In Flight Properties of W Particles in an Ar-H<Subscript>2</Subscript> Plasma

An in-flight properties measurement performed on W particles, injected into thermal plasma generated by an inductively coupled RF plasma torch, is presented. The measured surface properties of the particles along the centerline of the plasma plume are expressed by means of temperature and velocity maps, within the domain formed by individual particle’s diameters and their distances from the torch exit. The influence of some of the processing parameters (plate power, carrier gas flow rate, spray chamber pressure) on particle properties is discussed for both individual particles and the resultant integral spray plume characteristics. The results so obtained appear to confirm the suitability of the RF plasma process for the deposition/production of W coatings/deposits.     

Relationships between microstructure and electrical properties of RF and DC plasma-sprayed titania coatings

Relationships between electrical properties of thermally sprayed titania coatings and their microstructures have been investigated. It is well known that the quality and properties of the plasma-sprayed coatings are strongly dependent on the in-flight particle characteristics, which directly influences the plasma-sprayed coating microstructures. As far as possible, a broad range of microstructures was produced by using various processes of plasma spraying with different powder size ranges and variation of the plasma operating parameters. The two plasma-spraying processes consisted of direct current (DC) and radio frequency (RF) plasma spraying. The major concern of the study was that plasma-sprayed parameters influence also the stoichiometry of the titania coating resulting in a large variation of their electrical properties. It is the reason why coatings with identical stoichiometry were compared. The comparison between RF and DC plasmasprayed titania coatings highlighted that electrical resistivity was directly linked to the quality of the contact between the splats and their density through the titania plasma-sprayed coatings.     

树脂基复合材料用陶瓷涂层防护性能分析

采用等离子喷涂铝粉作为打底材料在碳纤维增强聚酰亚胺复合材料（PMC）基体上制备了Al2O3和ZrO2轻质陶瓷防护涂层，测试了涂层的剪切结合强度、耐热循环性能、抗冲蚀性能、隔热性能。结果表明，等离子喷涂铝粉作打底层的涂层系统，性能优于电弧喷铝或电弧喷锌作打底层的涂层系统。带有Al2O3涂层的试样失重不到基体材料失重的1／3，Al2O3和ZrO2陶瓷涂层都可以为聚酰亚胺复合材料基体提供有效的冲蚀防护。Al2O3和ZrO2陶瓷涂层都可以为聚酰亚胺复合材料基体提供有效的隔热防护，ZrO2涂层隔热性能优于Al2O3涂层。     

Hydroxyapatite coatings for biomedical applications deposited by different thermal spray techniques

Thermally sprayed hydroxyapatite (HAp) coatings are widely used for various biomedical applications due to the fact that HAp is a bioactive, osteoconductive material capable of forming a direct and firm biological fixation with surrounding bone tissue.Bioceramic coatings based on nanoscale HAp suspension and microscale HAp powder were thermally sprayed on Ti plates by high-velocity suspension flame spraying (HVSFS) technique and atmospheric plasma spraying (APS) as well as high velocity oxy fuel spraying (HVOF) technique. HVSFS is a novel thermal spray process developed at IMTCCC, for direct processing of submicron and nano-sized particles dispersed in a liquid feedstock.The deposited coatings were mechanically characterized including surface roughness, micro hardness and coating porosity. The bond strength of the layer composites were analyzed by the pull-off method and compared for the different spray techniques. Phase content and crystallinity of the coatings were evaluated using X-ray diffraction (XRD). The coating composite specimen and initial feedstock were further analysed by scanning electron microscope (SEM) and rheology analysis.     

Plasma spraying of combustion flame spheroidized hydroxyapatite (HA) powders

Tailoring powder characteristics to suit the plasma spray process can alleviate difficulties associated with the preparation of hydroxyapatite (HA) coatings. Commercial HA feedstock normally exhibit an angular morphology and a wide particle size range that present difficulties in powder transport from the powder hopper to the plasma spray gun and in nonuniform melting of the powders in the plasma flame. Hence, combustion flame spheroidized hydroxyapatite (SHA) was used as the feedstock for plasma spraying. Spherical particles within a narrow particle size range are found to be more effective for the plasma spray processes. Results show coatings generated from spheroidized HA powders have unique surface and microstructure characteristics. Scanning electron microscope (SEM) observation of the coating surface revealed well-formed splats that spread and flatten into disc configurations with no disintegration, reflecting adequate melting of the HA in the plasma and subsequent deposition consistency. The surface topography is generally flat with good overlapping of subsequent spreading droplets. Porosity in the form of macropores is substantially reduced. The cross-section microstructure reveals a dense coating comprised of randomly stacked lamellae. The tensile bond strengths of the SHA coatings, phase composition, and characteristics of the coatings generated with different particle sizes (125 to 75 μm, 45 to 75 μm, 20 to 45 μm, and 5 to 20 μm) showed that a high bond strength of ∼16 MPa can be obtained with SHA in the size range from 20 to 45 μm. This can be improved further by a postspray treatment by hot isostatic pressing (HIP). However, larger particle size ranges exhibited higher degrees of crystallinity and relatively higher HA content among the various calcium phosphate phases found in the coatings.     

High-power hybrid plasma spraying of large yttria-stabilized zirconia powder

To testify to the advantage of large ceramic powder spraying, numerical simulations and experimental studies on the behavior of large yttria-stabilized zirconia (YSZ) powder in a high-power hybrid plasma spraying process have been carried out. Numeric predictions and experimental results showed that, with the high radio frequency (RF) input power of 100 kW, the most refractory YSZ powder with particle sizes as large as 88 μm could be fully melted and well-flattened splats could be formed. A large degree of flattening (ξ) of 4.7 has been achieved. The improved adhesive strength between the large splat and the substrate was confirmed based on the measurement of the crack density inside of the splats. A thick YSZ coating >300 μm was successfully deposited on a large CoNiCrAlY-coated Inconel substrate (50×50×4 mm in size). The ultradense microstructure without clear boundaries between the splats and the clean and crack-free interface between the top-coat and the bond-coat also indicate the good adhesion. These results showed that highpower hybrid plasma spraying of large ceramic powder is a very promising process for deposition of highquality coatings, especially in the application of thermal barrier coatings (TBCs).     

超音速等离子喷涂制备WC-12Co涂层的性能特点

超音速等离子喷涂由于喷射粒子的飞行速度(400～500m/s)相对于普通等离子喷涂(＜200m/s)有了大幅提高,所制备的WC-12Co涂层具有更高的显微硬度和结合强度.用SEM和XRD分析了两种不同等离子喷涂工艺获得的涂层的相结构和显微组织,结果表明超音速等离子喷涂WC-12Co涂层综合性能要优于普通等离子喷涂.     

等离子喷涂陶瓷涂层后氧化处理的研究

对比研究了后氧化处理、封孔和退火、真空退火对大气等离子喷涂 (Al/Ni Cr2 O3 )陶瓷涂层硬度、结合强度等性能的影响。结果表明 ,合理的后氧化能够明显改善涂层性能 ,且氧的扩散是发挥作用的重要因素之一。     

A comparative study of high velocity oxygen fuel,vacuum plasma spray,and axial plasma spray for the deposition of CoNiCrAlY bond coat alloy

In the aerospace field as well as in the stationary gas turbine field, thermally sprayed coatings are used to improve the surface properties of nickel-super-alloys materials. Coatings are commonly used as bond coat and antioxidation materials (mainly MCrAlY alloys) and as thermal barrier coatings (mainly yttria partially stabilized zirconia). The purpose of the current study was to assess the properties of thermally sprayed bond coat CoNiCrAlY alloys comparing the performance of three different techniques: vacuum plasma spray (VPS), high velocity oxygen fuel (HVOF), and axial plasma spray (AxPS). The quality of the deposited films has been assessed and compared from the point of view of microstructural (porosity, oxide concentration, unmelted particles presence) and mechanical (hardness) characteristics. The surface composition and morphology of the coatings were also determined. Specific efficiency tests were performed for the three examined technologies. The highest quality coatings are obtained by VPS, but also high velocity oxygen fuel and AxPS sprayed films have interesting properties, which can make their use interesting for some applications.     

An investigation on plasma spraying with artificial bone powder and bonding characteristics of coating

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先进陶瓷涂层结构调控及其在固体氧化物燃料电池中的应用

等离子喷涂技术可以对陶瓷涂层的微观结构进行调控设计,因此在制备固体氧化物燃料电池方面具有独特的优势。基于等离子喷涂方法,可以直接制备或经过后处理获得致密的电解质涂层。采用等离子喷涂技术也可以制备高性能的多孔阳极和阴极,并可对钙钛矿结构阴极材料的成分和晶体结构进行调控。文中介绍了目前国内外采用涂层制备电池的方法,主要探讨了热喷涂方法制备电解质涂层的特点,对存在的问题和可行思路进行了讨论,并探讨了基于提高三相反应界面长度来制备高性能电极的方法。由于固体氧化物燃料全电池各功能层都有可能通过热喷涂方法制备,因此该方法在固体氧化物燃料电池结构设计具有巨大的潜力。     

Properties of Reactive Plasma Sprayed TiB2-TiC0.3N0.7 Based Composite Coatings with Cr Addition and Laser Surface Treatment

Thick TiB₂-TiC_0.3N_0.7 based composite coatings were deposited by reactive plasma spraying (RPS) successfully in air. The influence to the coating properties (morphology, Vickers microhardness and corrosion resistant property) with Cr addition in the thermal spray powder and TiB₂-TiC_0.3N_0.7 based coatings treated by laser were investigated. The phase composition, structure and properties of composite coatings were studied using XRD, SEM, EDS, Vickers microhardness and electrochemical testers. The results show that the Vickers microhardness values and the density of laser surface treated coatings are improved significantly. The Cr addition in the thermal spray powder can increase the density, improve the wettability of ceramic phases, uniform the phase distribution and enhance the corrosion-resistant property of coatings. However, due to lower microhardness of metal Cr than ceramic phases in coatings, the Vickers microhardness values of plasma sprayed coatings and plasma sprayed coatings with laser surface treatment are a little lower than that of each coating without Cr addition in the thermal spray powder.     

Base-metal saturation of refractory carbide coatings produced by enhanced ceramic jets in electrothermally exploded powder spray

Tungsten carbide and tantalum carbide were sprayed onto substrates of mild steel by the electrothermally exploded powder spray (ELTEPS) process. High-speed x-ray radiography revealed that tungsten-carbide jets of molten particles guided inside a nozzle exhibited denser flow than unguided jets at the substrate. The velocity of the jet was approximately 800 m/s at the early stage of jetting. The ceramic coatings obtained from the guided spray consisted of carbides of a few to tens of micrometers in size, which were saturated by the base metal up to the top of the coating. The coatings exhibited diffusion of the sprayed ceramics and base metal at the interface of the deposit and substrate. The enhancement of the jet flow formed a microstructure of the ceramic coating, which was saturated by the base metal even without post heat treatment.     

面向等离子体材料钨厚涂层的制备及表征

等离子体喷涂技术在面向等离子体材料钨涂层的制备中占据主导地位,本实验采用CuMo/MoW作为涂层的中间过渡层,分别以结晶钨粉和羰基钨粉为原料,用大气等离子体喷涂技术在CuCrZr合金基体(110 mm×130mm)上制备了3-4 mm厚的3种钨涂层.对钨涂层微观组织、力学性能和热学性能研究表明,羰基钨粉制备的钨涂层的综合性能优于结晶钨粉,且薄涂层的结合强度优于厚涂层.优化喷涂工艺后,金相法测得钨涂层孔隙率＜2％,涂层的结合强度最大值为10 MPa,EDS测得氧含量为6％左右,纯钨层热导率最大值为12.52 W/(m.K),涂层氧含量过高导致涂层热导率显著降低.研究表明采用大气等离子体喷涂技术在铜合金上制备3～4mm厚的钨涂层是可行的,该技术可为下一步低成本、高性能厚钨涂层的制备奠定基础.     

Numerical Analysis of Radio-Frequency Inductively Coupled Plasma Spheroidization of Titanium Metal Powder Under Single Particle and Dense Loading Conditions

Metals and Materials International - In order to allow more practical prediction of RF (radio-frequency)–ICP (inductively coupled plasma) spheroidization results of titanium metal powder,...     

高温树脂基复合材料防护用轻质陶瓷涂层的制备

研究了采用Ni-3％Al粉末和纯铝、纯锌作为打底材料在碳纤维增强聚酰亚胺复合材料(PMC)基体上制备Al2O3轻质陶瓷防护涂层的可行性,测试了涂层的剪切结合强度和耐热循环性能。结果表明,等离子喷涂Ni-3％Al粉末会对PMC基体造成破坏,不适合于作为PMC基体上的打底材料。电弧喷铝也会对基体造成一定程度的破坏,结合强度和耐热循环性能较低。采用低电压、小电流电弧喷锌,可以获得和基体结合良好打底涂层,涂层剪切结合强度达10．45MPa。在其上制备的Al2O3陶瓷防护涂层耐热循环性能良好。     

超音速电弧喷涂铝涂层的耐蚀特性

采用光学显微镜、电子扫描显微镜研究了超音速电弧喷涂铝涂层的显微组织结构的及喷涂粒了状态;采用拉伸试验和硬度计测试了涂层结合强度、三度,采用中性盐雾试验对铝涂 耐腐蚀性进行实验,结果表明超音束电弧喷涂铝涂层孔隙率低、组织致密,结合强度和硬芳较高、耐腐蚀性能优越,铝、Ａｃ铝俣金涂层的耐腐蚀性能几乎相同。     

单枪共喷异种粒子涂层结构及结合强度分析

选用Cr3C2-NiCr粉末、Ni包MoS2粉、Ni60粉末以及3种粉末的混合粉末,采用超音速火焰喷涂技术制备涂层试样.研究了异种粒子共喷对涂层的显微组织结构特征和涂层的结合强度的影响.研究结果表明:与喷涂单一粒子相比,单枪共喷异种粒子在堆叠过程中更容易形成孔隙,造成涂层组织疏松;与单一粒子涂层相比,单枪共喷异种粒子涂层的结合强度明显下降;异种粒子共喷涂层的结合强度与异种粒子的配比相关.     

Plasma spray forming of tungsten coatings on copper electrodes

Both direct current dc plasma and radio frequency induction plasma were used to deposit tungsten coatings on copper electrodes. Fine tungsten powder with mean particle size of 5 um and coarse tungsten powder with particle size in the range from 45 um to 75 um were used as plasma spray feedstock. It is found that dc plasma is only applicable to spray the fine tungsten powder and induction plasma can be used to spray both the coarse powder and the fine powder. The tungsten coating deposited by the induction plasma spraying of the coarse powder is extremely dense. Such a coating with an interlocking structure and an integral interface with the copper substrate demonstrates high cohesion strength and adhesion strength.     

Plasma Sprayed Coating Using Mullite and Mixed Alumina/Silica Powders

Plasma sprayed ceramic coatings are widely used for thermal barrier coating applications. Commercially available mullite powder particles and a mixture of mechanically alloyed alumina and silica powder particles were used to deposit mullite ceramic coatings by plasma spraying. The coatings were deposited at three different substrate temperatures (room temperature, 300?°C, and 600?°C) on stainless steel substrates. Microstructure and morphology of both powder particles as well as coatings were investigated by using scanning electron microscopy. Phase formation and degree of crystallization of coatings were analyzed by x-ray diffraction. Differential thermal analysis (DTA) was used to study phase transformations in the coatings. Results indicated that the porosity level in the coatings deposited using mullite initial powder particles were lower than those deposited using the mixed initial powder particles. The degree of crystallization of the coatings deposited using the mixed powder particles was higher than that deposited using mullite powder particles at substrate temperatures of 25 and 300?°C. DTA curves of the coatings deposited using the mixed powders showed some transformation of the retained amorphous phase into mullite and alumina. The degree of crystallization of the as sprayed coatings using the mixed powder particles was significantly increased after post deposition heat treatments. The results indicated that the mechanically alloyed mixed powder can be used as initial powder particles for deposition of mullite coatings instead of using mullite powders.