Coatings were
characterized with cross-sectional optical microscopy, x-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier
transform infrared spectroscopy (FTIR). Immersion testing in simulated body fluid (SBF) was conducted for 0, 1, 7, and 14 days.
Hydroxyapatite (HA) was found on the bioactive glass-alloy composite coatings after 7 days of immersion; no HA was observed
after 14 days on the pure titanium alloy control coating. The HA formation on the alloy-bioactive glass composite coating
suggests that the addition of bioactive glass to the blend may greatly increase the bioactivity of the coating through enhanced
surface mineralization. 相似文献
2.
Wolfgang Tillmann Frank Walther Weifeng Luo Matthias Haack Jens Nellesen Marina Knyazeva 《Journal of Thermal Spray Technology》2018,27(1-2):50-58
In order to guarantee their protective function, thermal spray coatings must be free from cracks, which expose the substrate surface to, e.g., corrosive media. Cracks in thermal spray coatings are usually formed because of tensile residual stresses. Most commonly, the crack occurrence is determined after the thermal spraying process by examination of metallographic cross sections of the coating. Recent efforts focus on in situ monitoring of crack formation by means of acoustic emission analysis. However, the acoustic signals related to crack propagation can be absorbed by the noise of the thermal spraying process. In this work, a high-frequency impulse measurement technique was applied to separate different acoustic sources by visualizing the characteristic signal of crack formation via quasi-real-time Fourier analysis. The investigations were carried out on a twin wire arc spraying process, utilizing FeCrBSi as a coating material. The impact of the process parameters on the acoustic emission spectrum was studied. Acoustic emission analysis enables to obtain global and integral information on the formed cracks. The coating morphology and coating defects were inspected using light microscopy on metallographic cross sections. Additionally, the resulting crack patterns were imaged in 3D by means of x-ray microtomography. 相似文献
3.
以沥青为前驱体制备TiC/FeCrNi反应火焰喷涂复合涂层 总被引:4,自引:0,他引:4
以钛铁粉、CrFe粉、羰基镍粉和碳的前驱体(石油沥青)为原料,通过前驱体碳化复合技术制备了Ti-Fe-Cr-Ni-C反应喷涂复合粉末,并通过普通火焰喷涂成功地合成与沉积了TiC/FeCrNi复合涂层.采用XRD和SEM对喷涂粉末和涂层的相组成和显微结构进行了分析,同时对涂层耐磨性能进行了对比研究.研究结果表明:采用前驱体碳化复合技术制备的Ti-Fe-Cr-Ni-C反应喷涂复合粉末粒度均匀、无有害相生成;所制备的TiC/FeCrNi复合涂层由不同含量TiC颗粒分布于金属基体内部而形成的复合强化片层叠加而成,TiC颗粒呈纳米级;基体由(Fe,Cr)和Cr0.19Fe0.7Ni0.11两相组成;相同条件下,所获TiC/FeCrNi复合涂层磨损体积大约是常规火焰喷涂Ni60涂层的1/8. 相似文献
4.
Eric H. Jordan Chen Jiang Jeffrey Roth Maurice Gell 《Journal of Thermal Spray Technology》2014,23(5):849-859
The primary function of thermal barrier coatings (TBCs) is to insulate the underlying metal from high temperature gases in gas turbine engines. As a consequence, low thermal conductivity and high durability are the primary properties of interest. In this work, the solution precursor plasma spray (SPPS) process was used to create layered porosity, called inter-pass boundaries, in yttria-stabilized zirconia (YSZ) TBCs. IPBs have been shown to be effective in reducing thermal conductivity. Optimization of the IPB microstructure by the SPPS process produced YSZ TBCs with a thermal conductivity of 0.6 W/mK, an approximately 50% reduction compared to standard air plasma sprayed (APS) coatings. In preliminary tests, SPPS YSZ with IPBs exhibited equal or greater furnace thermal cycles and erosion resistance compared to regular SPPS and commercially made APS YSZ TBCs. 相似文献
5.
The present study investigated the influence of grit blasting, feedstock powder, and thermal spraying technology on performance
near the surface on the substrate’s side. The experimental results show that both the grit-blasting process and thermal spraying
process harden the substrate, and microhardness on or near the surface was noticeably increased. Grit blasting created deformed
regions next to the surface of the substrate and interface between entrapped grits and substrate. Initial equiaxed grains
in the deformed regions were elongated and spirally oriented surrounding impact spots. There were no visible changes in microstructure
caused by thermal spraying, and the elongated grain regions remained in the coated substrate. Substrate hardening was attributed
to grit blasting and associated heating due to flame rather than powder particle impacting during thermal spraying, thus feedstock
powder and individual thermal spray technology had no influence on the hardening. 相似文献
6.
Joel Voyer 《Journal of Thermal Spray Technology》2013,22(5):699-709
The wire flame spray process was used to produce electrically conductive and flexible Al coatings onto diverse textile fabrics. The investigation studied the influence of the spraying parameters and fabric materials on the electrical conductivity of the metal-fabric composites. Furthermore, this study showed that the production of flexible Li-ion batteries having good electrical properties based on the use of such flame-sprayed aluminium cathode current collectors is viable. Results show that a coating quantity threshold of about 20 mg/cm2 exists to obtain a sufficient electrical surface conductivity for a commercial use of the produced metal-fabric composites. An excellent electrical surface conductivity of the composites (about 500 SA) could be achieved through an adequate optimization of the spraying parameters. This conductivity increase enabled a reduction of the coating quantity and thus the flexibility of the fabric materials is better conserved, rendering the use of such composites for flexible batteries even more interesting. This study showed that the production of electrically conductive and flexible metal-fabric composites having sufficient electrical conductivity for the manufacture of flexible Li ions batteries is possible. This new method of producing such batteries represents an alternative to other chemically based processes which are hazardous to the environment because of their chemical nature. 相似文献
7.
介绍了一种用于测量薄膜样品和高压样品比热的一种芯片式量热计,该器件由美国加州大学伯克利分校的Frances Hellman研究组于15年前最先开发研制并投入使用,但其应用在中国尚未见报道。希望此文能为国内相关领域的研究人员起到抛砖引玉的作用。 相似文献
8.
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
9.
Ebrahim Gozali Mahrukh Mahrukh Sai Gu Spyros Kamnis 《Journal of Thermal Spray Technology》2014,23(6):940-949
The liquid feedstock or suspension as a different mixture of liquid fuel ethanol and water is numerically studied in high-velocity suspension flame spray (HVSFS) process, and the results are compared for homogenous liquid feedstock of ethanol and water. The effects of mixture on droplet aerodynamic breakup, evaporation, combustion, and gas dynamics of HVSFS process are thoroughly investigated. The exact location where the particle heating is initiated (above the carrier liquid boiling point) can be controlled by increasing the water content in the mixture. In this way, the particle inflight time in the high-temperature gas regions can be adjusted avoiding adverse effects from surface chemical transformations. The mixture is modeled as a multicomponent droplet, and a convection/diffusion model, which takes into account the convective flow of evaporating material from droplet surface, is used to simulate the suspension evaporation. The model consists of several sub-models that include premixed combustion of propane-oxygen, non-premixed ethanol-oxygen combustion, modeling of multicomponent droplet breakup and evaporation, as well as heat and mass transfer between liquid droplets and gas phase. 相似文献
10.
The microstructure features of coatings produced by a plasma spray process are affected significantly by the process parameters
such as powder size, spray gun nozzle size, total plasma gas flow, ratio of H2 + N2 over total gas flow, and so on. This article presents a study of the effects of these parameters on the microstructure (porosity,
formation of crack, unmelted particle and oxide phase) of NiCrAlY coatings deposited by the Mettech Axial III™ System. A Taguchi
array is used to design the spraying process parameters. The results of the microstructure evaluation are used to generate
regression equations for the prediction of coating microstructure based on process parameters. The results predicted from
the regression equations are in good agreement with the experimental results according to a confidence level of 0.95. Among
the parameters examined, the powder size and the ratio of H2 + N2 over total gas flow rate are the most significant parameters affecting the occurrence of crack, porosity, unmelted particle
and oxide. Within the range of the designed process parameters, lower powder size and higher ratio of H2 + N2 over total gas flow rate lead to less cracks, pores, unmelted particles but more oxides. Nozzle size has marginal influence
on oxides which increase with nozzle size. Gas flow rate has no direct influence on any coating feature evaluated with the
range of variation. 相似文献
11.
B. Torres P. Rodrigo M. Campo A. Ureña J. Rams 《Journal of Thermal Spray Technology》2009,18(4):642-651
Aluminum matrix composites reinforced with more that 50 vol.% of SiC particles were fabricated using oxyacetylene thermal
spraying. The sprayed material consisted of mixtures of aluminum powder with 60-85 vol.% of SiC particles. To favor the processing
of the composite, in some cases, the SiC particles were coated with silica following a sol-gel route. This allowed obtaining
as-sprayed samples with thickness above 2 mm and with porosity values below 2%. Post-processing of the samples by hot pressing
allowed to reduce further the porosity of the composites and to enhance their microstructural homogeneity. The whole process
of spraying and hot pressing has been optimized and the role played by the different spraying parameters and by time length
and temperature of hot pressing has been also studied. 相似文献
12.
菲亚特系列C539变速箱的3种拨叉制造技术要求较高,其性能好坏直接影响变速箱的换档操作性能、可靠性及寿命.由于热喷涂处理可使工件具有较好的耐磨性和润滑性能,以及能提高工件的疲劳强度,而且工艺灵活、投资少、见效快,所以在产品设计中,要求对拨叉的工作面进行Cu-Al和Ni-Al热喷涂处理.目前拨叉喷涂是南亚变速箱厂的关键工序,已连续生产5年,技术不断完善,产品质量已相当可靠和稳定. 相似文献
13.
热喷涂基体表面前处理技术的研究进展 总被引:3,自引:1,他引:3
热喷涂涂层与基体机械咬合的结合机理决定了基体表面前处理是热喷涂涂层中非常重要的处理工艺。文中概述了当前广泛应用的喷砂处理的工艺特点,指出砂粒易在基体表面镶嵌和对基体造成损伤是喷砂工艺的主要缺点,讨论了喷砂对高温合金单晶材料和超高强钢疲劳性能的影响,研究了软质基体表面超音速火焰喷涂WC涂层的免喷砂工艺。同时介绍了近年来其他热喷涂基体表面前处理方面的研究热点,包括高压水射流处理技术、机械粗化技术以及激光表面前处理,并重点阐述了其基本原理、特点及应用情况。 相似文献
14.
针对氮气喷射沉积镁合金雾化过程中的快速散热阻燃行为,采用数学模型模拟了镁合金喷射沉积过程中雾化气体与液滴之间的传热情况.结果表明,雾化气体速度随着喷射距离的增加呈单调递减趋势;雾化液滴先加速飞行,在液滴和气体速度相等后开始减速,随着粒径增大,液滴的最大速度减小;传热系数先减小再增加,且随着液滴粒径减小而增大,其平均值均在l000W· m-2·K-1以上;液滴的温度持续降低;在雾化阶段,液滴与气体之间传热的最小速率远远大于反应放热的最大速率,避免了喷射沉积过程中热量的蓄积,从而保障了氮气喷射沉积制备镁合金过程的生产安全. 相似文献
15.
16.
Thermal Spray Using a High-Frequency Pulse Detonation Combustor Operated in the Liquid-Purge Mode 总被引:1,自引:0,他引:1
T. Endo R. Obayashi T. Tajiri K. Kimura Y. Morohashi T. Johzaki K. Matsuoka T. Hanafusa S. Mizunari 《Journal of Thermal Spray Technology》2016,25(3):494-508
Experiments on thermal spray by pulsed detonations at 150 Hz were conducted. Two types of pulse detonation combustors were used, one operated in the inert gas purge (GAP) mode and the other in the liquid-purge (LIP) mode. In both modes, all gases were supplied in the valveless mode. The GAP mode is free of moving components, although the explosive mixture is unavoidably diluted with the inert gas used for the purge of the hot burned gas. In the LIP mode, pure fuel-oxygen combustion can be realized, although a liquid-droplet injector must be actuated cyclically. The objective of this work was to demonstrate a higher spraying temperature in the LIP mode. First, the temperature of CoNiCrAlY particles heated by pulsed detonations was measured. As a result, the spraying temperature in the LIP mode was higher than that in the GAP mode by about 1000 K. Second, the temperature of yttria-stabilized zirconia (YSZ) particles, whose melting point was almost 2800 °C, heated by pulsed detonations in the LIP mode was measured. As a result, the YSZ particles were heated up to about 2500 °C. Finally, a thermal spray experiment using YSZ particles was conducted, and a coating with low porosity was successfully deposited. 相似文献
17.
We investigated the research publications on thermal spray in the period of 1985-2015 using the data from Web of Science, Scopus and SciVal®. Bibliometrics analysis was employed to elucidate the country and institution distribution in various thermal spray research areas and to characterize the trends of topic change and technology progress. Results show that China, USA, Japan, Germany, India and France were the top countries in thermal spray research, and Xi’an Jiaotong University, Universite de Technologie Belfort–Montbeliard, Shanghai Institute of Ceramics, ETH Zurich, National Research Council of Canada, University of Limoges were among the top institutions that had high scholarly research output during 2005-2015. The terms of the titles, keywords and abstracts of the publications were analyzed by the Latent Dirichlet Allocation model and visually mapped using the VOSviewer software to reveal the progress of thermal spray technology. It is found that thermal barrier coating was consistently the main research area in thermal spray, and high-velocity oxy-fuel spray and cold spray developed rapidly in the last 10 years. 相似文献
18.
Xiaolong Chen Hiroshi Honda Seiji Kuroda Hiroshi Araki Hideyuki Murakami Makoto Watanabe Yoshio Sakka 《Journal of Thermal Spray Technology》2016,25(8):1638-1649
Effects of the ceramic powder size used for suspension as well as several processing parameters in suspension plasma spraying of YSZ were investigated experimentally, aiming to fabricate highly segmented microstructures for thermal barrier coating (TBC) applications. Particle image velocimetry (PIV) was used to observe the atomization process and the velocity distribution of atomized droplets and ceramic particles travelling toward the substrates. The tested parameters included the secondary plasma gas (He versus H2), suspension injection flow rate, and substrate surface roughness. Results indicated that a plasma jet with a relatively higher content of He or H2 as the secondary plasma gas was critical to produce highly segmented YSZ TBCs with a crack density up to ~12 cracks/mm. The optimized suspension flow rate played an important role to realize coatings with a reduced porosity level and improved adhesion. An increased powder size and higher operation power level were beneficial for the formation of highly segmented coatings onto substrates with a wider range of surface roughness. 相似文献
19.
Y. G. Shan C. H. Shen L. B. Jia J. Mostaghimi 《Journal of Thermal Spray Technology》2014,23(1-2):14-20
The low-temperature oxygen-fuel (LTOF) spray is a modification of high velocity oxygen fuel spray. In this process, the high-temperature gas is accelerated to supersonic speed through a Laval nozzle followed by a straight barrel. By injecting room temperature gas into the mixing chamber, the temperature of the gas can be controlled in a range of about 1000-2500 K, so that some oxygen and temperature-sensitive materials, such as titanium and copper, can avoid oxidation or decomposition during the spraying process. The purpose of this paper is to establish a 2-D mathematical model to simulate the supersonic gas dynamics and particles behavior in LTOF process. The temperature and velocity of the flow fields, and the trajectory and heating of in-flight particles are predicted for different operating parameters. The model is validated by experimental data in the literature. Effects of the mixing gas flow rates, particle sizes, and injection conditions on this process were investigated as well. 相似文献