Principles and droplet size distributions of various spraying methods: a review

Spraying refers to the process of forming small droplets of a liquid and dispersing them in air or on the surface of an object. Spraying is ubiquitous because it enables a liquid widely and uniformly dispersed. The existing spraying methods can be broadly categorized as ultrasonic, liquid compression, and two-phase nozzle-based. These different methods utilize different principles, with advantages and disadvantages. Thus, it is necessary to understand how different methods are suited to the applications of interest. In particular, the droplet size plays a significant role. Many studies have been conducted to characterize different spraying methods, but little systematic organization and summarization with respect to the droplet size has been done. Herein, we introduce the most widely used spraying methods and explain their spraying principles, fields of use, and appropriate operating environments. We focus on the droplet size aspect. This review is likely to be useful in the design and development of spraying devices.

     

梅钢1420平整机组湿平整过程喷淋流场的计算

运用计算流体动力学(CFD)的大型商用软件Fluent对平整液喷射流场进行数值计算和分析。主要计算和分析了在喷射梁上的两个喷嘴与喷射梁垂直和呈一定角度时的速度场、压力场分布情况,对设计喷射梁和理解喷淋流场具有实际意义。     

逆顺流式与逆流式无填料喷雾冷却塔的试验研究

根据雾化冷却原理,建立了逆顺流式无填料喷雾冷却塔和逆流式无填料喷雾冷却塔,在介绍了30t/h试验用逆顺流式和逆流式无填料喷雾冷却塔的结构和性能的基础上,通过试验对两种冷却塔的冷却性能进行了研究,试验结果表明:当设计风量相同时,逆流式无填料喷雾冷却塔的实测风量比逆顺流式无填料喷雾冷却塔的实测风量大5.5%;在试验工况基本相同的条件下,逆流式无填料喷雾冷却塔的进出水温差较逆顺流式无填料喷雾冷却塔大0.5℃,逼近度约小0.9℃,冷却效率大20%,且其冷却效率最大值为53.4%.     

沥青洒布量智能测试系统的研制

沥青洒布量智能测试系统是一种基于单片机的嵌入式系统,该系统为路面上的沥青洒布施工提供方便和保证准确度。该文介绍了系统的原理,给出了系统的软硬件设计,实现了在8位LED数码管上显示沥青洒布量和流量、车速和泵速、洒布宽度和料号等参数,并通过RS232串口实现了单片机与PC机的通信。主要特点：在8个数码管上分时复用显示2组参数,软件上预先定义了一些功能键,对系统进行标定,达到较高的精度。     

新型材料改性方法——常温超音速冷喷涂制备功能涂层

介绍一种新型材料表面改性技术－冷喷涂技术，即气体在常温下或在有限加热温度下，利用超音速气流将涂层粉末喷射到基板形成保护涂层。相对热喷涂技术而言，其不存在高温氧化、气化、晶化等影响涂层性能的效应出现，具有独到之处。结合工程实际简化建模，并完成气、固两相射流的流场计算结果。定量研究了冷喷涂试验中两相射流流对涂层效果的影响程度。还对该试验装置进行了锌粉、陶瓷粉的膜制备试验，取得了预期效果。     

热喷涂用免喷砂涂料的研究

热喷涂方法日趋成熟,但热喷涂预处理阶段仍然存在着劳动强度大、能耗大、污染严重、设备复杂、施工困难等缺点。本文鉴于喷砂喷涂在预处理阶段存在的困难以及我国社会生产现状,研制出一种免喷砂热喷涂用涂料,这样就省略了繁杂的预处理工序,使传统热喷涂得以改善,提高了生产力。     

超音速火焰喷涂微米和纳米结构WC-12Co涂层及其性能

以纳米和微米级WC-12Co粉末为原料,采用超音速火焰喷涂(HVOF)方法在16Mn基体上制备了两种涂层.利用X射线衍射仪对喷涂粉末及涂层进行了相结构分析,用扫描电镜对喷涂粉末、磨粒磨损前后的涂层表面形貌进行了观察,探讨了粉末结构、涂层的组织和结构以及抗磨粒磨损的性能.结果表明:WC-12Co粉末结构对涂层的组织结构影响非常显著,微米WC-12Co粉末中的WC的分解基本上得到了抑止,而纳米结构的粉末由于出现了WC的部分分解,导致了纳米涂层的抗磨粒磨损性能相对于微米涂层提高不多,但是与基体16Mn相比,两种涂层均表现出优异的抗磨粒磨损性能.     

Effects of the nozzle design on the properties of plasma jet and formation of YSZ coatings under low pressure conditions

How to control the quality of the coatings has become a major problem during the plasma spraying. Because nozzle contour has a great influence on the characteristic of the plasma jet, two kinds of plasma torches equipped with a standard cylindrical nozzle and a converging-diverging nozzle are designed for low pressure plasma spraying(LPPS) and very low pressure plasma spraying(VLPPS). Yttria stabilized zirconia(YSZ) coatings are obtained in the reducing pressure environment. The properties of the plasma jet without or with powder injection are analyzed by optical emission spectroscopy, and the electron temperature is calculated based on the ratio of the relative intensity of two ArⅠspectral lines. The results show that some of the YSZ powder can be vaporized in the low pressure enlarged plasma jet, and the long anode nozzle may improve the characteristics of the plasma jet. The coatings deposited by LPPS are mainly composed of the equiaxed grains and while the unmelted powder particles and large scalar pores appear in the coatings made by VLPPS. The long anode nozzle could improve the melting of the powders and deposition efficiency, and enhance the coatings' hardness. At the same time, the long anode nozzle could lead to a decrease in the overspray phenomenon. Through the comparison of the two different size's nozzle, the long anode is much more suitable for making the YSZ coatings.     

等离子熔射制模过程中皮膜温度场实验研究

开展了等离子熔射制模过程中环行向外、环行向内两种熔射路径的皮膜温度场的实验研究，得出前者的温度低于后者的实验结果，该实验结果与模拟结果一致；对三维汽车覆盖件基体等离子熔射过程中的温度分布规律进行探讨，得到三维熔射基体不同形状特征处的温度分布规律，从而为建立合理的熔射制模工艺提供了依据。     

40CrNiMoA调质钢件的喷熔工艺研究

氧-乙炔火焰粉末喷熔工艺是近年来发展起来的一种新型的热喷涂工艺。本文研究了采用氧-乙炔火焰粉末喷熔修复磨损超差的航空零部件的方法,提出了40CrNiMoA调质钢件的喷涂修复工艺。     

基于试验与仿真联合分析的喷涂机器人轨迹精度可靠性研究

采用链驱动的喷涂机器人易于实现本体的轻量化、末端高灵活度与正压防爆系统设计,从而满足家具、钢结构等一般涂装行业对喷涂机器人工作空间与腕部灵活度的要求,深入分析链驱动机器人的运动可靠性对喷涂质量和效率的提高具有重要意义。针对链驱动喷涂机器人的运动可靠性问题,采用一种基于试验与仿真联合分析的机器人末端轨迹精度可靠性分析方法。以旋量法为基础建立了喷涂机器人本体和喷枪的运动学模型,从工业机器人的操作臂性能和运动规律的角度出发,研究了喷涂机器人运动精度的影响因素。分析了链驱动喷涂机器人的优缺点和末端轨迹精度的影响状况,并结合机器人本体的运动学参数,建立了基于随机变量的喷涂机器人运动误差模型。通过试验结果的分析来确定影响喷涂机器人运动误差的随机变量的分布特征,从而对机器人末端轨迹精度的运动可靠性进行更加精确的仿真分析。最后,通过喷涂机器人工作平台对末端轨迹精度的运动误差进行试验验证并与传统的仿真分析方法进行对比,结果显示该分析方法更准确。研究成果为进一步分析喷涂机器人的机构优化、轨迹规划和漆膜质量提供试验基础和理论依据。     

Different Approaches to the Investigation and Testing of the Ni-Based Self-Fluxing Alloy Coatings—A Review. Part 2: Microstructure,Adhesive Strength,Cracking Behavior,and Residual Stresses Investigations

After presenting general facts about Ni-based self-fluxing alloy coatings and describing the wear and corrosion studies in Part 1, Part 2 of the article deals with the review and systematization of the investigations on behavior of these coatings exposed to external mechanical loading (cracking behavior, adhesive strength, fatigue), residual stresses, and microstructure (particle state, phases, porosity, dilution, dissolution) considering the period from 2000 to 2013. The following deposition technologies are included: flame spraying, high-velocity oxy/air fuel spraying, detonation gun spraying, electric arc spraying, plasma spraying, plasma-transferred arc welding, and laser cladding. In addition to the review of investigations on microstructure and effects of external loading and residual stresses, reference is also given to papers describing the application of the Ni-based self-fluxing coatings, as well as to those in which these coatings were used as a reference material or an addition to obtain a composite coating.     

耐磨防滑热喷涂粉芯线材的研究

金属粉芯线材在热喷涂领域中具有调节成分范围宽、价格低、研制新材料方便等待点。本工作对研制的电弧喷涂用耐磨防滑粉芯线材喷涂层进行了结合强度、显微硬度、耐磨性、防滑性能的测试。结果表明：涂层Ｚ１６、Ｚ１７均具有良好的耐磨防滑性能,其中Ｚ１６的综合性能最佳。     

应用于喷雾降尘的喷嘴设计浅析

根据粉尘粒度及雾化效果参数,综合匹配喷嘴结构参数与喷雾压力,设计了旋流片结构的二次雾化喷嘴。     

等离子喷涂技术研究与发展现状

本文从等离子喷涂设备、新型功能涂层、与等离子喷涂相关的测量技术等几个方面,综述了等离子喷涂技术的研究与发展现状。     

有限元法在热喷涂技术中的应用和发展

综述了有限元法在热喷涂技术中的应用.对有限元法作了总体的介绍,通过对国内外部分学者在热喷涂技术上数值模拟工作的介绍,阐述了有限元法在热喷涂技术中的应用现状,总结了有限元法在热喷涂技术方面应用的优势及不足,并展望了有限元法在热喷涂技术中的发展.     

The erosion and abrasion characteristics of alumina coatings plasma sprayed under different spraying conditions

A series of plasma sprayed alumina coatings was evaluated regarding their erosion and abrasion characteristics. The coatings were deposited under different spraying conditions, using a commercial axial injection plasma spray system, and with powders of different grit sizes and crystallinity. A sintered bulk alumina and a conventionally sprayed coating, produced by a radial injection air plasma spray technique, were tested as reference materials. To evaluate the importance of energy input the coatings were produced using two different torch nozzle sizes and gas mixtures with a varied amount of hydrogen. The erosion and abrasion results indicate that hydrogen concentration, nozzle size and precursor powder type and size influence the tribological characteristics of the coatings. The wear resistance of the coatings seems to benefit from an increase in hydrogen concentration or torch nozzle size. The effect of precursor powder size on the wear resistance was more complex but indicates that sapphire powders of medium precursor sizes are advantageous to ordinary plasma spraying powders of alumina.     

喷涂功率对NiCr-Cr3C2涂层表面自由能及其摩擦性能的影响

利用超音速等离子喷涂技术制备了不同喷涂功率条件下的NiCr-Cr3C2涂层,结合表面自由能理论研究了其表面摩擦学性能。利用Owens-Wendt几何平均法计算了涂层的表面自由能及其分量。对比发现,涂层孔隙率、显微硬度和摩擦因数均随着喷涂功率的变化而变化,且其变化趋势与极性分量均表现出一定的相似性。分析表明,受喷涂功率的影响,喷涂粒子的温度和速度对涂层表面分子间作用力产生影响,从而间接改变了涂层表面的自由能,并且自由能及其分量的改变,会直接影响NiCr-Cr3C2涂层表面的摩擦学特性。     

超声速等离子喷涂Ni60A涂层的滚动接触疲劳寿命*

制备高质量的超声速等离子喷涂Ni60A涂层,并研究该涂层的滚动接触疲劳性能及寿命。通过正交试验对Ni60A涂层的4个主要喷涂工艺参数(喷涂电压、喷涂电流、Ar气流量和喷涂距离)进行优化设计,通过分析孔隙率和显微硬度值的大小,综合评价喷涂层质量。利用Image J2x孔隙率计算软件计算涂层孔隙率,利用扫描电镜分析Ni60A粉末和喷涂层的微观结构,采用显微硬度计测定涂层的显微硬度,利用RM-1接触疲劳/磨损多功能试验机对涂层进行不同载荷条件下的接触疲劳试验,并建立Weibull失效概率图。结果表明,通过正交试验可以获得高质量的超声速等离子喷涂Ni60A涂层,超声速等离子喷涂Ni60A涂层的最优喷涂工艺参数为：喷涂电压170 V,喷涂电流370 A,Ar气流量110 L/min,喷涂距离110 mm,通过最优参数制备得到的Ni60A涂层的孔隙率为1.05%,显微硬度为1 086 HV_0.2;在不同接触应力水平下,Ni60A涂层的寿命服从Weibull分布,通过Weibull失效概率图可以在一定范围内预测某一工作载荷下涂层的接触疲劳寿命。