等离子喷涂陶瓷螺杆的软仿型工艺的研究

提出以软仿型加工方法实现陶瓷螺杆等离子喷涂,该方法以螺杆螺距为仿型参数,实现数控位移,以软仿型方式实现螺杆表面喷涂.探讨了该方法的工艺原理和实现技术途径,研究结果表明采用该方法有助于提高陶瓷螺杆的喷涂效率.     

Laser-assisted spraying and laser treatment of thermally sprayed coatings

In the present study, surface engineering research related to thermally sprayed wear and corrosion resistant coatings modified by in-situ and post-treatment by novel high power lasers (Nd:YAG and diode lasers) has been carried out. The main aim of the study was to create experimental based information and knowledge on simultaneous remelting of thermally sprayed (plasma, HVOF, flame) single layers for production of metallurgically bonded, dense corrosion and wear resistant coatings on surfaces of steels. The main focus of research was to estimate the needed processing parameters, which enable simultaneous laser-assisted thermal spraying. The microstructures and hardness-profiles for the coatings prepared by laser-assisted thermal spraying are also introduced.     

Growth mechanism and corrosion behavior of ceramic coatings on aluminum produced by autocontrol AC pulse PEO

Ceramic coatings are produced on aluminum alloy by autocontrol AC pulse Plasma Electrolytic Oxidation (PEO) with stabilized average current. Transient signal gathering system is used to study the current, voltage, and the transient wave during the PEO process. SEM, OM, XRD and EDS are used to study the coatings evolution of morphologies, composition and structure. TEM is used to study the micro profile of the outer looser layer and inner compact layer. Polarization test is used to study the corrosion property of PEO coatings in NaCl solution. According to the test results, AC pulse PEO process can be divided into four stages with different aspects of discharge phenomena, voltage and current. The growth mechanism of AC PEO coating is characterized as anodic reaction and discharge sintering effect. PEO coating can increase the corrosion resistance of aluminum alloy by one order or two; however, too long process time is not necessarily needed to increase the corrosion resistance. In condition of this paper, PEO coating at 60 min is the most protective coating for aluminum alloy substrate.     

等离子喷涂纳米结构AT13基涂层工艺图的建立

利用定量金相分析、显微硬度测试、压痕断裂试验、结合强度测试和摩擦磨损试验,通过正交设计试验对等离子喷涂纳米结构Al2O3-13%TiO2(AT13)基陶瓷涂层的工艺进行了优化.分析了工艺参数、微观结构、力学性能之间的关系,提出了喷涂工艺图的建立方法,建立了相应的三维关系图.通过该工艺图可确定各个性能最优的工艺参数范围.     

等离子喷涂Al2O3与Cr2O3涂层性能的研究

对等离子喷涂Ａｌ２Ｏ３、Ｃｒ２Ｏ３涂层耐蚀性和耐磨性的试验研究表明,在３．５％ＮａＣｌ介质中,Ａｌ２Ｏ３涂层耐蚀性优于Ｃｒ２Ｏ３涂层;在滑动磨损条件下,Ｃｒ２Ｏ３涂层的耐磨性优于Ａｌ２Ｏ３涂层。     

热障涂层的CMAS腐蚀失效及对策研究综述

研制具有长寿命、高性能的热障涂层（TBCs）,是制造我国大功率航空发动机、发展新一代超音速战机的一项十分紧迫的任务。由于外来沉积物CaO-MgO-Al2O3-SiO2（CMAS）渗入涂层而导致TBCs失效的现象越来越受到人们的重视,在过去的一段时间里,很多学者对CMAS渗入后涂层的失效机理进行了大量的研究并尝试了一些缓解CMAS渗入涂层的方法。本文针对当前应用最为广泛的“层状多孔结构”的等离子喷涂涂层及“细长柱晶结构”的电子束辅助物理气相沉积涂层,系统地梳理了近年来国内外学者对TBCs在CMAS渗入条件下的失效机制及涂层缓解CMAS渗入方面的最新研究成果,为制备高性能的TBCs提供帮助。     

Ceramic/fluoropolymer composite coatings by plasma spraying

Al₂O₃-TiO₂/perfluorinated vinylether (PFA) composite coatings are produced by plasma spraying. Because of the different thermo-physical characteristics of both materials, two systems of powder injection were studied: injection of mixed powders and separated injection (co-injection). The effect of the powder injection on the coating microstructure and on the PFA content was investigated using different methods, i.e., micrographic examination, image analysis and energy-dispersive spectrometry (EDS). From micrographic examination, it was observed that a composite structure can be obtained whatever the considered injection system. The coatings consist of a ceramic matrix in which rounded PFA particles are dispersed homogeneously. The content values of the polymer within the coatings evaluated by image analysis show a PFA increase. This trend is not observed for coatings realized by co-injection. On the other hand, powder injection system has no influence on the content of the polymer located at the coating surface. EDS analyses carried out for fluor and aluminium elements prove that PFA particles are homogeneously dispersed at the coating surface. The use of an appropriated thermal post-treatment allows polymer melting and its spreading.     

Characterisation of corrosion and wear behaviour of nanoscaled e-beam PVD CrN coatings

The present paper analyses the performance of CrN single-layers produced by electron beam PAPVD (EBPAPVD), finding that both corrosion and wear resistance are directly dependant on the structure and stoichiometry of the nitride. The nanolayer structure of the coatings is formed by periodically varying the nitrogen pressure during deposition resulting in layers with higher and lower N-content. This fact, which has not been described in the literature, causes different structure and morphology of the individual films providing excellent properties to the coating. For corrosion resistance, the CrN layer's greater compactness impedes penetration of the electrolyte and thus prevents the formation of a galvanic couple between the coating and the substrate. Moreover, a good wear resistance is obtained, retarding its delamination.     

ZrO2陶瓷热障涂层的研究

用等离子涂技术制备了ＺｒＯ２结构梯度和成份梯度涂层,并试验测定了各涂层的隔热效果及抗热震性,涂层试片在２．５Ｍａ、１８００℃、５８００ＫＷ／ｍ＾２的热流冲刷５ｓ后,结果表明：涂层表面仍较光滑,与烧蚀前无明显差别,更无剥落,崩裂出更,平均每毫米隔热涂层降温约４０２．２℃。     

Abrasive wear behaviour of laser clad and flame sprayed-melted NiCrBSi coatings

In this work, the influence of the processing conditions on the microstructure and abrasive wear behaviour of a NiCrBSi hardfacing alloy is analysed. The hardfacing alloy was applied in the form of coatings onto a mild steel substrate (Fe–0.15%C) by different techniques: laser cladding (LC) and flame spraying (FS) combined with surface flame melting (SFM). In both cases, the appropriate selection of the process parameters enabled high-quality, defect-free NiCrBSi coatings to be obtained. The microstructure of the coatings was analysed by scanning electron microscopy (SEM), with attached energy dispersive spectroscopy (EDS) microprobe, and by X-ray diffraction (XRD). Their tribological properties were evaluated by micro-scale ball cratering abrasive wear tests using different abrasives: diamond, SiC and WC. Microstructural characterisation showed that both coatings exhibit similar phases in their microstructure, but the phases present differ in morphology, size distribution and relative proportions from one coating to another. Wear tests showed that in three-body abrasive conditions, despite these microstructural differences, the wear behaviour is comparable for both coatings. Conversely, in two-body wear conditions with diamond particles as the abrasive, it was observed that the specific wear rate of the material is sensitive to microstructural changes. This fact is particularly apparent in LC coatings, in which the zones of the layers with higher proportions of very small hard particles present a lower wear resistance. These results indicate that it is important to have good microstructural control of this material, in order to obtain coatings with an optimized and homogeneous tribological behaviour.     

Improvement of corrosion and wear resistances of AISI 420 martensitic stainless steel using plasma nitriding at low temperature

The influence of low temperature plasma nitriding on the wear and corrosion resistance of AISI 420 martensitic stainless steel was investigated. Plasma nitriding experiments were carried out with DC-pulsed plasma in 25% N₂ + 75% H₂ atmosphere at 350 °C, 450 °C and 550 °C for 15 h. The composition, microstructure and hardness of the nitrided samples were examined. The wear resistances of plasma nitrided samples were determined with a ball-on-disc wear tester. The corrosion behaviors of plasma nitrided AISI420 stainless steel were evaluated using anodic polarization tests and salt fog spray tests in the simulated industrial environment.The results show that plasma nitriding produces a relatively thick nitrided layer consisting of a compound layer and an adjacent nitrogen diffusion layer on the AISI 420 stainless steel surface. Plasma nitriding not only increases the surface hardness but also improves the wear resistance of the martensitic stainless steel. Furthermore, the anti-wear property of the steel nitrided at 350 °C is much more excellent than that at 550 °C. In addition, the corrosion resistance of AISI420 martensitic stainless steel is considerably improved by 350 °C low temperature plasma nitriding. The improved corrosion resistance is considered to be related to the combined effect of the solid solution of Cr and the high chemical stable phases of ?-Fe₃N and α_N formed on the martensitic stainless steel surface during 350 °C low temperature plasma nitriding. However, plasma nitriding carried out at 450 °C or 550 °C reduces the corrosion resistance of samples, because of the formation of CrN and leading to the depletion of Cr in the solid solution phase of the nitrided layer.     

Microstructure and corrosion resistance of ceramic coating on carbon steel prepared by plasma electrolytic oxidation

Ceramic coating was prepared on Q235 carbon steel by plasma electrolytic oxidation (PEO). The microstructure of the coating including phase composition, surface and cross-section morphology were studied by X-ray diffraction (XRD), Fourier transform infrared spectroscope (FTIR) and scanning electron microscopy (SEM). The corrosion behavior of the coating was evaluated in 3.5% NaCl solution through electrochemical impedance spectra (EIS), potentiodynamic polarization and open-circuit potential (OCP) techniques. The bonding strength between Q235 carbon steel substrate and the ceramic coating was also tested. The results indicated that PEO coating is a composite coating composed of FeAl₂O₄ and Fe₃O_4. The coating surface is porous and the thickness is about 100 μm. The bonding strength of the coating is about 19 MPa. The corrosion tests showed that the corrosion resistance of Q235 carbon steel could be greatly improved with FeAl₂O₄-Fe₃O₄ composite coating on its surface.     

The effect of interlayer on corrosion resistance of ceramic coating/Mg alloy substrate in simulated physiological environment

Ceramic coatings are deposited on biodegradable magnesium alloys by physical vapor deposition to reduce the electrochemical activity in the simulated physiological environment. Although an interlayer is generally used to reduce the mismatch between the hard coating and soft substrate, the effects of the interlayer on the electrochemical corrosion behavior have seldom been explored. In this work, AlO_xN_y ceramic coatings were deposited on AZ31 magnesium alloys with Al or Ti interlayers. Polarization tests and electrochemical impedance spectroscopy (EIS) were conducted to evaluate the corrosion resistance in the cell culture medium. The AlO_xN_y ceramic coating significantly improved the bio-corrosion resistance of the magnesium alloy, but the Ti interlayer accelerated the corrosion rate. In comparison, although the addition of an Al interlayer led to smaller enhancement in the surface mechanical properties of the AlO_xN_y coating, corrosion could be impeded effectively. Our results indicate that an Al interlayer is preferred over Ti and the corrosion failure mechanism is discussed from the perspective of defects.     

陶瓷相增强铁基耐磨堆焊层组织与性能的研究

为了将铁基良好的韧性和陶瓷的高硬度、高耐磨性、高耐腐蚀性结合在一起,制备出性能更为良好的堆焊层,自行调整合金粉末的合金体系,在铁基的基础上涂覆一层由钛铁、硼铁、硅铁、镍粉以及高碳铬铁等组成的合金粉末,采用乒极性等离子弧堆焊技术,调节焊接工艺及参数,通过焊接冶金反应,使其原位自生形成陶瓷硬质相。通过硬度、磨损、微观组织分析可知：堆焊层的性质得到了很大的改善,洛氏硬度达58以上,且耐磨性很好,与直接加入硬质相相比大大节省了成本。     

Structure and Properties Characterization of Ceramic Coatings Produced on Steel Using a Combined Technique

STEEL is the most widely used material in engineering,but unfortunately,steel exhibits poor wear resistanceand obvious contact corrosion.For decades,researchersprepared coatings on steel to improve its properties;ceramic is one of these coatings.To obtain ceramiccoatings on steel,many researchers use techniques suchas plasma spraying,laser cladding,etc.,but some ofthem are too expensive,some of them have a deep heataffected zone in the substrate,and some of them cannot bond well with the subs…     

The nanostructure, wear and corrosion performance of arc-evaporated CrBxNy nanocomposite coatings

The composition, nanostructure, tribological and corrosion behaviour of reactive arc evaporated CrB_xN_y coatings have been studied and compared to CrN. The CrB_xN_y coatings were deposited on a commercial Oerlikon Balzers RCS coating system employing 80:20 Cr:B targets. To vary the composition, the nitrogen fraction was adjusted (N₂ fraction = N₂/(Ar + N₂)) and a moderate bias voltage of − 20 V was applied during coating growth. The coating composition and nanostructure was determined using time-of-flight elastic recoil detection analysis (TOF-ERDA), x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS). Ball-on-disc dry sliding wear tests were conducted using an alumina ball counterface both at room temperature and at 500 °C with the relative humidity controlled at 20%. Potentiodynamic corrosion tests were undertaken in 3.5% NaCl aqueous solution. The wear tracks were examined using optical profilometry and scanning electron microscopy (SEM); the surface composition inside and outside of the wear tracks were investigated using Raman spectroscopy and XPS. All coatings exhibit nanocomposite structures and phase compositions which are in fair agreement with those expected from the equilibrium phase diagram. The lowest wear rate at room temperature and 500 °C was found for CrB_0.14N_1.14, which was shown to exhibit the highest hardness and possesses a nanocomposite nc-CrN/a-BN structure. CrB_0.12N_0.84 coatings showed the lowest passive current density in potentiodynamic corrosion tests.     

Corrosion and wear behavior of thermally sprayed nano ceramic coatings on commercially pure Titanium and Ti–13Nb–13Zr substrates

Surface treatments and coatings are the practical approaches used to extend the lifetime of components and structures especially when the surface is the most solicited part of the considered engineering component. Hard thermally sprayed coating is one of the most wear resistance coating widely used in many practical mechanical applications. In the construction of articulating parts of medical devices, titanium and its alloys have to be surface coated to improve their tribocorrosion behavior. In this way, the use of porous thermal coatings is known to be a strategy for better binding bone or tissue on femoral stem for example. It is, thus, important to evaluate the corrosion and the wear behaviors of such materials for biosecurity considerations in the human body. In this study, we investigate the behavior of new nano ZrO₂ and Al₂O₃-13 wt.% TiO₂ thermal sprayed coatings on commercially pure (cp)-Ti (grade 4) and titanium alloy substrates. Friction and wear tests against Al₂O₃ balls showed that the wear resistance of Al₂O₃-13 wt.% TiO₂ is better than that ZrO₂ coating. Both plasma sprayings have similar abrasive wear behavior; however, the average friction coefficient is higher for alumina–titania coating. Electrochemical tests, open circuit potential monitoring and potentiodynamic polarization, were performed in simulated body conditions (Hank’s solution, 37 °C). Results showed that corrosion resistance was appreciably higher for alumina–titania coating.