Influence of Zn and Mg Alloying on the Corrosion Resistance Properties of Al Coating Applied by Arc Thermal Spray Process in Simulated Weather Solution

In this study,Al–Zn and Al–Mg coatings were deposited on steel substrates by an arc thermal spray process.X-ray diffraction and scanning electron microscopy were used to characterize the deposited coatings and corrosion products.Open circuit potential（OCP）,electrochemical impedance spectroscopy,and potentiodynamic studies were used to assess the corrosion characteristics of these coatings after exposure according to the Society of Automotive Engineers（SAE）J2334 solution of varying durations.This solution simulates an industrial environment and contains chloride and carbonate ions that induce corrosion of the deposited coatings.However,the Al–Mg alloy coating maintained an OCP of approximately-0.911 V versus Ag/Ag Cl in the SAE J2334 solution even after 792 h of exposure.This indicates that it protects the steel sacrificially,whereas the Al–Zn coating provides only barrier-type protection through the deposition of corrosion products.The Al–Mg coating acts as a self-healing coating and provides protection by forming Mg_6Al_2（OH）_（16）CO_3（Al–Mg layered double hydroxides）.Mg_6Al_2（OH）_（16）CO_3has interlocking characteristics with a morphology of plate-like nanostructures and an ion-exchange ability that can improve the corrosion resistance properties of the coating.The presence of Zn in the corrosion products of the Al–Zn coating allows dissolution,but,at the same time,Zn_5（OH）_6（CO_3）_2and Zn_6Al_2（OH）_（16）CO_3are formed and act to reduce the corrosion rate.

Characteristics of non-thermal AC arcs in multi-arc generator

To obtain large-volume non-thermal arc plasma(NTAP), a multiple NTAP generator with three pairs of electrodes has been developed. The arc plasma characteristics, including dynamic process, spatial distribution, and rotation velocity in the discharge zone, were investigated by high speed photograph and image processing methods. The results showed that the dynamic behaviors and spatial distribution of the arc plasma were strongly related to the electrode configuration.A swirl flow of multi-arc plasma was formed by adjusting the electrode configuration, and a steady luminance area was clearly observed in the center of the discharge zone. Moreover, the size of the luminance area increased by decreasing the gas flow rate. The electrical connection in series could be formed between/among these arc columns with their respective driving power supplies in the multi-arc dynamic evolution process. An approximately periodical process of acceleration and deceleration of the arc rotation velocity was observed in the multi-arc generator with swirl flow configuration. In general, the mean velocity of arc rotation was higher in the multi-arc generator with swirl flow configuration when a pair of electrodes driven by a power supply were opposite to each other rather than adjacent.

Thermal behavior of B_4 Cparticles under plasma arc powder surfacing condition

The effect of plasma arc powder surfacing process on the amount of B4C particles in the coating and the thermal behavior of B4C particles in different surfacing stages has been investigated.The results showed that the feeding rate of B4C partiles is the most important factor affecting the amount of B4C particles in the surfacing coating among all the surfacing parameters,and the most part of B4C Particles in the coating is nto the remainders of original solid B4C particles,but the consolidation products of the unmelted liquid B4C globules in the pool.The results also showed that the B4C particles would not be melted in the plasma arc column, their melting process mainly takes place in the anode spot region on the surface of the pool when surfacing current is less than 200A.

Preparation of micro-arc oxidation coatings on magnesium alloy and its thermal shock resistance property

In the NaAlO2-Na2SiO3 compound system, the ceramic coatings were prepared on magnesium alloy by micro-arc oxidation. The morphology, phase composition, and thermal shock resistance of the ceramic coatings were studied by scanning electron microscope, X-ray diffraction and thermal shock tests, respectively. The results showed that the ceramic coating contains MgO, MgAl2O4, as well as a little amount of MgESiO4. The thickness of the ceramic coatings increases with the current density increasing, when the current density is 12 A·dm^-2, the thermal shock resistance of the produced ceramic coating is the best. The hardness of the ceramic coating is up to 10 GPa or so.

Tri-Arc双丝焊“Γ”形电弧及其促进方法

Tri-Arc双丝三电弧焊通过中间第3弧的M弧重新分配焊接热输入,实现高熔覆率低热输入焊接.M弧与主电弧耦合,在整个动态周期表现为“Γ”形和“μ”形及其镜像形态.该文研究“Γ”形电弧的形成机理和热输入调控机制,结果表明,“Γ”形态由“μ”形态转变而来,熔滴振荡引起焊丝末端间距的变化,从而促进耦合电弧“Γ”形态的形成,此时M弧不作用于母材,比“μ”形电弧焊接热输入更低.为提高Tri-Arc双丝焊接低热输入效果,在维持导电嘴末端到工件距离不变的前提下,提高焊枪枪体抬升距离从而改变焊丝末端间距.当导电嘴长度由30 mm增加至35 mm时,随着焊枪抬升,“Γ”形电弧作用时间逐渐增加,能更好地促进电弧热分配,降低Tri-Arc双丝焊接热输入,从而降低熔池最高温度,获得更小宽高比和更小熔深的焊缝.

Effects of deposition parameters on microstructure and thermal conductivity of diamond films deposited by DC arc plasma jet chemical vapor deposition

The uniform diamond films with 60 mm in diameter were deposited by improved DC arc plasma jet chemical vapor deposition technique. The structure of the film was characterized by scanning electronic microcopy(SEM) and laser Raman spectrometry. The thermal conductivity was measured by a photo thermal deflection technique. The effects of main deposition parameters on microstructure and thermal conductivity of the films were investigated. The results show that high thermal conductivity, 10.0 W/(K·cm), can be obtained at a CH4 concentration of 1.5% (volume fraction) and the substrate temperatures of 880-920 ℃ due to the high density and high purity of the film. A low pressure difference between nozzle and vacuum chamber is also beneficial to the high thermal conductivity.

Thermal Shock Resistances of FeMnCr/Cr_3C_2 Coatings Deposited by Arc Spraying

Arc spraying with the cored wires was applied to deposit FeMnCr/Cr3C2 coatings on low carbon steel substrates, namely FM1, FM2 and FM3. Thermal shock resistances of the coatings were investigated to assess the influence of Cr3C2 content on thermal shock resistance. Characteristics of the coatings under thermal cycling test were studied by optical microscopy, field emission scanning electron microscope （FE-SEM） and energy dispersion spectrum （EDS）, X-ray diffraction （XRD）. The experimental results show that hardness of the coatings increases, bonding strength decreases slightly with increase of the Cr3C2 content of the coatings. As a result, FM2 coating possesses the best thermal shock resistance, attributing to its better thermal expansion matches and wettability than those of FM3 coating, less oxide rate than that of FM1 coating restraining from cracks formation and propagation in coatings.

HVAF-ARC喷涂Cr_2C_3活性功能涂层性能的研究

本文采用HVAF-ARC喷涂系统制造的NiCrFe-Cr2C3活性功能涂层。通过金相组织研究、SEM检测、X射线衍射以及涂层结合强度分析,证明其具有良好的组织形貌;同时HVAF-ARC所制备的Cr2C3合金涂层的性能相对于普通电弧喷涂涂层的性能在同等试验条件下优于普通高速电弧喷涂。

利用加速量热仪(ARC)研究热分析动力学反应机理

从动力学基础方程推导出绝热条件下ARC热分析动力学方程,与传统的DTA动力学方程比较,ARC理论模型更接近于化学过程工业.以SM型和RM型含能材料为样品进行热分析测试,运用新的理论模型分别计算出了SM型和RM型两种样品的活化能ESM=247.55kJ.mol-1,ERM=138.46kJ.mol-1和指前因子ASM=4.26×1023S-1,ARM=4.20×1012S-1.

HVAF-ARC喷涂系统的工艺性能研究

介绍了超音速电弧喷涂技术(HVAF-ARC)的原理和特点,喷涂系统进行工艺性能研究。研究分析了5种工艺参数对于喷涂结合强度和涂层的微观组织的影响。

HVAF-ARC涂层在电站锅炉省煤器防护中的研究

本文采用HVAF-ARC喷涂系统制造的NiCrTi活性功能涂层。研究电站锅炉省煤器防护涂层的金相组织研究、SEM检测、X射线衍射以及涂层显微硬度。

Energy Balance in DC Arc Plasma Melting Furnace

In order to treat hazardous municipal solid waste incinerator＇s （MSWI） fly ash, a new DC arc plasma furnace was developed. Taking an arc of 100 V/1000 A DC as an example, the heat transfer characteristics of the DC arc plasma, ablation of electrodes, heat properties of the fly ash during melting, heat transfer characteristics of the flue gas, and heat loss of the furnace were analyzed based on the energy conservation law, so as to achieve the total heat information and energy balance during plasma processing, and to provide a theoretical basis for an optimized design of the structure and to improve energy efficiency.

Analysis of Effects of the Arc Voltage on Arc Discharges in a Cathode Ion Source of Neutral Beam Injector

A hot cathode bucket ion source is used for the EAST（experimental advanced superconducting tokamak）neutral beam injector.The thermal electrons emitted from the surface of the cathode are extracted and accelerated by the electric field formed by the arc voltage,which is applied between the arc chamber of the ion source and the cathode.This paper analyzes the effects of arc voltage on the arc discharge in a hot cathode high current ion source.

Prediction of cooling time t8/5 in twin wire submerged arc welding of intermediate thickness plate

Twin wire submerged arc welding （SAW） is widely used in oil or gas line pipe fabrication because of its high productivity. To investigate the strength and toughness of the heat-affected zone （HAZ） in twin wire SAW, the cooling time t8/5 of the coarse grained zone must be studied. The authors presented a method of predicting the cooling time in twin wire SAW of intermediate thickness plate. Based on Rosenthal analytical solutions, an energy factor was introduced to describe the energy contribution of the two wires, equations of thermal cycle and cooling time in twin wire SAW of both thick, and thin, plates were developed. Weighting factors determined by actual thickness and critical thickness were adopted to represent the thermal cycle and cooling time of intermediate thickness plate through linear interpolation with thick, and thin, plate solutions. The predicted cooling time for an intermediate thickness plate was verified experimentally, and the predicted results agreed therewith.

Characteristics of Gliding Arc Discharge Plasma

A gliding arc discharge plasma and its characteristics are described. Analysis of the production principle of the plasma is presented. Some experimental results about two novel types of the gliding arc plasma generator have been obtained. These types of gliding arc plasma axe potentially usable in the chemical industry and environmental engineering.

Synthesis of Fullerene by Pyrolysis of Acetylenein Thermal HF-Plasma

Carbon soot containing fullerene was continuously produced in volume by pyrolyzing acetylene in thermal HF-Plasma. The characteristics of the carbon soot and C60 were analyzed by thtransmission electron microscopy, UV/visible, IR and Raman spectroscopy. The results show that the main ingredients of the carbon soot with size of about 25 nm are amorphous carbon, graphite and fullerene. The fullerene yield in carbon soot is about 2.5 g·h^-1. Compared with the graphite arc discharge method, the acetylene thermal plasma method is a preferential one for synthesis of fullerene.

Three-Dimensional Numerical Modeling of an Ar-N_2 Plasma Arc Inside a Non-Transferred Torch

A three-dimensional numerical model is developed to study the behaviour of an argon-nitrogen plasma arc inside a non-transferred torch. In this model, both the entire cathode and anode nozzle are considered to simulate the plasma arc. The argon-nitrogen plasma arc is simulated for different arc currents and gas flow rates of argon. Various combinations of arc core radius and arc length, which correspond to a given torch power, are predicted. A most feasible combination of the same, which corresponds to an actual physical situation of the arc inside the torch, is identified using the thermodynamic principle of minimum entropy production for a particular torch power. The effect of the arc current and gas flow rate on the plasma arc characteristics and torch efficiency is explained. The effect of the nitrogen content in the plasma gas on the torch power and efficiency is clearly detected. Predicted torch efficiencies are comparable to the measured ones and the effect of the arc current and gas flow rate on predicted and measured efficiencies is almost similar. The efficiency of the torch, cathode and anode losses and core temperature and velocity at the nozzle exit are reported for five different cases.

基于ARC的自制硝铵炸药热危险性评价研究

为了提高公安机关处置涉爆案事件的理论水平与技术能力,基于氧平衡设计并配制了典型配方的硝铵炸药,开展了ARC量热分析,通过动力学计算,得到了自制硝铵炸药的T_(D24)、T_(NR)、T_(SADT)等特征参数。测试结果表明:硝酸铵/柴油/木粉体系硝铵炸药的绝热分解过程分为两个阶段,负氧平衡状态时的初始分解温度和绝热温升分别为140.2℃和3647.81℃,热稳定性最差;硝酸铵/柴油/铝粉体系较硝酸铵/柴油/木粉体系的初始分解温度略有上升,绝热温升明显增大,表现为稳定性稍高,爆炸性更强;负氧平衡状态时硝酸铵/柴油/木粉体系硝铵炸药的自加速分解温度为89.34℃,因自分解放热引发热失控,从而导致火灾、爆炸事故发生的可能性较大,应尽量避免硝铵炸药在负氧状态下的存储。

Discharge Characteristics of DC Arc Water Plasma for Environmental Applications

A water plasma was generated by DC arc discharge with a hafnium embedded rodtype cathode and a nozzle-type anode. The discharge characteristics were examined by changing the operation parameter of the arc current. The dynamic behavior of the arc discharge led to significant fluctuations in the arc voltage and its frequency. Analyses of the high speed image and the arc voltage waveform showed that the arc discharge was in the restrike mode and its frequency varied within several tens of kilohertz according to the operating conditions. The larger thermal plasma volume was generated by the higher flow from the forming steam with a higher restrike frequency in the higher arc current conditions. In addition, the characteristics of the water plasma jet were investigated by means of optical emission spectroscopy to identify the abundant radicals required in an efficient waste treatment process.

基于SYSWELD的大厚板窄间隙双丝埋弧焊热过程数值模拟

基于60 mm厚Q345R钢,开展了窄间隙双丝埋弧焊焊接试验,得到了合理的工艺参数,焊缝成型平整均匀无任何缺陷.通过SYSWELD有限元软件对大厚板窄间隙双丝埋弧焊焊接热过程进行数值模拟分析,模拟的熔池宽与高和实际相比,误差率均控制在5%以内,并利用热电偶装置测得热影响区热循环曲线与模拟的热循环曲线变化趋势基本一致,具有升温快,降温慢的特点,验证了该模型的有效性.为后续利用该模型,进一步探究不同参数或边界条件对于大厚板窄间隙双丝埋弧焊焊接热过程与应力-应变规律提供理论指导.