未来高性能发动机活塞环的热喷涂发展

等离子喷涂由于适用材料广泛，能够满足许多摩擦学性能，因而在欧洲得到极大的发展。喷涂参数对于改进涂层结构，从而改进涂层磨损、结合力、内聚力及耐腐蚀性能非常重要。首先研究了喷涂用等离子气体，然后通过试验优选了所有喷涂参数。除喷涂参数外，粉末成份对涂层摩擦学性能也有较大影响。为降低活塞环-缸套摩擦副磨损，对几种粉末进行了对比试验。通过理想化试验与发动机试验相结合，表征了一些钼基涂层的摩擦学行为。     

活塞环气缸套的喷钼及钼合金表面处理

热喷涂 (或称熔射 )是指采用专用设备把固体材料熔化 (或软化 )迅速喷射到工件表面形成涂层的法 ,一般喷涂有以下分类 :热喷涂燃烧法火焰喷涂线材喷涂棒材喷涂粉末喷涂超音速喷涂爆炸喷涂电加热法电弧喷涂等离子喷涂常压等离子喷涂低压或真空等离子喷涂感应等离子喷涂线爆喷涂用于活塞环、气缸套的喷涂主要有火焰喷涂、等离子喷涂及线爆喷涂等。喷涂材料为钼或钼基合金 ,经过喷涂处理后的活塞环、气缸套 ,明显提高了抗熔着磨损能力。这是因为钼的熔点高 ( 2 630℃ ) ,且其喷涂处理后的表面孔隙率适度 ,从而改善贮油性能 ,即便油膜破裂时 ,氧…     

激光处理的等离子喷涂Cr2O3涂层的摩擦学特性

通过对等离子喷涂涂层在Ｎｄ－ＹＡＧ激光处理前和处理后的磨损量对比，研究了激光处理对等离子喷涂Ｃｒ２Ｏ３陶瓷薄涂层的影响，为此，用陶瓷／ＳＡＥ４６２０钢以线接触配对进行了环形试样磨损试验，还讨论了磨损机制和因激光处理引起的涂层中有关孔隙率，显微结构和涂层结合情况的变化。     

高压汽轮机等离子喷涂MCrAlY涂层的热机械性能

文章研究了两种不同的涂层：真空等离子喷涂的ＮｉＣｏＣｒＡｌＹＴａ和电镀的ＮｉＣｏＣｒＡｌＹＴａ，这些涂层都是沉积在ＡＭ３单晶合金上的，试验研究了喷涂后的单晶试样的拉伸和蠕变性能，从拉伸试验中测定了ＤＢＴＴ，蠕变试验是在圆柱型试样上和在薄的平板试 进行的，所有涂层的均在试验前后进行了检测分析。     

超音速等离子喷涂技术与装备

超音速等离子弧喷涂技术是重要的表面工程技术之一。与其它的喷涂技术相比较,它具有生产效率高、涂层质量好的特点。可以熔化金属、碳化物陶瓷和氧化物陶瓷等材料。乌克兰科学院巴顿电焊研究所研究开发的超音速等离子喷涂技术与装备具有显著的技术优势,其最大工作电流达400A;粉末颗粒飞行速度达到750m／s;各种材料涂层的结合强度大于55MPa;沉积率大于60％;金属粉末的送粉速度高达50kg／h。     

真空等离子喷涂氧化铝——氧化钛涂层

真空等离子喷涂,可对许多材料在很宽范围的基体上,作为一种高质量的涂层的来源正在获得大家的认同。在真空下喷涂形成的涂层邮极好的耐磨损、抗腐蚀和高温特性。在本研究中,为了使喷涂的陶瓷涂层的气孔率得到最大程度的减少,使用了控制真空度的喷涂方法将氧化铝－－氧化钛喷涂于石墨上。实验是在使用统计学的分数因子设计参数研究而进行的。操作参数是围绕Taguchi设计的实验典型参数变化的,Taguchi设计的实验表明,等离子 涂参数的范围和它们对测量涂层性能的影响,Taguchi设计研究了三个影响等离子喷涂的变量对测量灵敏度的影响：电流、主气流量和辅气流量来评价。涂层的质量用涂层厚度、气孔率、粗糙度和显微硬度来评价。本文讨论了喷涂参数对涂层质量的影响。用高功率和高辅气流比率的总弧气流量形成了最好的涂层。文中还讨论了在惰性气氛（如He）中,热循环对陶瓷试样的影响。结果表明,涂层没有衷变。为了证明使用涂层保护石墨免遭氧化是可行的,用真空等离子喷涂陶瓷涂层于石墨上。     

等离子喷涂耐蚀涂层在罗茨风机修复上的应用

大型化工企业的关键设备罗茨风机，在长期工作后因腐蚀而降低生产效率，本文就用等离子喷涂技术对其修复进行试验探讨，重点介绍了涂层材料选择，工艺试验，工装准备及喷涂过程，得出了修复后使用效果良好的结论。     

钼基合金涂层及其应用

通常就金属表面处理所获得的复层来说,可以分为三类:表面转化复层、转移镀层和沉积涂层。所谓沉积涂层,就是采用热喷涂方法将预先选择的涂层材料加热熔融后以高速喷射到基材表面,使之产生强烈变形而堆积形成涂层的一种工艺方法。形成的涂层与基材间除机械式啮合外,由于颗粒以高温、高速对基材的瞬时作用,还有着冶金相的熔合和物理粘结。除纯钼涂层外,它还包括钼基合金、铬基合金、陶瓷及金属陶瓷涂层等等。获得的涂层以提高初期磨合性和耐磨损、耐腐蚀等为主要目的。 按热源形式分类,该工艺方法主要有火焰喷涂、电弧喷涂和等离子体喷涂。火焰喷     

活塞环表面等离子喷涂强化及耐磨性能的研究

采用等离子喷涂技术,在活塞环表面喷涂一层Mo+28%NiCrBSi复合材料,并对复合材料涂层的金相组织、硬度、抗咬死和耐磨性进行了实验研究。结果表明采用等离子喷涂工艺制备的Mo+28%NiCrBSi复合材料涂层具有良好抗咬死性及耐磨性,是目前理想的活塞环涂层。     

陆用燃气轮机HVOF喷涂层的经济效益

ＭＣｒＡｌＹ涂层广泛应用于改善陆用燃气轮机叶片和叶片的抗高温、耐热腐蚀性能。此外,使用诸如ＩＮ７３８ＬＣ或ＩＮ９３９之类的Ｎｉ基超合金进行表面修复,对于重新装配的叶轮和叶片来说,在某些情况下是必须的。过去,这类涂层绝大多数是用真空等离子喷涂（ＶＰＳ）或低压等离子喷涂（ＬＰＰＳ）来制备的,而在最近几年,这类涂层对高速氧燃料喷涂（ＨＶＯＦ）的兴趣在不断增加,这是因为对薄涂层和小零件来说,由于工艺简单而使这种方法具有较低的成本,并且由于较高的粒子速度和较低的火焰温度使其涂层质量可以与ＶＰＳ喷涂的优质涂层相比。本文首先给出了应用ＨＶＯＦ喷涂作为叶片和叶轮表面修复涂层的结果,并与ＶＰＳ涂层进行了包括成本核算、弯曲试验、热冲击试验、金相和氧分析等的质量比较。     

Comparison of solid oxide fuel cell anode coatings prepared from different feedstock powders by atmospheric plasma spray method

Atmospheric plasma spray (APS) deposition of a high-performance anode coating, which is essential for obtaining high power density from a solid oxide fuel cell (SOFC), is developed. A conventional, micron-sized, nickel-coated graphite – yttria stabilized zirconia (YSZ) – graphite blend feedstock leads to a non-uniform layered coating microstructure due to the difference in the physical and thermo-physical properties of the components. In this research, new types of feedstock material received from a spray-drying method, which includes nano-components of NiO and YSZ (300 nm), are used. The microstructure and mechanical properties of a coating containing a nano composite that is prepared from spray-dried powders are evaluated and compared with those of a coating prepared from blended powder feedstock. The coating microstructures are characterized for uniformity, mechanical properties and electrical conductivity. The coatings prepared from spray-dried powders are better as they provide larger three-phase boundaries for hydrogen oxidation and are expected to have lower polarization losses in SOFC anode applications than those of coatings prepared from blended feedstock.     

Low temperature assisted chemical coprecipitation synthesis of 8YSZ plasma sprayable powder for solid oxide fuel cells

Plasma spraying is one of the potential manufacturing technologies widely used in tubular solid oxide fuel cells (SOFC) fabrication. The plasma spray technology requires powders with good flowability and large particle size (5-200 μm). A simple, low temperature assisted chemical process was used for the preparation of plasma grade yttria stabilized zirconia powder without any agglomeration process. The powder was characterized by X-ray diffractometry, particle size analysis, scanning electron microscopy and Raman spectroscopy. The powder exhibited cubic phase, good flowability and blocky angular shape. The 8YSZ powder was plasma sprayed and the coatings after sintering showed gas tightness (gas leak rate ∼ 1 × 10⁻⁶ mbar l s⁻¹ cm²). This was substantiated by the presence of densely packed grains as seen in the surface FESEM image of the sintered plasma sprayed 8YSZ free form. Conductivity values in par with the values reported in literature were obtained for plasma sprayed 8YSZ coating.     

Effect of addition method of gadolinia-doped ceria-added FeCr gas diffusion layer on performance of direct-methane solid oxide fuel cells

A solid oxide fuel cell (SOFC) was set up with a porous disk of gadolinia-doped ceria (GDC)-added FeCr as a gas diffusion layer under direct-methane feeding. The addition of GDC was done by mixing GDC powder with FeCr powder before disk fabrication, or by coating GDC powder or impregnating GDC precursor to the surface of the porous FeCr disk. When GDC was added by mixing, the direct-methane SOFC (DM-SOFC) performance degraded very rapidly. When GDC was added by either powder coating or impregnating, the DM-SOFC performance can be relatively stable. Both the current density and the CO₂ selectivity with GDC addition by impregnating are larger than those by powder coating.     

LiFePO4/carbon cathode materials prepared by ultrasonic spray pyrolysis

Small crystallites LiFePO₄ powder with conducting carbon coating can be synthesized by ultrasonic spray pyrolysis. Cheaper trivalent iron ion is used as the precursor. The pure olivine phase can be prepared with the duplex process of spray pyrolysis (synthesized at 450, 550 or 650 °C) and subsequent heat-treatment (at 650 °C for 4 h). The results indicate that the pyrolysis temperature of 450 °C is appropriate for best results. The carbon coating on the LiFePO₄ surface is critical to the electrochemical performance of LiFePO₄ cathode materials of the lithium secondary battery, since the carbon coating does not only increase the electronic conductivity via carbon on the surface of particles, but also enhance the ion mobility of lithium ion due to prohibiting the grain growth during post-heat-treatment. The carbon of 15 wt.% evenly distributed on the final LiFePO₄ powders can get the highest initial discharge capacity of 150 mA h g⁻¹ at C/10 and 50 °C.     

Reduction of radiative heat transfer in thermal insulations by use of dielectric coated fibers

This paper reports an analysis on using coated silica fibers to reduce radiative heat transfer through thermal insulations. Considerations were given to silica fibers of diameters 2, 5, and 10 μm. They were coated with either a 0.2 μm silicon coating or a 0.2 μm silicon inner coating and a 0.1 μm silica outer coating. Calculations were performed to determine the ratio of radiative heat flux for coated fibers to that for uncoated fibers. The calculations were made for both constant fiber number density and constant bulk density. It was found that keeping the fiber number density constant resulted in larger reductions in radiative heat flow. For the test conditions examined, reduction as high as 75 percent was shown to be possible.     

Heat, mass and momentum transfer in coating formation by plasma spraying

The plasma jets produced by d.c. spray torches exhibit unusual properties: high flow velocities (up to 2 500 m · s ⁻¹ ), high temperatures (up to 14 000 K), steep temperature and velocity radial gradients (up to 10 ⁷ K · m ⁻¹ and 5.10 ⁵ s ⁻¹ ) and low gas density ( 1/30 to 1/50 that of the cold gas). They are laminar in their core and turbulent in their fringes. When they exit the torch nozzle, the resulting vortices coalesce inducing an engulfment process of the ambient gas with large scale eddies entraining bubbles of cold gas. The latter do not mix instantaneously with the plasma due to the high density difference. Mixing occurs after the heating of the cold inclusions. In addition, the plasma jets are continuously fluctuating in length and position because of the continuous movement of the arc root on the anode wall at frequencies ranging between 3 and 20 kHz. This results in a sort of piston flow. In plasma spraying, the solid particles are injected in the plasma jet through an injector set downstream or upstream of the nozzle exit. In this injector, particles collide between themselves and the injector wall. Therefore, they have trajectory and velocity distributions at the injector exit. It results in a dispersion of their trajectories within the jet. The flow rate of the powder carrier gas has to be adjusted to give the particles about the same momentum as that of the plasma jet at the injection point. The large difference between particle and flow velocity can induce convective movements within the molten droplets resulting in a continuous renewing of the liquid material at the particle surface. For metal or alloy particles sprayed in air this internal movement brings about a high oxidation rate enhanced by the presence of atomic oxygen in the jet. Particles impact on the part to be covered at velocities between 150 and 300 m · s ⁻¹ . The liquid material spreads out from the point of impact and forms a lamella called “splat”. The flattening time is below a few μ s and splat solidification generally starts before the flattening process is completed. The next particle that impacts a few tens of μ s later, flattens on already solidified particles. The piling up of a few splats forms a pass in less than one millisecond, then, the next pass is deposited a few seconds later. The thickness of a pass varies between 3 and 60 μ m. The flow and heat phenomena during the impact and solidification processes control the microstructure and thermo-mechanical properties of coatings. The build-up of a coating in plasma spraying is a multiscale problem with time scales ranging between microseconds and seconds and length scales ranging between a few micrometers and a few hundred micrometers or more. Therefore, models and experiments deal with either the formation of splats or the piling of layers. This paper will review what is our present knowledge of the modeling and measurement of the transient phenomena involved in the various subsystems of the plasma spray process: jet formation, particle injection, particle heating and acceleration and coating formation.     

粉末火焰喷涂法制备黑铬太阳能选择性吸收涂层的实验研究

采用粉末火焰喷涂法制备的黑铬太阳能选择性吸收涂层,工艺简单,成本低,性能稳定,光谱选择性好。其可见光谱区的吸收率为０．９１,红外光谱区的发射率为０．１５。对黑铬涂层和黑板漆作集热板的太阳热水器性能进行了实验比较和讨论。     

Hydrogenated amorphous silicon films deposited at high growth rates by the cathode heating technique: properties and light induced degradation

The deposition of hydrogenated amorphous silicon (a-Si:H) films at high growth rates (≈ 10 Å/s) by plasma enhanced chemical vapour deposition, showing acceptable optoelectronic properties, was achieved by impeding powder growth in the plasma through heating of the cathode and hydrogen dilution of the source gas silane. In view of the high rf power densities used for film growth, the properties of the films in the surface and near surface regions were studied together with that of the bulk. Light induced degradation of the samples deposited under conditions where powder growth in the plasma was suppressed as well as conditions of dusty plasma were studied. Changes in the generation efficiency × mobility × lifetime product and the defect density were monitored with light soaking time.     

Study of Thermal Conductivity and Geometry Wall Contact Resistance Effect of Granular Active Carbon for Refrigeration and Heat Pumping Systems

The commercial success of sorption refrigeration and heat pump systems depends on a good heat and mass transfer in the adsorbent bed, which allows higher coefficients of performance and greater specific heating or cooling power that reduce capital costs. In this study the thermal conductivity and thermal contact resistance of vibrated and compressed granular active carbon and binary mixtures of active carbon are investigated using two types of conductivity measurements: a steady-state measurement between flat plates and a transient hot tube measurement. With these results is possible to draw conclusions on how the wall geometry, particle size distribution, and bulk density affect the overall thermal performance. Results show that using binary mixtures of grains and powder gives results superior to those of either grains or powder alone. The conductivity of the binary mixtures increases roughly linearly with bulk density and the 2/3 grain mixture achieves the highest densities. The method used to achieve compaction (vibration or compression) did not seem to affect the result. Thermal contact resistances reduce with increasing density but do vary with the mixture ratio, also appearing to be best with a 2/3 grain–1/3 powder mixture.     

Evaluation of Ni80Cr20/(La0.75Sr0.25)0.95MnO3 dual layer coating on SUS 430 stainless steel used as metallic interconnect for solid oxide fuel cells

Ni₈₀Cr₂₀/(La_0.75Sr_0.25)_0.95MnO₃ dual-layer coating is deposited on SUS 430 alloy by plasma spray for solid oxide fuel cell (SOFC) interconnect application. The phase structure, area specific resistance (ASR), and morphology of the coating are studied. A two-cell stack is also assembled and tested to evaluate coating performance in an actual SOFC stack. The NiCr/LSM coating adheres well to the SUS 430 alloy after oxidation in air at 800 °C for 2800 h. The ASR and its increasing rate of coated alloy are 25 mΩ cm² and 0.0017 mΩ cm²/h, respectively. In an actual stack test, the maximum output power density of the stack repeating unit increases from 0.32 W cm⁻² to 0.45 W cm⁻² because of the application of NiCr/LSM coating. The degradation rate of the stack repeating unit with no coating is 4.4%/100 h at a current density of 0.36 A cm⁻², whereas the stack repeating unit with NiCr/LSM coating exhibits no degradation. Ni₈₀Cr₂₀/(La_0.75Sr_0.25)_0.95MnO₃ dual-layer coating can remarkably improve the thermal stability and electrical performance of metallic interconnects for SOFCs.