电爆喷涂技术在材料表面制备涂层的研究进展

综述了电爆喷涂技术在材料表面制备涂层的研究进展和应用.给出了电爆喷涂技术的特点,喷涂设备的工作原理以及喷涂材料的种类;详细讨论了放电参数、喷涂材料与基体材料的几何尺寸、喷涂室气压、复合涂层等因素对涂层质量的影响;列举了电爆喷涂技术的实际应用;进一步分析了将来需要研究的问题.     

冷喷涂技术研究进展及其在舰船领域的应用

冷喷涂作为一种低温固态成型技术,具有基材热影响小、粉末材料不易氧化、沉积效率高等特点,可用于金属防护涂层制备、零部件修复和增材制造。首先从冷喷涂系统、喷涂材料、喷涂工艺3个方面介绍了冷喷涂技术的特点;其次总结了近年来冷喷涂技术在粉末材料设计、涂层结合机理、组织结构与性能调控方面的研究进展;然后,详述了冷喷涂技术在国外海军舰船领域的应用情况;最后,简述了冷喷涂技术在我国海军舰船领域的研究及应用情况,并对其未来发展方向进行了展望,以期提高我国海军舰船装备腐蚀防护及维修保障能力。     

非金属材料表面冷喷涂金属化的研究现状及展望

冷喷涂是一种快速发展的固态粉末沉积技术,具有喷涂温度低、沉积效率高、制造速度快等特点,在金属涂层制备、受损零部件修复、增材制造等方面已有广泛的研究与应用。传统冷喷涂工艺的基体材料一般是金属材料,其沉积过程的机理研究也较为成熟。近年来,随着众多工业领域对复合材料的需求进一步提升,通过冷喷涂技术在非金属材料表面制备金属涂层(表面金属化)受到了不同领域众多研究者的关注。总结了目前已报道的使用冷喷涂工艺在高分子和陶瓷等非金属材料表面制备金属涂层的相关结果,围绕几种常用的高分子和陶瓷基体材料,分析了非金属基体材料上冷喷涂沉积金属涂层的结合机理,并在此基础上讨论了冷喷涂工艺参数和材料参数对非金属材料表面冷喷涂金属化的影响。     

金属泡沫材料研究进展

综述了金属泡沫材料的各种制备方法。液相法制备金属泡沫材料包括气体吹入法、固体发泡剂法和固体—气体共晶凝固法、熔模铸造法、渗流铸造法、喷射沉积法以及粉末加压熔化法等制备方法。采用金属粉末烧结法、浆料发泡法等制备工艺可以从固相制备金属泡沫材料。电沉积法以及气相沉积法可用于制备高孔隙率的金属泡沫材料。最后简要总结了金属泡沫材料的应用。     

热喷涂纳米涂层制备方法及材料研究现状和展望

综述了热喷涂纳米涂层的制备方法现状及所用材料的发展情况,介绍了溶液等离子喷涂(SPS)、冷气动力喷涂(CGDS)、高速火焰喷涂(HVOF)技术制备纳米涂层的优势、纳米粉末材料的制备方法及发展趋势,指出纳米涂层制备的主要关键在于解决纳米粉末的输送技术和涂层制备过程中抑制纳米颗粒的长大趋势.纳米涂层的研究对推动热喷涂技术应用有着十分重要的作用.     

电爆喷涂中工艺参数对涂层性能的影响

电爆喷涂技术能够快速、方便地在玻璃等非金属表面制备金属涂层。通过对不同工艺参数下电爆喷涂实验样品的测试与分析,得到了工艺参数与涂层性能之间的关系。结果表明,电爆喷涂过程中,当电容器初始电压从10kV逐渐增大到20kV、金属丝直径由1mm逐渐减小到0.5mm、回路电感由10.8μH逐渐减小到3.9μH时,能够使金属丝的受热更加充分,爆炸产生的金属微粒的平均粒径更小,温度更高,飞行速度更快,因而形成的涂层更加致密、均匀,涂层电阻最小达到0.235mΩ。     

热辐射粒子参数测量系统的喷涂方法和材料适用性的研究

针对自行开发的基于窗口调制与比色测温技术的热喷涂参数测量系统,研究了常用喷涂方法和喷涂材料对有效信号的平均强度和单次采样捕获有效粒子数的影响,检验了其适用性.结果表明,本系统对等离子喷涂(APS)的适用性良好,可用于常用金属与陶瓷粉末粒子的参数测量,而超音速火焰喷涂(HVOF)尽管也适用于大多数合金与金属陶瓷粉末的测量,但仍表现出一定的材料选择性,有必要采用更高灵敏度的光敏器件以进一步改善该系统对不同喷涂方法和材料的适用性.     

冷喷涂制备复合材料涂层研究现状

鉴于目前冷喷涂技术制备复合材料涂层受到国内外越来越多学者的关注,本文在大量文献分析的基础上对冷喷涂制备复合材料涂层进行了分类和总结。首先,探讨了喷涂前粉末准备和喷涂工艺参数对复合材料涂层的影响;其次,归纳了冷喷涂制备的金属-金属、金属-陶瓷、金属-金属间化合物以及纳米复合材料涂层等研究成果;最后,分析了冷喷涂制备复合材料涂层的应用前景和当前存在的主要问题。     

喷雾干燥YPSZ纳米结构热喷涂粉末材料制备及表征

YPSZ纳米结构粉末材料的研究是热喷涂制备YPSZ纳米结构涂层必须首先进行研究的问题。本文采用喷雾干燥方法制备适合于热等离子体喷涂的YPSZ纳米结构粉末原料,同时采用等离子体喷涂制备涂层。利用扫描电子显微镜分析晶粒大小、颗粒形貌,X射线衍射分析相组成,对喷雾干燥后粉末进行热重-差热分析,测定粉末的松装密度、振实密度及流动性。结果表明制备的YPSZ粉末材料具有实心、流动性好、松装密度高、振实密度高、球形度高、单斜相少等优点,采用热等离子体喷涂沉积制备YPSZ纳米结构涂层。     

反应火焰喷涂TiC/Fe复合涂层显微结构研究

采用前驱体碳化复合技术制备Ti-Fe-C系反应喷涂复合粉末,通过反应火焰喷涂技术成功制备了TiC/Fe基金属陶瓷复合涂层.利用XRD和SEM对喷涂粉末和涂层的成分、组织结构进行了分析,考察了喷涂粉末粒度、Ti的加入方式对涂层组织结构的影响.研究结果表明:所制备的TiC/Fe复合涂层由不同含量TiC颗粒分布于晶粒内部而形成的晶内型复合强化片层组织叠加而成,TiC颗粒呈纳米级;喷涂粉末粒度较大时,制备的涂层中出现有害相Fe2Ti,片层厚度较大,孔隙率高;以纯Ti粉为Ti源制备的喷涂粉末和以TiFe粉为Ti源制备的喷涂粉末相比较,其涂层中硬质相TiC含量较少,孔隙率较大.     

Visualization and modeling for water atomization of low melting point alloy

Liquid metal fragmentation by impinging fast water spray, so called water atomization, is widely used to produce metal powders efficiently. In the present paper, we conduct the high-speed visualization experiments and theoretical modeling for elucidating the mechanism of fragmentation and solidification processes, which are essentially important to control the metal powder characters. We successfully visualize the detailed sequential events from the water spray ejection, freely dropped molten metal of 42Sn-58Bi, followed by their collision, metal fragmentation in liquid phase, and solidification, leading to revealing the fragmentation processes as the impact of water spray and the vapor explosion. Quantified metal particle size convinces that the water atomization simultaneously proceeds fragmentation of metal in liquid phase with solidification. The experimental results of size distribution and mean diameter well validate the proposed physically-consistent theoretical modeling for the prediction of particle size.     

Magnetic properties of sintered sendust alloys using powders granulated by spray drying method

The iron-silicon-aluminum alloys (particularly Sendust) have been widely used in applications requiring high saturation flux density, low coercive force and high electrical resistivity. For this reason they have been promising for magnetic thin film heads, however, they are too hard and brittle to be made into thin films by rolling, or into three-dimensional products of complex shape by mechanical working or a conventional powder metallurgy process. The reduction in the size and weight of devices that can be accomplished through the use of Sendust has had an important effect on technical development. In this report, magnetic characteristics of Sendust ring samples produced by the powder metallurgy process with spray drying were investigated. After gas-atomized Sendust powders were mixed with paraffin compounds, these powders were granulated by the spray drying method using organic binder consisting of polyvinyl alcohol (PVA) and plasticizer in the range from 0.1 to 0.5 wt% of PVA, in order to improve the powder flowability and mechanical strength of compacted bodies. Results show that the present method is an excellent process for producing near-net-shaped parts with high performance and high dimensional precision after sintering.     

Fabrication of alloy nanopowders by the electrical explosion of electrodeposited wires

Electrical wire explosion technique has been successful in the production of various pure metal powders. However, the process has the obvious limitation that alloy and intermetallic powders are difficult to produce due to the unavailability of their thin wire form. In this study, a novel method by which various alloys and compounds can be produced was suggested utilizing electrodeposition and wire explosion process. Al-Cu and Cu-Ni alloy nanopowders were fabricated by the electrical explosion of Cu-deposited Al and Ni wires. Ni-Cu nanopowders were composed of Ni- and Cu-solid solutions. Al-Cu wire explosion produced various phases in the order of Al, Al₂Cu, Al₃Cu₄ as the copper layer became thicker. It is demonstrated that the suggested method could provide means to produce numerous alloys and intermetallic nanopowders.     

Review Environmentally friendly coatings using carbon dioxide as the carrier medium

The use of supercritical or liquid carbon dioxide as a medium for delivering coating systems is attracting much interest because of concerns over the environmental effects of volatile organic compound (VOC) emissions from conventional coatings. Significant reductions in VOC emissions can be achieved by replacing some or all of the organic solvent by CO₂ in spray coatings. Technical and commercial benefits are also claimed for these systems, including improved coating efficiency and operating cost savings. In this review, the range of current and potential applications achievable using CO₂-based coatings is discussed. In addition to spray coatings onto a variety of substrate surfaces, CO₂ processes can be used to produce controlled particle size powders for use in powder coatings and also for the coating of preformed particles such as metal powders and pharmaceuticals for controlled release in drug delivery. Use of CO₂ in spin coating and microlithography offers the potential for significant waste reduction. Specific substrates where use of CO₂ can be beneficial include the treatment of building stone and wood treatment. CO₂ can aid surface impregnation of substrates because of its high diffusivity and the potential for substrate swelling.     

A new generation of engineering materials produced by Spray Forming

Many new engineering materials can now be produced by the group of new processes covered by the general name of Spray Forming. The materials are made directly from molten metal of virtually any composition and range from light strip, composites and coated products through spray forgings to heavy centrifugally sprayed deposits weighing individually up to 4 tonnes. Some are at an early stage of development, while others are already in commercial production.It is shown that the properties of the products depend greatly upon the spray density used in the individual processes. A low spray density can give materials that benefit from rapid solidification with resulting high mechanical properties, whereas high spray densities give products that are very near to theoretical density and can be produced at high throughputs.     

气体放电式丝电爆制备纳米粉中大颗粒的形成

为认识丝电爆制备纳米粉过程中大颗粒的形成特征,利用石英探针直接收集金属丝各个部分形成的粉末并进行显微分析。结果表明,丝端部形成的粉末中微米级大颗粒比例要比丝中间部分粉末中的比例大;随着初始电压的升高,丝端部与丝中间部分的粉末中微米级大颗粒比例都减小,并最终达到一致。气体放电式丝电爆过程中,丝中间部分主要通过焦耳加热的作用沉积能量;而丝端部还会受到等离子体中高温粒子的高速撞击作用,也会向丝端部沉积一部分能量。     

Rapid hard tooling by plasma spraying for injection molding and sheet metal forming

Amidst the harsh competition over the development of new products around the world, rapid prototyping, especially rapid tooling methods have received widespread attention. Amongst the rapid hard tooling methods, thermal spraying can manufacture metal molds without limitation of pattern size. However, it has the disadvantage that only soft metals with low melting points such as zinc alloy can be sprayed to original mold, such as a rapid prototyping model or a natural material pattern, due to their lack of heat resistance and shrinkage of spray metals. So the wear resistance of spray tool is poor, it can be used only for trial or small-lot production. In this study, attempts were made to improve the heat resistance by using composite materials made of ceramic and metal powders as the sprayed original mold materials, and using stainless steel, tungsten carbide alloy, iron–nickel–chromium alloy with excellent wear resistance as spraying materials, respectively. The results show that injection molding spray mold and sheet metal forming spray die can be made by transferring from natural patterns and rapid prototyping models. As the durability and dimensional accuracy of the sprayed tools has sharply improved, the tools can be used for mass production.     

高压电场中金属丝段电爆产物的形成

应用金属丝段与电极非接触电爆设备,通过改变电场电压和电极间距进行系列电爆金属铜丝试验,对爆炸后产物进行分离称量,并利用显微镜观察各种产物的形貌特点,结果表明,丝段进入高压电场后,通过丝端部与电极之间的气体放电将大电流导入而发生电爆。等离子体旁路作用使湮没在等离子体内部一部分或整根金属丝段不发生电爆残留下来。电极间距较长时,释放在金属丝段上的能量密度减小,不能够使整个金属丝段气化爆炸。适合制备超细粉的电极间距范围随电场电压的增加而扩大,对应电场电压4kV、5kV和6kV时,适合制备超细粉的电极间距范围分别为23．3—25．2mm、22．7—27．3mm和22．7—58．6mm。     

Preparation of ultra-fine copper powder and its lead-free conductive thick film

In this paper, non-agglomerated monodispersed ultra-fine copper metallic powders have been synthesized with chemical reduction method. Fine lead-free glass powders were also prepared by solid synthesis process. Thick film paste prepared by above-mentioned copper metallic powders and lead-free glass powders was applied as conductive paste of MLCC. Mixture of glass and zinc oxide give the thick film a high adhesion strength which is attributed to the rough interface from interfacial reaction between glass and chip, and a good densification. Diffusion of metal between copper thick film and nickel thick film is clear. Ni-Cu solid solution appears under high temperature firing.     

Herstellung HVOF gespritzter,feinststrukturierter Cermetschichten unter Verwendung von feinen WC‐12Co Pulvern

Manufacturing of HVOF sprayed, finest structured cermet coatings using fine WC‐12Co powders The continuous increase in productivity and performance of modern sheet metal forming processes combined with the employment of novel, high strength materials cause high wear on tool systems. Coating technologies like thermal spraying provide a high potential to functionalize and to protect the surface of forming tools. However, it has to be ensured that the high shape and dimensional accuracy of the tool contour is preserved after the application of a wear protective coating. This aim cannot be achieved using currently applied, thermally sprayed coating systems with conventional, coarse grained microstructure. To solve this problem, novel finest structured coatings have been developed in this study by thermal spraying of fine WC‐12Co powders using the HVOF technique. For this purpose the influence of varying HVOF combustion gas compositions on the spray process as well as on the corresponding coating properties has been investigated. Next to a high surface quality the focus was placed on achieving coatings with high hardness and corresponding high wear resistance, low porosity as well as a good adhesive strength on the substrate material.