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…     

Adhesive interlayers' effect on the entire structure strength of glass molding tools' Pt–Ir coatings by nano-tests determined

Precision glass molding is a technology for the medium to large scale production of complex optical components with high surface quality and form accuracy. However, the process is only economically viable if a long lifetime of the molding tools can be guaranteed. This can be achieved by using protective coatings on the optical surfaces of the molding tools. The most commonly used coatings for this application are based on noble metals, as they show reduced interaction with the glass during molding. The coatings must have excellent mechanical and chemical properties at high temperatures to withstand the stresses during molding and simultaneously extreme low surface roughness and defect density. The form accuracy of the molding tools is in the sub-μm range and must be maintained even after the coating deposition. Therefore, very thin films of approximately 300 nm thickness are used. High film adhesion and strength properties are necessary for preventing surface defects and coating delamination.In the described investigations, platinum (Pt)–iridium (Ir) coatings were deposited directly on cemented carbide samples by Physical Vapour Deposition (PVD) process. Moreover, for improving the adhesion, different materials such as of Ni and Cr were employed as adhesive interlayers at various thicknesses. These interlayers were deposited on the substrate before the Pt–Ir film, during the same PVD process. Appropriate experimental procedures were conducted for characterizing the coatings' mechanical and adhesion properties such as nanoindentations, nano-impact and nano-scratch tests. FEM calculations simulating the films' loadings during nano-impact test explain the effect of the adhesive interlayer on the entire coating substrate structure strength.     

Residual stresses in thick, nonhomogeneous coatings

Residual macrostresses in thick, nonhomogeneous planar coatings are investigated theoretically using the methods of the isotropic theory of elasticity. The dependence of the elastic properties and of the sources of residual stresses on the coordinate perpendicular to the interface is considered. The results can be applied to thick graded or sandwich coatings. A simplification of the results for the cases of homogeneous and thin coatings is shown. Some differences for coatings on cylindrical and spherical surfaces are also mentioned.     

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 在大量科学试验基础上，提出一种金属表面形成金属陶瓷的新工艺方法。该方法具有放电电压低，陶瓷层结构致密与基体冶金结合，适用于多种金属材料等优点。文中利用光学显微镜和扫描电镜（SEM）观察了陶瓷涂层的显微组织，并通过X射线衍射和机械性能试验对其相结构和室温力学性能进行了探讨。结果表明：金属陶瓷涂层的晶粒细小，分布均匀，具有高的硬度及良好的耐磨性。     

有机涂层防腐性能的研究与评价方法

综述了当前国内外常用的有机涂层防腐性能研究与评价方法，包括常规检测方法、电化学方法、表面分析技术、光谱学方法等，阐述了各种方法的特点及应用范围.不同的分析方法配合使用有助于全面、准确地评价有机涂层的耐蚀性能、研究涂层的防腐机理.     

Removal character of vertical jet polishing with eccentric rotation motion using magnetorheological fluid

The Gaussian-like removal character having its peak value in the middle is appropriate for excellent imaging quality in optical iterative manufacture. A similar removal curve of magnetorheological jet polishing was explored by using a novel polishing tool with eccentric rotation motion. As a result, the removal model with eccentric rotation motion was established based on the normal fluid impact dynamics theory, and the new-model-based removal characters with different eccentric distances were simulated. In addition, tending gene was put forward to estimate the optimal eccentric distance, with which the profile of the removal distribution approximates Gaussian character mostly. Experiments were conducted to verify the theoretical model on the K9 optical mirror with different eccentric distances using a novel setup. The polishing results indicated that the experiment value was consistent with the theoretical value. All these results have proved that the optimized model is successful and suitable for high precision polishing of complex surfaces.     

Characterization of the wear behavior of thermal sprayed coatings

Friction and wear cause a reduction in quality and properties of materials, especially their surfaces. A wear test is a good method for estimating the wear of components and their durability. This article discusses some wear test methods and results of wear tests on thermal spray composite coatings (particle-and fiber-reinforced).     

Analysis of chatter in contour grinding of optical materials

Chatter that limits ground surface finish has been observed in the deterministic microgrinding of brittle optical materials. In this article, the classical single degree of freedom model for chatter, accounting for both work and tool regenerative effects, is adapted for contour grinding optical surfaces. A linearized expression for the cutting stiffness is developed for the contour grinding geometry based on Preston’s law. Techniques developed to measure the machine frequency response function (FRF) and the Preston coefficient, needed as inputs to the simulations, are described. Numerical simulations based on this model are used to predict the grinding system behavior and to investigate process parameters affecting chatter stability. The stability limits observed during grinding experiments on optical glasses are in good agreement with the simulation results.     

The Modern Applications of Surface Duplex Treatment Technology

A TYPICAL TECHNOLOGICAL PROCESS ofduplex treatment is a combination of ion nitriding orregulated gas nitriding with PVD coating deposition bymeans of the arc-vacuum method[1].Elements,whichundergo such a duplex treatment process arecharacterised by a low friction coefficient in contactwith mating elements and low abrasive wear what istypical for elements covered with PVD coatings and atthe same time by increased resistance to highmechanical loads and increased fatigue strength,i.e.…     

Analysis of 3D microtopography in machined KDP crystal surfaces based on fractal and wavelet methods

Potassium dihydrogen phosphate (KDP) crystal surfaces machined by precise milling and single point diamond turning (SPDT) methods are analyzed in this paper. The frequency information of 3D-machined KDP crystal surfaces are decomposed and analyzed by wavelet transform method, and 3D fractal properties of different KDP crystal surfaces are calculated and analyzed by fractal method. Through the integration of fractal and wavelet analysis, it can be found that the high-frequency information of machined surfaces is incorrelate with the machining process and it can reflect the anisotropic features of material structure. The anisotropy of the machined KDP surfaces is determined by the machining process. From analysis, the strong anisotropic surfaces are easier to form microscale waveness so as to impact the optical performance of KDP crystal components severely. The result of analysis reveals that the different machining method may produce unique feature in the machined surfaces and choosing reasonable machining method may improve the microtopographic structure of machined KDP crystal surface.     

Preparation of thermal barrier coatings by ultrasonic plasma spraying

Modulated plasma arc not only can heat the powder, but also can excite ultrasonic of different frequencies and different powers. The principles and characters of the plasma arc-excited ultrasonic were described, and the ultrasonic plasma spraying was compared with normal plasma spraying. Zirconia thermal barrier coatings (TBCs) were fabricated with two kinds of method. The TBCs were studied by the optical microscope observation, SEM observation and bonding strength experiment. The results show that suitable ultrasonic changes the performance and microstructure of TBCs in evidence. And the mechanism of ultrasonic influencing the TBCs was also discussed.     

Problems in High Current Density Nickel and Chromium Deposition

Five optical methods are discussed here by which the surface finish of polished or electrodeposited metal surfaces may be studied. Four are dealt with briefly because they have been adequately described in the literature. The fifth is believed to be new in its application to metal finishing. Preliminary results obtained for polished brass surfaces and for various electrodeposited metal coatings are discussed.

The presence of an oxide film has a marked influence on the optical behaviour of a metal surface. The properties of such a film may be learnt from the methods here outlined. Of particular practical interest is the anodic oxide film, familiar long since as a surface finish for aluminium and of current interest as a possible protection for other metals. The methods described are of general application. Illustrations are provided of the results obtained on anodised tantalum surfaces.     

Influence of surface topography of arc-deposited TiN and sputter-deposited WC/C coatings on the initial material transfer tendency and friction characteristics under dry sliding contact conditions

The influence of surface topography of PVD coatings on the initial material transfer tendency and friction characteristics in dry sliding contact conditions has been investigated. A modified scratch test was used to evaluate the material transfer tendency between ball bearing steel and two different PVD coatings, TiN and WC/C, under dry sliding contact conditions. Post test characterisation of the contact surfaces was performed using SEM/EDS and AES in order to map the initiation points and mechanisms for material transfer. The results show that the resulting topography of the PVD coated surfaces is strongly dependent on both the substrate material topography and the topography induced by the coating deposition process used. In sliding contact with a softer surface the coating topography results in a significant material pick-up tendency of the PVD coated surfaces. The material pick-up is mainly controlled by the abrasive action of hard coating asperities and as a result a polishing post treatment of the as-deposited PVD coatings significantly reduces the material pick-up tendency. For the WC/C coating, showing intrinsic low friction properties, the post treatment inhibits the material pick-up and results in a low and stable friction coefficient (μ ~ 0.1). For the TiN coating, that lacks intrinsic low friction properties, the post treatment reduces the material pick-up tendency but has no significant influence on the friction characteristics. This is mainly due to the presence of metallic Ti originating from the macroparticles on the TiN coating which results in a reactive surface that promotes a strong adhesion between the mating surfaces.     

用EPR法评价奥氏体不锈钢的敏化程度——材质因素及敏化条件的影响

用电化学方法(EPR 法)研究了不同材料和各种敏化条件对奥氏体不锈钢敏化程度的影响,并采用摸拟贫铬区的 Fe-11%Ni-Cr(6～18%)钢,研究了 EPR 法的特性.发现对不含 Mo 的钢而言,贫铬区的铬含量在16%以下时,就发生再活化溶解,因此,EPR 法比 Strauss 法更灵敏。试验后试样表面的金相观察发现:在晶界或夹杂物周围,首先发生方向性侵蚀点,然后,连结成腐蚀沟.     

Reactive atom plasma (RAP) figuring machine for meter class optical surfaces

A new surface figuring machine called Helios 1200 is presented in this paper. It is designed for the figuring of meter sized optical surfaces with form accuracy correction capability better than 20 nm rms within a reduced number of iterations. Unlike other large figuring facilities using energy beams, Helios 1200 operates a plasma torch at atmospheric pressure, offers a high material removal rate, and a relatively low running cost. This facility is ideal to process large optical components, lightweight optics, silicon based and difficult to machine materials, aspheric, and free form surfaces. Also, the surfaces processed by the reactive atom plasma (RAP) are easy to fine polish through hand conventional sub-aperture polishing techniques. These unique combined features lead to a new capability for the fabrication of optical components opening up novel design possibilities for optical engineers. The key technical features of this large RAP machine are fast figuring capabilities, non-contact material removal tool, the use of a near Gaussian footprint energy beam, and a proven tool path strategy for the management of the heat transfer. Helios 1200 complies with the European machine safety standard and can be used with different types of reactive gases using either fluorine or chlorine compounds. In this paper, first the need for large optical component is discussed. Then, the RAP facility is described: radio frequency R.F generator, plasma torch, and 3 axis computer numerically controlled motion system. Both the machine design and the performance of the RAP tool is assessed under specific production conditions and in the context of meter class mirror and lens fabrication.     

Predicting reflections of thin coatings

The appearance of materials and objects is important in for example household products, furniture, cars. Industries constantly adjust their fabrication parameters in order to create materials displaying the required properties. This is very time consuming and can be optimized with optical models. In literature optical models are to simulate the reflection of surfaces, but these reflections are never linked to their visual perception. In this research we aspire to create a link between the optical models and the visual perception of the surface. Steel was chosen as a case study because of its use in a wide variety of applications where the appearance of the steel is of paramount importance. Two parts are discerned in this paper: first different degrees of roughness were introduced on the steel substrates. Secondly a transparent coating is applied on the rough surfaces. The experimental data were used to predict the reflection of the surface.     

Thermal conductivity of high-temperature Si–B–C–N thin films

In this study, thermal transport was investigated for ceramic films with different silicon, boron, carbon, and nitrogen (Si–B–C–N) compositions. In order to investigate the effect of morphology on thermal barrier properties, the microstructure of these materials was varied from amorphous to nanocrystalline. Thermal conductivity trends of several ceramic thin films were characterized with a time-domain thermoreflectance (TDTR) technique. Samples containing two different Si–B–C–N chemical compositions were created by reactive magnetron sputtering and then subjected to annealing at temperatures up to 1400 °C. The room temperature thermal conductivity of the samples prepared via a 50% Ar/50% N₂ gas mixture remained constant near 1.3 W m⁻¹ K⁻¹, while samples prepared via a 75% Ar/25% N₂ gas mixture exhibited an increase in the thermal conductivity of 2.2 W m⁻¹ K⁻¹ (or higher). X-ray diffraction data demonstrated that the former samples were amorphous, while the latter samples formed silicon nitride (Si₃N₄) crystals. The experiments reveal which Si–B–C–N film composition remains stable in the amorphous state at high temperatures, thereby retaining lower thermal transport properties. These material aspects are ideal for thermal barrier applications such as non-oxide based ceramic coatings for high-temperature protective systems of aircrafts, as well as surfaces of cutting tools and optical devices.     

Electrodeposition of black chromium from environmentally electrolyte based on trivalent chromium salt

Thin films of black chromium have been prepared by electrodeposition technique on steel substrates. Deposition of 1 µm thickness is conducted in a solution of chromium trivalent salt and oxidizing agent fluorosilicic acid (H₂SiF₆) operated at a current density 350 mA cm^− 2 at 25 °C and 1 min. The influence of H₂SiF₆ concentrations on the trivalent chromium electrodeposition was studied by the potentiodynamic technique. The phase structure and surface morphology of the deposited films were examined by using X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The chemical composition of these thin films was determined by energy dispersive X-ray analysis (EDS) and X-ray photoelectron spectroscopy (XPS) analysis. The spectral reflectance in the visible light, for films coating was characterized. From the SEM analysis, it was found that the black chromium has nano lamellar morphology that leads to a strong dispersion level. The XRD results showed that chromium, chromium oxide and cobalt oxide are the main bulk chemical compounds in the films. However, from XPS analysis of these surfaces, it was possible to determine that the most external layers of the films are made of different kinds of chromium and cobalt compounds. The black chromium-cobalt alloy thin film has better optical properties to transform solar energy into thermal energy, and these properties remain practically constant even when heat treated to a high temperature, 400 °C for 24 h.     

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.