盐雾试验中各试验参数对结果的影响

以采用ISO 3574:2012的CR4级冷轧碳钢板为腐蚀对象,进行大量试验,探究GB/T2423.17-2008盐雾腐蚀试验中各参数对试验结果的影响。同时定义一种指数,评价相关参数的影响程度。试验结果表明,喷嘴压力和热水塔温度对盐雾试验结果的影响较大。研究成果为优化盐雾试验的参数控制提供了指引方向。     

Plasma spray coating processes

Abstract

Plasma spray deposition is one of the most important technologies available for producing the high–performance surfaces required by modern industry. Over the past 25 years, there have been significant advances in the understanding of plasma physics and in the development of spraying equipment and techniques. This has enabled a range of materials including metals, alloys, ceramics, and cermets to be plasma sprayed on to a great variety of substrate types and geometries. During this period, the uniquely aggressive environment within the gas turbine engine has provided not only some of the greatest challenges to plasma spraying technology, but also some of its most successful applications. In this paper, the nature of plasma and plasma spray devices are discussed and factors affecting coating quality are considered. Practical aspects of plasma spraying are considered and finally the application of plasma spray coating processes to the protection of high–temperature gas turbine components is discussed using as examples turbine blade overlay coating, coatings for hot gas path seals, and ceramic thermal barrier systems.

MST/282     

A wear-resistant coating—Oxidized graded multilayer TiN/W coating

Combining sputtering technology using an industrial-scale four-target DC closed-field unbalanced magnetron sputtering ion plating system (CFUBMSIPS™) with post heat treatment, a graded multilayer TiN/W coating, consisting of five layers, was synthesized and its outmost W layer was transformed to lubricious WO₃ successfully. The coatings were characterized by using GDOES, GXRD, a Rockwell C indentation tester, a nanoindentation tester, and a scratching tester. Wear behavior of coatings was evaluated by using a pin-on-disc tribometer. Through proper post heat treatment, the multilayer TiN/W coating, in spite of having a lower nano-hardness, showed good adhesion, much better wear performance and lower friction coefficient compared with the reference monolayer TiN coating.     

加载参数对TiN涂层摩擦磨损行为的影响

TiN薄膜广泛应用于低速轴承、钟表齿轮等环境中,而微载、低速条件下TiN薄膜的摩擦学特性是其重要服役性能之一.采用球盘式干滑动摩擦磨损试验机,研究了多弧离子镀TiN薄膜在微载、低速条件下的摩擦磨损特性.研究表明:在本试验范围内,薄膜的摩擦系数随着载荷的增加而升高,磨盘转速和转动半径对摩擦系数基本没有影响;载荷、磨盘转速的升高缩短了材料的磨合时间,而转动半径的增加延长了磨合距离.磨损以对磨钢球的犁削磨损为主,磨损体积随转动半径的增加而增加.     

Interfacial mechanical properties of TiN coating on steels by indentation

The elastic theory of indentation on nitride films/steel systems showed distribution of stresses (shear stress, radial stress and circumferential stress) near the interface and in the film. The difference in values for each stress along the distance to the load center increased with increasing Poisson’s ratios of steels. The shear stresses (σ_rz) had the maximum value at a distance to the load center and the difference became more significant with increasing Poisson’s ratios of steel substrates (from 0.2–0.3 of Poisson’s ratio for high-speed steels to 0.3–0.35 for stainless steels), which accounted for the large amount of cracks inside the indent cavity of nitride films/stainless steel in spite of the smoothness outside the cavity. The calculation of σ_r and σ_z showed that the differences in nitride films/steel stress increased with increasing Poisson’s ratios of steels, which also facilitated the formation of ring cracks in the film of nitride films/stainless steel composite. Indentation examination revealed the large amount of cracks inside the indent cavity of nitride film/stainless steel but smooth surface outside the cavity. These were formed under the high sinusoidal shear stress and circumferential radial stress due to the higher Poisson’s ratio of stainless steel and the plastic deformation due to the lower yield stress of stainless steel (SS), which induced more local residual stresses, whereas some cracks or spalling observed around the cavity and no cracks inside the cavity were attributed to the edge effect when the conical indenter strained the surface downward for nitride film/high-speed steel (HSS) system.     

Morphology of TiN coating produced by laser ablation

The morphology of TiN thin films on a steel surface produced by the process of laser ablation has been investigated. The process involves material removal from a titanium target by means of an ultraviolet excimer pulse laser. Both the target and the steel substrate are in an ammonia atmosphere and therefore the titanium atoms react with the nitrogen under the influence of a laser-induced plasma, and the product, which is TiN, is deposited on the surface of the steel. The investigation revealed that at the beginning of the process the TiN film is uniform; however, with increasing number of pulses, small micrometre-sized particles begin to appear on the surface and after a large number of pulses all the surface is covered with these particles.     

Future developments in plasma spray coating

Abstract

Future coating developments for high–temperature gas turbine components is a topic which encompasses both material and process developments. The materials for use at high temperatures can be classified as wear (abradables and abrasives), corrosion, oxidation, and thermal barrier coatings. In spite of many interesting material modifications, the most important developments are associated with the application process, coating quality control procedures, and efficiency of operation regarding the source of material used to produce the coating.

MST/295     

吸热陶瓷涂层的火焰喷涂及其耐磨行为

对在钢材表面采用的氧乙炔火焰喷涂这一新型吸热陶瓷材料的耐磨性能及耐磨机理进行了试验研究结果表明，该涂层具有较低的孔隙率、较高的硬度和抗压强度，以及良好的耐磨性。其磨损机理主要有塑性涂抹、磨粒磨损和疲劳剥落。     

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.     

A superhydrophobic polyacrylate film with good durability fabricated via spray coating

A superhydrophobic film with good durability was fabricated by simple spraying a mixed solution of a POSS-based fluorinated acrylate polymer and ethyl-α-cyanoacrylate on a glass slide. The polymer was firstly synthesized via a typical free radical solution polymerization and could self-assemble into spherical micelle, thus leading to the formation of a rough film with hierarchical nano-microstructure through spray coating. The adding of ethyl-α-cyanoacrylate can improve the mechanical durability of the film. The film shows robust superhydrophobicity with a high water angle contact of 158° and an ultralow water sliding angle of 1.9°. More importantly, the film not only can withstand 25 abrasion cycles under a load of 200 g and approximately 5.5 m high static water pressure without losing superhydrophobicity, but also exhibits favorable resistance to acidic and basic solutions over a wide range of pH values from 2 to 14. Besides, the transmittance of the coated glass slide is above 75% in the visible light range of 400–800 nm, reflecting high transparency of the film. This film may be a promising candidate in practical applications, including coating of optical devices, solar cell panel and outdoor instruments, because this method to fabricate supehydrophobic surfaces is facile, effective and scalable, and the superhydrophobic coating has good water resistance, high transparency and enough durability.     

真空管道TiN膜热出气率实验研究

简要叙述了小孔流量法测量材料出气率实验的原理和实验装置，给出了不锈钢溅射镀TiN膜在不同情况下的热出气率，并对影响不锈钢溅射镀TiN膜热出气率情况的各种因素进行了分析，为使用溅射镀TiN膜表面处理的储存环真空室的设计提供了依据。     

碳化硅环氧树脂涂料喷涂工艺研究

研究获得了一种溶剂型高固体含量的碳化硅环氧树脂涂料工艺配方,并总结了喷涂过程常见问题及其解决方法;重点分析了几种分散剂和活性稀释剂对涂料黏度的影响,及分散剂对涂料中碳化硅分散性的影响.结果表明,分散剂能改善涂料的粘度及碳化硅的分散性,含量20%活性稀释剂能显著地降低涂料黏度;力学性能测试表明,涂层附着力1级,弯曲强度2mm无破坏.     

Formation by reactive magnetron sputtering of TiN coating on Ti-implanted magnesium alloy

Reactive magnetron sputtering method was used to deposit TiN coating on Ti-implanted magnesium alloy. FESEM, GIXRD and AES were used to investigate this surface system's micro-morphology, crystalline structure and chemical composition, respectively. It showed that TiN coating took on a compact surface morphology and existed as a columnar crystalline structure. The results of the electrochemical test and immersion test showed that the corrosion resistance of AZ31 was greatly improved in 3.5 wt.% NaCl solution by this kind of surface treatment technique. It was mainly due to the combined effect of the dense TiN coating, the Ti-implanted layer and the good adhesion between coating and substrate.     

Effect of parameters on adhesion strength for slurry spray coating technique

In this article, slurry spray technique (SST) has been adopted for depositing mullite–nickel based environmental barrier coatings (EBCs) on some ASTM 1018 low-carbon steel. Considerable value of adhesion strength of a deposited cermet is critical for the coating to comply with service condition. The effect of identified process parameters like stamping pressure, fly ash content, sintering additive, sintering time, and sintering temperature on optimizing adhesion strength is evaluated. Parametric assessment of the developed coatings is done utilizing Taguchi L₁₈ orthogonal array and analysis of variance (ANOVA). Based on the analytical study of the experimentation, the dependence of adhesion strength of slurry sprayed coatings on the process parameters has been studied. Maximum adhesion strength value of 18.15?MPa was attained during experimentation within the range of the selected control parameters. The enhanced adhesion strength was found for increased sintering temperature up to 950°C which may be attributed to the improved sintering of mullite mixed fly ash due to lowering of secondary mullitization temperature. Furthermore, it has been proven experimentally that the quality of coatings achieved in this work is acceptable and approaching to the quality of thermal coatings manufactured with commercially available fabrication methods.     

Effect of gravity on pool boiling heat transfer on thermal spray coating

This study deals with heat transfer enhancement surface manufactured by thermal spraying. Two thermal spraying methods using copper as a coating material, wire flame spraying (WFS) and vacuum plasma spraying (VPS), were applied to the outside of copper cylinder with 20 mm OD. The surface structure by WFS was denser than that by VPS. The effect of gravity on boiling heat transfer coeffcient and wall superheat at the onset of boiling were experimentally evaluated under micro- and hyper-gravity condition during a parabolic trajectory flight of an airplane. Pool boiling experiments in saturated liquid of HCFC123 were carried out for heat fluxes between 1.0 and 160 kW/m² and saturated temperature of 30 °C. As a result, the surface by VPS produced higher heat transfer coefficient and lower superheat at the onset of boiling under microgravity. For the smooth surface, the effect of gravity on boiling heat transfer coefficient was a little. For the coating, a large difference in heat transfer coefficient to gravity was observed in the moderate heat flux range. The heat transfer coefficinet decreased as gravity changed from the normal to hypergravity, and was improved as gravity changed from the hyperto microgravity. The difference in heat transfer coefficient between the normal and microgravity was a little. Heat transfer enhancement factor was kept over the experimental range of heat flux. It can be said that boiling behavior on thermal spray coating might be influenced by flow convection velocity.     

GSV测试技术在喷雾场试验上的应用

喷雾流场的特性对航空发动机火焰筒燃烧质量有着重要的影响,优化喷嘴雾化性能可以提高燃烧质量。而研究流场特性和优化雾化喷嘴性能的前提是对流场内液滴尺寸与速度以及其分布进行准确有效的测量和表征。介绍全场粒径流速测量系统(global sizing velocity,GSV)测试技术,并应用该技术对喷雾场中部分区域的液滴尺寸和速度进行测量。基于对测量数据的分析,检测喷嘴的雾化性能,同时测试结果表明:GSV技术在喷雾场区域的粒径测量方面有较好的应用性,在速度测量方面仍有待改进。     

Transmission electron microscopy analysis of a TiN x substoichiometric CVD coating

The TiN _{x 1–x} substoichiometric chemical vapour deposited titanium nitride coatings have been studied in an early work by means of high-resolution X-ray emission spectroscopy. It was found that a strong vacancy-induced peak was present in the Ti K emission band. Its intensity can be correlated to the 1–x vacancy concentration deduced from nuclear reaction spectroscopy and X-ray diffraction. This relationship is linear if 01–x0.3. If 1–x is higher than 0.3, an anomalous behaviour occurs which is expected to be due to microstructure change. For this purpose, transmission electronic studies of a TiN_{0.57 0.43} layer have been developed. The most striking result of this work is the existence of many stacking faults. These defects are extrinsic ones and the stacking fault energy is about 3.5 mJ m^–2. Their density seems to depend on their distance from the substrate-coating interface. Further investigations are needed to confirm this assumption.     

Shell porosity in spray fluidized bed coating with suspensions

An experimental study regarding spray fluidized bed coating with aqueous suspensions is presented. The dependency of coating shell morphology on drying parameters, atomization pressure and composition of suspension is investigated. The results are compared to existing work regarding spray fluidized bed coating with aqueous solutions of crystalline material. Contrary to coating with solutions, coating shell smoothness and porosity does not depend on drying conditions. Nevertheless, atomizing pressure and mass fraction of solids in suspension have large influence on coating shell morphology. High atomization pressures, leading to small droplets, result in smooth coating surfaces and low shell porosities. A similar trend is observed for a low mass fraction of solids in the suspension.     

Microstructure, chemistry and coating properties of ion-plated TiN on type 304 stainless steel

Characterization of TiN coatings on type 304 stainless steel was carried out using a Zeiss EM 902A energy filtering transmission electron microscope equipped with an electron energy loss spectroscopy (EELS) detector. TiN thin films were produced by a hollow cathode discharge ion plating coater. It was found by plan-view transmission electron microscopy that the microstructure of the TiN coatings is thickness dependent. The grain size of TiN ranges from 88 nm at the coating surface down to 9 nm near the TiN/steel interface. In addition, the TiN surface layer shows some degree of texture, but the subsurface and internal TiN layers are mainly equiaxial and randomly oriented. Chemical analysis by EELS shows that the relative oxygen content increases linearly from the TiN surface to the TiN/steel interface, whereas the relative nitrogen content first decreases slowly and then drops rapidly near the interface. The presence of a Ti₂N phase and the deficiency of nitrogen near the TiN/steel interface suggest that the early-deposited TiN is nonstoichiometric. By the periodic cracking method, the ultimate shear stress at the TiN/steel interface and the residual stress in the TiN thin film were estimated to be 2.2 GPa and 12.8 GPa, respectively.