Difference in particle characteristics and coating properties between spraying metallic and ceramic powder cored wires

The sprayed particles of metallic and cermet wires were collected to analyze the atomization state of the particles in arc spraying forming, the microstructure and properties of metallic and ceramic coatings were investigated and compared. Particle size analyzer was used for quantifying particle size. The XRD, SEM and optical microscope（OM） were used to analyze the phase composition and microstructure of the particles and coatings. From the experimental results, some difference of particle characteristics was established between the spraying metallic and ceramic cored wires, and the microstructure and properties of coatings depend strongly on the particles behaviors. The result shows that Fe-TiB2/Al2O3 composite coating has a high potential for abrasive wear applications.     

The bonding strength of powder coatings in gas-flame spraying with the hydrogen–oxygen flame

The equipment, procedure and the results of investigations of the bonding strength of gas-flame coatings with the substrate are described. The dependence of the bonding strength on the conditions of spraying with the powder materials using the hydrogen–oxygen flame is outlined.     

Influence of powder characteristics on structure and properties of Ni3Al fabricated by spark plasma sintering

Three kinds of Ni and Al powder mixtures with nominal composition Ni75Al25 were employed to prepare Ni3Al alloys by spark plasma sintering（SPS） process. The raw powders include fine powder, coarse powder and mechanically-alloyed fine powder. The effects of powder characteristics and mechanical alloying on structure and properties of sintered body were investigated by scanning electron microscopy（SEM）, X-ray diffraction（XRD）, bending test and Vickers hardness measurements. For all mixture powders near fully dense Ni3Al alloys （relative density〉99.5%） are obtained after sintering at 1150℃ for 5 min under 40 MPa. However a small fraction of Ni can be reserved for alloy from coarse powders. The results reveal that grain size is correlated with particle character of raw powder. Ni3Al alloy made from mechanically-alloyed fine powder has finer and more homogenous microstructure. The hardness of all alloys is similar varying from HV470 to 490. Ni3Al alloy made from mechanically-alloyed fine powder exhibites higher bending strength （1 070 MPa） than others.     

Study on the subsonic speed flame spraying coating of hydroxyapatite

A new method of preparation of biomaterial composite coating by the technique of subsonic thermal spraying was discussed in this paper. Ti6Al4V and pure Ti were chosen as substrate and sublayer material respectively and the working layer was sprayed with biomaterial hydroxyapatite (HAP), forming the composite coating. The experiments of heat shock and tensile strength showed that the bonding strength between coating and substrate is almost as same as that of specimen in which Ni/Al powder was adopted as sublayer. The phases of TiN, TiO2, and Ti2O3 were formed in the sublayer, which are free of toxic and have no side effects. The powder of working layer HAP was decomposed partly during spraying, but it can be solved by later treatment.     

Ground-based investigation of atomic oxygen effects on naked Ag and Ag with protective organic coating

Protective behavior of organic coatinge of alkyd,epoxy,urethane and siloxance applied to silver solar cell interconnects and erosion of Ag were investigated by exposure experiments to ground simulation atomic oxygen(AO).Evaluations of their protective properties were made through assessing their mass cfhange characteristics,chemical and physical changes to Ao attack.The specimens,after exposure were analyzed with SEM/EDAX and XPS.The results indicated that the silver is heavily etched.some coatings such as epoxy,alkd,urethane are seriously degraded or removed as volatile oxides and morphology of coatings changes.It is evident that siloxane coatings have excellent properties for anti-AO attack.The erosion product consists of silicon dioxide layer of compact texture and is left on the surface to provide adequate protection fro further attack by the energetic AO.     

Microstructure and bonding strength of Ni-based alloy coating

Glass molding dies often fail due to wear, oxidation and crack under the service condition of the melting glass above 1100℃ , existence of thermal shock or sliding contact friction. A repeated phase transformation may occur because the surface temperature of the die cavity exceeds eutectoid temperature during the service once the die is in contact with the hot glass. This, in turn, results in cracking on the die cavity surface, and finally, the service life of the die will be reduced[1]. Aust…     

Mechanical behavior of powder metallurgy steel—Experimental investigation and artificial neural network-based prediction model

Mechanical properties of high-density powder metallurgy (PM) steels have been evaluated using standard tests, and a theoretical model using the artificial neural network (ANN) has been developed. Various heat treatments were carried out to study their influence on mechanical properties, viz. endurance limit (EL), yield strength (YS), and hardness, and also on the carbon content in PM steel. The material containing 0.47% C that was quenched and tempered at 503 K (QT 503 K) showed the optimum combination of yield strength/ultimate tensile strength (YS/UTS) and EL. The ANN-based model showed excellent agreement with experimental results. Prediction models based on the ANN are demonstrated for YS as well as for the EL as a function of heat treatment (ranging from QT 400 K to QT 900 K) and percent carbon (%C) (between 0.1 and 0.5). This would help the materials engineer suitably design the heat-treatment schedule to obtain the desired/best combination of fatigue and strength properties.     

Effect of different incidence angles on bonding performance in cold spraying

The deformation behaviour of spray particles impacting upon a substrate under the oblique impact condition in cold spraying was investigated using finite element analysis(FEA)method.The effect of incidence angle of particle on the deformation of particle and substrate was examined.It is found that the contact area between the deformed particle and substrate decreases and the crater depth in the substrate reduces with increasing the tilting angle at the same impact velocity.The normal component of impact velocity takes an important role in the impacting process and formation of bonding.     

TiN coating on wall of holes and stitches by pulsed DC plasma enhanced CVD

1　INTRODUCTIONHardcoatingsdepositedbyplasmaenhancedchemicalvapordepositionhaveobtainedmoreinterestrecently .Sofar ,wearandcorrosion resistantcoat ingssuchasTiN ,TiCN ,TiC ,TiBN ,TiAlNcanbedepositedonvarioussubstratesbyPECVD[15] .Heimetal[6 ] investigatedthedepositionofTiAlNandTiAl NCcoatingsontoolsteelandhardmetalsubstrateinindustrialPECVD plant .Theirresultsshowedafinemorphologyandhighmicrohardnessupto 30 0 0Hvaswellasstrongadhesionof 30 4 0Nmeasuredinscratchtestcomparedwit…     

Sintering of WC-Co powder with nanocrystalline WC by spark plasma sintering

A 92WC-8Co powder mixture with 33 nm WC grains was prepared by strengthening ball milling and was then sintered by spark plasma sintering （SPS） at 1000-1200℃ for 5-18 rain under 10-25 kN, respectively. Movement of the position of low punch shown shrinkage of the sintered body began above 800℃. The shrinkage slowly rose as the temperature rose from 800 to 1000℃ and then quickly rose at above 1000℃ and then gradually rose at above 1150℃. The densities of the samples increased with an increase in sintering temperature, rapidly below 1100℃, and then gradually above 1100℃. WC grains grow gradually with increasing sintering temperature. The powder was sintered to near full density at 1100℃ for 5 rain under 10 kN. The best result of the sample with 275 nm WC grains and no pores was obtained at 1150℃ under 10 kN for 5 rain. The research found the graphite die had a function of carburization, which could compensate the sintered body for the lack of carbon, and had the normal microstructure.     

Boron carbide coating by electromagnetically accelerated plasma spraying

A new system of electromagnetically accelerated plasma spraying (EMAPS) consisting of a pulsed high-current arc-plasma gun and a large flow rate pulsed powder injector has been developed to synthesize a hard and dense coating of boron carbide (B₄C) with a high adhesion. The plasma gun with a co-axial cylindrical electrode configuration generates electromagnetically accelerated arc plasma with a typical velocity and maximum pressure of 1.5–3.0 km/s and 1 MPa, respectively, by discharging a pulsed high current of about 100 kA in peak and about 300 μsec of duration. The heating and accelerating of source powder are accomplished by injecting it into the inter-electrode space of the gun prior to the plasma generation using a newly developed pulsed powder injector that enables a gram of powder to be injected within 1 ms with precisely controlled time delay. With this system, hard B₄C coatings with a high adhesion and crystallinity were successfully formed on mirror-polished stainless (SUS304) substrates without a binder.     

Fe基非晶合金涂层的等离子喷涂成形特征

采用大气等离子喷涂法在Q235钢基材表面制备了Fe基非晶合金涂层，研究表明，涂层基本上由非晶相组成，在涂层中分布着少量的尺寸为2-5μm的淬态核结晶相，涂层中氧化物的含量较少。涂层由条带状粒子相互搭接、逐层堆积而成，具有典型的层状结构形貌。尺寸约为60μm的球形喷涂粒子在涂层中变形为高度尺寸约为6μm扁平状粒子，保证了高非晶相含量涂层的顺利形成。在涂层中的粒子边界还包含着少量的孔隙、微细的球形粒子等缺陷。涂层与基材、涂层中粒子问主要以机械结合为主，涂层与基材的结合区为涂层-基材体系中的最薄弱处。     

等离子喷涂人工骨涂层材料

等离子喷涂是一种常用的生物医用材料表面改性技术,被广泛应用于钛等金属人工骨的表面改性.为了满足人工骨涂层的临床应用需要,近年来发展了一些新的涂层材料和后处理工艺技术.利用火焰蒸汽处理技术对等离子喷涂羟基磷灰石涂层进行后处理,提高了涂层的结晶度,降低其在体液中的降解.经碱处理的等离子喷涂钛涂层,生物活性有了明显的改善.等离子喷涂硅灰石和硅酸二钙陶瓷是一类不同于传统磷酸钙系的新型生物活性材料,其性能和结构已被初步研究.同时介绍了等离子喷涂人工骨涂层材料在这几个方面的近期研究进展.     

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).     

等离子喷涂陶瓷涂层的应用

简述等离子喷涂陶瓷涂层的研究进展与现状,依据陶瓷涂层应用的分类,从等离子喷涂陶瓷涂层的耐磨涂层、热障涂层、耐蚀涂层、超导涂层、压电陶瓷涂层、生物活性涂层方面介绍了目前常用的等离子喷涂陶瓷材料的性能及其应用的研究现状。     

基于多层ANN的机器人等离子熔射智能化模型

分析了机器人等离子熔射过程的神经网络模型的实现方法,基于多层人工神经网络(antificial neural network,ANN)建立了等离子熔射过程的智能化模型.基于该模型,系统研究了等离子弧电流、熔射距离、机器人扫描间距和速度对主要涂层性能参数-残余应力和孔隙率的影响规律,并通过试验数据库的学习对涂层性能参数进行预测.结果表明,模型预测结果与试验结果有着很好的吻合,解决了工艺试验结果中仅有离散数据且难以全面反映等离子熔射工艺参数一涂层性能之间复杂非线性关系的难题.

Abstract：

The implementation of multi-layer artificial neural networks (ANNs) in robotic plasma spraying was discussed and an intelligent process model was constructed to fully describe the relationships between process parameters and coating properties. Influences of plasma arc current, spray distance, robot scanning space and scanning velocity on coating properties, i.e. residual stress and porosity, were systematically studied based on the present model. Prediction can be effectively carried out after the learning of the experimental database. Theoretical analysis shows the prediction results agree well with the experiments. It is favorable to fully investigate the complex and nonlinear relationships between processing parameters and coating properties as well as to overcome the limited information indicated by the discrete variable in the processing results.     

等离子喷涂镍基合金涂层的工艺优化

采用等离子喷涂工艺在GCr15钢基体上制备Ni60B合金涂层.通过正交试验法分析了喷涂工艺参数对涂层的结合强度的影响.其影响顺序自强至弱依次为功率、送粉速率、主气流量、喷涂距离.在功率为30 kW、送粉速率为30 9·min-1、主气流量为75 L·min-1、喷涂距离为105 mm时,涂层结合强度最高,达到59.311MPa.相结构分析结果表明,涂层材料未发生明显改变,保持了原始粉末性能.SEM观察结果表明,优化后的涂层组织更加紧密,质量明显提高.     

Effects of high-pressure plasma spraying for yttria-stabilized zirconia coating

Plasma spraying of yttria-stabilized zirconia was carried out under chamber pressures ranging from low (30 kPa) to high pressure (300 kPa) to investigate pressure effects on the plasma jet and to clarify the potential of high-pressure plasma spraying (HPPS) as a high performance coating tool. Plasma flame length and velocity of the particles were measured in situ, and the coating characteristics including its microstructure, density, and hardness were studied. A condensed plasma flame under high pressure facilitated sufficient melting of zirconia particles, resulting in high deposition efficiency and a dense coating with improved hardness, in spite of reduced particle velocity. High-pressure plasma spraying was found to be suitable for thermal spraying of high-melting-point materials such as zirconia.     

超音速等离子喷涂层的接触疲劳失效研究进展

介绍了超音速等离子喷涂层在服役过程中常见的4种疲劳失效形式(表面磨损、点蚀、分层和剥落)及其发生的机理。综述了涂层结构完整性对疲劳失效的影响,即粗糙度、孔隙率和微裂纹对疲劳失效的作用机制。总结了不同的服役条件(接触应力、润滑状态)对疲劳磨损失效的影响规律,展望了接触疲劳失效机制的研究方向,指出应从涂层内部结构和服役条件来揭示疲劳损伤机理。