共查询到17条相似文献,搜索用时 515 毫秒
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采用等离子喷涂方法,在不同喷涂距离、主气流量和喷涂功率下制备硅灰石涂层.使用扫描电镜观察了涂层的微观形貌,研究了喷涂工艺参数对涂层结构的影响.结果表明,在较大主气流量下,随着喷涂距离增加,涂层粒子扁平化程度降低,涂层内孔隙逐渐增多;在较小主气流量下,涂层粒子扁平化程度随喷涂距离增加呈现先增加后减小的趋势.主气流量增加,涂层致密,粒子扁平充分.喷涂功率增加,粒子熔化好,涂层致密;但随喷涂功率进一步增加,涂层中出现较多的圆形孔隙.喷涂工艺参数对涂层结构的影响主要通过影响熔融粒子的温度和速度所致. 相似文献
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大气等离子射流中粒子飞行行为的试验测量 总被引:1,自引:0,他引:1
为考察等离子熔射中粉末的飞行过程,应用芬兰Oseir公司等离子喷涂在线监测和分析设备SprayWatch对射流中粒子的温度、飞行速度和粒子流量进行了测量,探讨了等离子弧电压、电流、功率以及送粉量等参数对粒子飞行状态的影响.结果表明:同等功率下,电流对粒子速度的影响高于电压,电压对粒子流量的影响高于电流,电压、电流对粒子温度则呈现交替重要的影响;在电流400A、电压50V下粒子流量随送粉量的增加呈现低-高-低的"山峦"状变化,反映了粒子飞行路径和分布的变化. 相似文献
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采用超音速等离子喷涂可低成本、高效率制备钛涂层。采用响应曲面法(RSM)中的Box-Behnken(BBD)设计分析了Ar流量、功率、喷涂距离3个因素与超音速等离子射流中钛粒子飞行速度和温度的交互性,利用SEM和显微硬度计研究了钛涂层的微观结构和显微硬度。结果表明:建立的线性模型可靠,喷涂距离对粒子飞行速度和温度影响最大,且随喷涂距离增加粒子飞行速度减小温度增加,而Ar流量和功率对粒子飞行速度和温度的影响与喷涂距离相反。超音速等离子喷涂制备出的钛涂层硬度较低,且呈多孔结构,随粒子飞行速度增加孔隙率降低。 相似文献
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从冷喷涂粒子速度与温度协同问题出发,归纳总结了影响冷喷涂涂层质量的主要因素,并在此基础上,重点综述了喷嘴结构、气体类型与性质、粒子形态与材料等工艺参数与粒子速度-温度的作用关系.提高喷枪喷嘴扩张段膨胀比,改善黏性效应,提高高速区面积,使用高热扩散系数材料的喷嘴,均能够显著改善粒子速度-温度的协同效果.在工业应用中,可采用喷丸辅助冷喷涂、激光辅助冷喷涂、静电辅助冷喷涂、真空冷喷涂等新型复合沉积技术,实现高强低塑性喷涂粒子材料的沉积成形.最后,就如何深入研究速度-温度高质量协同并获得高质量涂层进行了展望. 相似文献
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A three-dimensional computational fluid dynamic (CFD) analysis using Fluent V5.4 was conducted on the in-flight particle behavior
during the plasma spraying process with external injection. The spray process was modeled as a steady jet issuing from the
torch nozzle via the heating of the are gas by an electric are within the nozzle. The stochastic discrete model was used for
the particle distribution. The particle temperature, velocity, and size inside the plasma plume at a specified standoff distance
have been investigated. The results show that carrier gas flow rate variation from 2 standard liters per minute (slm) to 4.0
slm can increase the centerline particle mean temperature and mean velocity by 10% and 16%, respectively, at the specified
standoff distance. A further increase of the carrier gas flow rate to 6 slm did not change the particle temperature, but the
particle velocity was decreased by 20%. It was also found that an increase in the total arc gas flow rate from 52 slm to 61
slm, with all other process parameters unchanged, resulted in a 17% higher particle velocity, but 6% lower particle temperature.
Some of these computational findings were experimentally confirmed by Kucuk et al. For a given process parameter setting,
the kinetic and thermal energy extracted by the particles reached a maximum for carrier gas flow rate of about 3.5–4.0 slm. 相似文献
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Chao Zhang Abdoul-Fatah Kanta Chang-Jiu Li Hanlin Liao 《Surface & coatings technology》2009,204(4):463-469
In-flight particle characteristics (surface temperature and velocity upon impact) are among the most important parameters which influence the coating microstructures and properties in atmospheric plasma spraying (APS) process. The purpose of this paper is to study hydrogen fraction used as secondary plasma forming gas on the in-flight particle surface temperature and by extension on the coating microstructures of atmospheric plasma-sprayed 8 mol% yttria stabilized zirconia electrolyte coatings implementing in particular artificial neural networks (ANN). Then, the predicted in-flight particle characteristics were on the one hand compared to experimental values and on the other hand correlated to some of the coating structural attributes (porosity and gas specific permeability). The predicted results were in good accordance with the experimental data. Results showed that the H2 flow rate had obvious influence on particle temperature and had almost no significant effect on particle velocity. Increasing the particle temperatures induced dense coating microstructure and improved the gas-tightness performance. 相似文献
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Using laser anemometry, laser fluxmetry, and statistical two-color pyrometry, the velocity, number flux, and surface temperature
distributions of alumina and zirconia particles in dc plasma jets have been determined inflight for various spraying parameters.
The flux measurements emphasized the importance of the carrier gas flow rate, which must be adjusted to the plasma jet momentum
depending on the arc current, nozzle diameter, gas flow rate, and gas nature. It has also been shown that the particle trajectories
depend both on the particle size and injection velocity distributions and that the position and tilting of the injector plays
a great role. The particle size drastically influences its surface temperature and velocity, and for the refractory materials
studied, only the particles below 45 μm in diameter are fully molten in Ar-H2 (30 vol%) plasma jets at 40 kW. The morphology of the particles is also a critical parameter. The agglomerated particles
partially explode upon penetration into the jet, and the heat propagation phenomenon is seriously enhanced, particularly for
particles larger than 40 μm. The effects of the arc current and gas flow rate have been studied, and the results obtained
in an air atmosphere cannot be understood without considering the enhanced pumping of air when the plasma velocity is increased.
The Ar-He (60 vol%) and Ar-H2 (30 vol%) plasma jets, when conditions are found where both plasma jets have about the same dimensions, do not result in
the same treatment for the particles. The particles are not as well heated in the Ar-He jet compared to the Ar-H2 jet. Where the surrounding atmosphere is pure argon instead of air (in a controlled atmosphere chamber), he radial velocity
and temperature distributions are broadened, and if the velocities are about the same, the temperatures are higher. The use
of nozzle shields delays the air pumping and increases both the velocity and surface temperature of the particles. However,
the velocity increase in this case does not seem to be an advantage for coating properties. 相似文献
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Sudharshan Phani Pardhasaradhi Vishnukanthan Venkatachalapathy Shrikant V Joshi Sundararajan Govindan 《Journal of Thermal Spray Technology》2008,17(4):551-563
Cold gas dynamic spraying (CGDS), a relatively new thermal spraying technique has drawn a lot of attention due to its inherent
capability to deposit a wide range of materials at relatively low-operating temperatures. A De Laval nozzle, used to accelerate
the powder particles, is the key component of the coating equipment. Knowledge concerning the nozzle design and effect of
process parameters is essential to understand the coating process and to enable selection of appropriate parameters for enhanced
coating properties. The present work employs a one-dimensional isentropic gas flow model in conjunction with a particle acceleration
model to calculate particle velocities. A laser illumination-based optical diagnostic system is used for validation studies
to determine the particle velocity at the nozzle exit for a wide range of process and feedstock parameters such as stagnation
temperature, stagnation pressure, powder feed rate, particle size and density. The relative influence of process and feedstock
parameters on particle velocity is presented in this work. 相似文献
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Jose Colmenares-Angulo Kentaro Shinoda Travis Wentz Wei Zhang Yang Tan Sanjay Sampath 《Journal of Thermal Spray Technology》2011,20(5):1035-1048
Deliberate particle state variations were performed using atmospheric plasma spray (APS) and high-velocity oxy-fuel flame
spraying (HVOF) to create a set of first-order process maps. Particle states were measured simultaneously using five in-flight
particle sensors: DPV-2000, Accuraspray, SprayWatch, TDS, and SprayCam. While the sensors use similar methods for calculating
particle characteristics, absolute values of temperature and velocity were considerably different. Process map trends among
sensors are in agreement for the HVOF process, but differ when using plasma spray at high total gas flow conditions. After
understanding the stochastic nature of particle detection, an open loop feedback control algorithm was implemented to achieve
similar particle states with different hydrogen gas flow rates. The resulting particle state window measured by three different
sensors under select fixed hydrogen flow rates was significantly narrowed. 相似文献
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S. V. Joshi 《Journal of Thermal Spray Technology》1993,2(2):127-130
Plasma-sprayed WC-Co coatings are used extensively in a variety of wear-resistant applications. The quality of these sprayed
coatings depends greatly on the temperature and velocity of the powder particles impacting the substrate. Because it is both
expensive and difficult to experimentally determine these particle parameters, the present study deals with a theoretical
investigation of particle heatup and acceleration during plasma spraying of WC-Co based on a recently developed model. The
effect of WC-Co particle size on the evolution of particle temperature and velocity is examined through calculations performed
under typical spraying conditions. The implications of the powder particles, assuming an off-axis trajectory during their
traverse through the plasma flame, are also discussed. 相似文献
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等离子喷涂ZrO2热障涂层工艺参数优化设计 总被引:10,自引:0,他引:10
为了深入研究等离子喷涂ZrO2粒子的飞行特征与涂层性能之间的关系,采用三水平四因素正交试验法对主气、辅气、电流及喷涂距离等4个主要参数进行了优化设计,并采用DPV2000热喷涂在线监测仪测定了ZrO2粒子的飞行特征参数,通过IA32定量金相分析软件对涂层的孔隙率进行了测试。结果表明,影响ZrO2粒子温度的主要因素为主气和辅气,影响ZrO2粒子飞行速度的主要因素为喷涂距离和辅气。 相似文献