Hinge-type knee prosthesis wear tests with a mechanical load and corrosion properties monitoring

The primary goal was to compare model replacements with and without DLC layer. Components were made of the Ti6Al4V alloy and coated with a DLC layer, the sliding sleeve made of a PEEK polymer. Testing was done in the saline physiological solution (9 g/L NaCl). The measuring system was supplemented with the corrosion behavior monitoring.The results show that the applied DLC coating significantly increases the service life of the implant. Based on the results it is possible to state that an accurate mechanical load together with corrosion behavior monitoring shifts testing in the given field to a qualitatively higher level.     

Progressive and constant load scratch testing of single- and multi-layered composite coatings

The development of effective coating systems that offer high protection against erosion–corrosion is of utmost importance in several industrial sectors. Such a coating class is typically designed to provide an effective barrier against aggressive environments combined with cathodic protection. The adherence to the substrate ensures full performance and reliability of the coatings during service. In the present investigation, the scratch response of single- and multi-layered composite coatings made from superimposed layers of a modified phenyl–methyl silicone resin and of aluminum–magnesium (Al–Mg 4.5 wt%) metallic powders was investigated. The applied loads, the contact conditions between the indenter and coating surface and the sliding speeds were analyzed, and empirical models were developed accordingly. The scratch response of the composite coatings was mapped according to the testing conditions, thus providing a useful instrument for designers and practitioners.     

Investigating Corrosion Performance and Corrosive Wear Behavior of Sol–gel/MAO-Coated Mg Alloy

In this study, a hydroxyapatite composite coating was prepared by a sol–gel technique on the micro-arc oxidation (MAO)-coated AZ31 Mg alloy to seal the micro-pores. The composite coating achieved a larger hardness value and two times thickness more than pure MAO coating. The corrosion and wear resistance of the sol–gel/MAO coating in simulated body fluid were investigated compared to MAO coating. It was found that the composite coating presented a positive corrosion potential and a lower corrosion current density than MAO coating. The sol–gel/MAO composite coating could provide more effective barrier against corrosive ions than single MAO coating for AZ31 alloy. In the wear tests, a ball-on-disk tribometer was used to study the effect of loads on the wear properties of the coatings at 37 °C. The wear resistance of sol–gel/MAO composite coatings was apparently superior to MAO coating. The wear mechanisms of abrasion and adhesion in composite coatings are investigated. Finally, two physical models for the corrosion and sliding wear mechanisms of sol–gel/MAO composite coatings are proposed, respectively.     

Friction and Thermal Effects of Engineering Plastics Sliding Against Steel and DLN-Coated Counterfaces

Polymers are increasingly used in tribological applications, because of their self-lubricating ability, corrosion resistance and chemical compatibility. However, their performance depends strongly on the parameters of the total tribological system. Not only polymer characteristics, but also counterface properties become important because of their influence on friction and wear, on surface energy and on the thermal conductivity of the total system. Applying a Diamond-Like Nanocomposite (DLN) coating on a steel counterface can improve the tribological behaviour of the sliding couple under certain conditions. In the case of metal sliding against DLN, the high hardness and the wear resistance of the coating is advantageous for better tribological properties. However, for polymers sliding against DLN, the lower thermal conductivity of the DLN coating compared with a steel mating surface dominates friction and wear. In case of polyamides this results in worse tribological performance in contact with the DLN coating, because of polymer melting. In the case of more rigid polymers, such as, e.g., POM-H and PETP, lower coefficients of friction lead to lower frictional heat generation. In these cases, the thermal characteristics of the counterface are less important and the lower surface energy of the DLN coating is favourable for decreased adhesion between the polymer and the coating and consequently better tribological properties.     

SiC纳米粒子增强锌铝基耐蚀涂层的制备及性能研究

为解决锌铝基耐蚀涂层在高速、强摩擦等特殊服役条件下的使用问题，探索性地添加SiC纳米粒子对锌铝基耐蚀涂层进行改性，以提高涂层的硬度和强度。研究了SiC纳米粒子及其添加量对涂层硬度、附着强度、耐冲击性能和耐腐蚀性能的影响，并对涂层的微观组织和成分进行了分析。结果表明，添加SiC纳米粒子可显著提高锌铝基耐蚀涂层的硬度，且没有对涂层的附着强度、耐冲击性能和耐腐蚀性能带来负面影响。SiC纳米粒子在涂层中的均匀分散是保障涂层综合性能优异的必要条件。     

Large-scale friction and wear tests on a hybrid UHMWPE-pad/primer coating combination used as bearing element in an extremely high-loaded ball-joint

The surfaces of a heavily loaded ball-joint were initially covered with a sliding spray and suffer wear. A solution is found by incorporating UHMWPE pads (Ultra high molecular weight polyethylene) with a carbon fibre/epoxy reinforced ring as sliding material into the chairs of the structure, while the steel ball-side is covered with a Zn-phosphate primer coating, protecting against corrosion. The local static and dynamic behaviour of the hybrid UHMWPE pads in contact with steel or Zn-coated counterfaces has been large-scale tested on loading capacity, low friction and wear resistance. For protection of the sliding counterface against wear, a polymer lip covering the carbon ring has been experimentally designed to flow over the carbon ring under high contact pressures, assuming the retained polymer disc under hydrostatic conditions. As such, the soft coating resists extremely high contact pressures (150 MPa) with good adhesion to the steel ball. However the application method should be carefully selected, sprayed coatings are the most favourable for low initial static friction. Calculated bulk and flashtemperatures revealed that the UHMWPE melting temperature is not exceeded, although softening of the coating under high contact pressures may be favourable for a ‘self-repairing’ ability. Pre-sliding creep and intermediate wear paths as manifesting in the ball-joint were simulated, indicating that the maximum design coefficient of friction is not exceeded. Test results are compared to FEM-calculations to verify the practical applicability of the modified sliding system.     

激光熔覆陶瓷涂层研究现状与展望

陶瓷材料具有高硬度、高熔点、高耐蚀等特性,常被应用于机械装备关键零部件的表面强化改性和再制造修复。随着装备服役工况日益苛刻,传统金属材料所制备的装备运动部件在服役过程中易于发生磨损、腐蚀、变形等失效,进而导致服役性能退化,严重时甚至引发装备恶性故障。激光熔覆作为一种高效的表面强化和再制造技术,在提升基材表面耐磨、耐蚀、耐热、抗高温氧化等性能方面具有重要应用前景。通过激光熔覆技术在零部件表面制备陶瓷涂层,对于延长关键零部件寿命、提高资源利用率、节约稀贵金属材料具有重要意义。首先按照陶瓷涂层的组织结构和成形机理对激光熔覆陶瓷涂层进行了分类介绍;然后结合激光熔覆制备陶瓷涂层的典型缺陷详细阐述了涂层质量优化的常用方法;而后综述了激光熔覆陶瓷涂层在提升零件耐腐蚀、耐磨损、耐高温性能和提高生物相容性等方面的应用情况;最后,总结了激光熔覆陶瓷涂层技术发展现状,并展望了激光熔覆陶瓷涂层技术的发展趋势。     

Time‐lapse lab‐based x‐ray nano‐CT study of corrosion damage

An experimental protocol (workflow) has been developed for time‐lapse x‐ray nanotomography (nano‐CT) imaging of environmentally driven morphological changes to materials. Two case studies are presented. First, the leaching of nanoparticle corrosion inhibitor pigment from a polymer coating was followed over 14 days, while in the second case the corrosion damage to an AA2099 aluminium alloy was imaged over 12 hours. The protocol includes several novel aspects relevant to nano‐CT with the use of a combination of x‐ray absorption and phase contrast data to provide enhanced morphological and composition information, and hence reveal the best information to provide new insights into the changes of different phases over time. For the pigmented polymer coating containing nominally strontium aluminium polyphosphate, the strontium‐rich components within the materials are observed to leach extensively whereas the aluminium‐rich components are more resistant to dissolution. In the case of AA2099 it is found that the initial grain boundary corrosion is driven by the presence of copper‐rich phases and is then followed by the corrosion of grains of specific orientation.     

装配结合面防护技术研究

采用加速试验方法,研究了环境对Q235钢板和5A05铝板螺接件的装配结合面在12种防护处理措施下的防腐性能。提出了几种适用的装配结合面防护技术,并给出了不同条件下的装配防护材料及工艺方案。结果表明,采用适当的装配结合面防护技术可以提高雷达构件的防腐蚀性能。其中,采用3号船用润滑脂安装、底漆湿装配和缓蚀剂的合理使用是比较有效的方法。     

热电厂锅炉水冷壁热腐蚀治理技术及其应用

锅炉水冷壁热腐蚀已成为热电厂亟待解决的问题。介绍了国内外锅炉管道表面防护技术的概况，提出笔研制的高速电弧喷涂SL30涂层 高温封孔剂的防护体系。通过在天津大港电厂和邯郸电厂等锅炉水冷壁的实际应用，证明高速电弧喷涂SL30涂层 高温封孔涂剂层体系的防腐效果明显，实践表明采用热喷涂技术治理热电厂锅炉水冷壁热腐蚀问题有良好的应用前景。     

Adhesion Force Measurements of Polymer Particles by Detachment Field Method

The adhesion force distributions of polymer particles to aluminum substrates were measured by the detachment field method. Polymer particles with conducting surface treatment were used for the measurements.Further the conventional detachment field method was modified to be applicable to the adhesion force measurements of a single particle. The adhesion force of the polymer particles increased with an increase in relative humidity. The surface roughness of the substrate influenced the adhesion forces of particles significantly. The influence of the CF4 plasma treatment of the polymer particles and thin layer coating of the substrate surface on the adhesion forces of the polymer particles was also studied, and factors affecting adhesion forces of polymer particles are discussed.     

Microwave Nondestructive Detection of Corrosion Under Thin Paint and Primer in Aluminum Panels

Detection of corrosion, under paint and primer, in various metallic structural components, particularly when used in moist and salty environments is an important practical concern. Moreover, nondestructive testing techniques that do not require paint removal are desired. Near-field microwave nondestructive inspection techniques, employing open-ended rectangular waveguide probes, have shown tremendous potential for detecting and evaluating the presence of corrosion under paint in steel substrates. The objective of this investigation has been to investigate the potential of these techniques for detecting corrosion under paint and primer in aluminum substrates. To accomplish this goal, an electromagnetic formulation, simulating detection of corrosion in layered structure using open-ended rectangular waveguide probes, was used to gain an insight into the functionality of measurement parameters such as the frequency of operation and standoff distance. In conjunction with this simulation, the dielectric properties of paint, primer, real and chemically produced aluminum oxide were measured in a wide range of microwave frequencies (2.6–18 GHz). The results showed that the dielectric properties of paint, primer and aluminum oxide are very similar to each other. Subsequently, the theoretical simulation was conducted in a wide frequency band (8.2–40 GHz). The overall result of the simulation effort was that higher frequencies and standoff distances of a few mm are more optimal for detecting thin corrosion layers under paint. Two specially prepared aluminum panels with induced areas of corrosion and surface pitting were produced as well. Using these panels and several phase sensitive measurement systems, experiments were conducted producing 2-D images of various areas of these panels. Images were produced at different standoff distances and at frequencies of 9, 11.725, 24.1, and 33.5 GHz. The overall results of the experimental investigation were extremely promising when detecting the thin regions of corrosion in these panels. This paper presents the approach and results of this investigation.     

高分子复合材料包胶在带式输送机滚筒上的应用

滚筒作为带式输送机设备的重要部件,磨损失效严重,使用寿命短,维修更换成本高。新型高分子复合材料包胶具有优异的耐磨性、抗撕裂性、吸振性和自净性,通过实际使用情况分析,验证了其在提高滚筒寿命、节约成本等方面的重要作用,值得大力推广。     

Extending the life of tight joints by polymer-coating application to the shaft surface

Polymer coatings may be used in tight joints to prevent fretting corrosion. The constraint on their use is the polymer adhesion with the metal. A method of calculating the life of such joints is presented.     

军用电子设备的涂装体系概论

本文根据军用电子设备的实际使用环境条件 ,探讨了不同的基体金属表面、不同的零部件的涂装体系的构成及防护性能 ,电子设备的基本油漆涂层和终饰油漆涂层系统及选用原则 ,简要介绍了地面、舰船、机载电子设备的涂装体系。     

高速钢领表面涂层技术的新发展

分析了目前适合细纱机钢领专件的各种表面涂层技术的发展.特别是对性价比优、摩擦系数小、耐磨、防腐的表面涂层进行了分析,列举了一些适合钢领表面涂层的新技术,如镀铬、镍磷复合镀、金刚石涂层、纳米镀膜、非晶态以及自润滑等表面处理技术,有的已经开始使用这些表面处理,而有的还需要在生产实践中进一步探索.     

Influence of layer thickness on hardness and scratch resistance of Si-DLC/CrN coatings

Abstract

Multifunctional coatings, widely used in tribological applications, have their properties strongly influenced by the interaction of the system coating/substrate. The use of multilayered coatings has been pointed out as a solution for the problem of high internal stresses that can be generated in coated systems, in particular in the case of soft substrates. In multilayered coatings, a decrease in the stress gradient between substrate and coating improves adhesion. Moreover, the thickness of the coating has shown a strong influence on the tribological behaviour of the coated system. This paper, through widely used and efficient techniques, seeks to assess the influence of the thickness of different layers (DLC and CrN) on the response of a multifunctional coating. Si rich DLC and CrN coatings with different thicknesses were deposited on a steel substrate (AISI 1020) by Plasma Enhanced Magnetron Sputtering (PECVD). Scanning electron microscopy (SEM) and Raman spectroscopy (RS) were used in order to characterize the chemical composition and microstructure of the coatings. Instrumented indentation and scratch test techniques were used to measure hardness, elastic modulus, and adhesion of each layer. Critical loads were determined by visual analysis, using SEM in conjunction with the curves obtained in the scratch tests. The evaluation of the effect of the thicknesses of the layers allowed an optimised design of the multifunctional coated systems with improved durability.     

Investigation of antiwear coatings deposited by the pvd process

The tribological properties of various PVD‐deposited coatings (vacuum arc method) have been tested, both single‐layer coatings (TiN, CrN, Ti(C,N), and Cr(C,N)) and multilayer coatings (Cr(C,N)/CrN/Cr and CR(C,N)/(CrN+Cr₂N)/CrN/Cr). An unlubricated ball‐on‐disc tribosystem was used in which an Al₂O₃ ball is pressed against a coated steel disc rotating in the horizontal plane. A novelty of the method is the removal of wear debris from the contact zone using a draught of dry argon. This improves the repeatability of the test results and the stability of the tribological characteristics. It is shown that CrN coatings exhibit the best antiwear properties and Ti(C,N) the worst. Multilayer coatings have better antiwear properties than single‐layer ones. The friction coefficients for CrN and Cr(C,N) coatings are much smaller than for the commonly used TiN. A correlation has also been found between the physical properties of the coatings tested (adhesion of the coating to the substrate assessed in scratch tests, and coating hardness) and their antiwear properties. An improvement in coating‐substrate adhesion results in wear reduction, while greater hardness (causing a coating embrittlement increase and a change in the wear mechanism) brings about greater wear. There is no correlation between the physical properties and the friction coefficients of the coatings tested.     

Effects of shielding coatings on the anode shaping process during counter-rotating electrochemical machining

Electrochemical machining (ECM) has been widely used in the aerospace, automotive, defense and medical industries for its many advantages over traditional machining methods. However, the machining accuracy in ECM is to a great extent limited by the stray corrosion of the unwanted material removal. Many attempts have been made to improve the ECM accuracy, such as the use of a pulse power, passivating electrolytes and auxiliary electrodes. However, they are sometimes insufficient for the reduction of the stray removal and have their limitations in many cases. To solve the stray corrosion problem in CRECM, insulating and conductive coatings are respectively used. The different implement processes of the two kinds of coatings are introduced. The effects of the two kinds of shielding coatings on the anode shaping process are investigated. Numerical simulations and experiments are conducted for the comparison of the two coatings. The simulation and experimental results show that both the two kinds of coatings are valid for the reduction of stray corrosion on the top surface of the convex structure. However, for insulating coating, the convex sidewall becomes concave when the height of the convex structure is over 1.26 mm. In addition, it is easy to peel off by the high-speed electrolyte. In contrast, the conductive coating has a strong adhesion, and can be well reserved during the whole machining process. The convex structure fabricated by using a conductive iron coating layer presents a favorable sidewall profile. It is concluded that the conductive coating is more effective for the improvement of the machining quality in CRECM. The proposed shielding coatings can also be employed to reduce the stray corrosion in other schemes of ECM.     

Erosion–corrosion performance of high-Cr cast iron alloys in flowing liquid–solid slurries

In many slurry transportation systems, such as in FGD (Flue Gas Desulphurization) and chemical processing applications, corrosion and erosion are the two main mechanisms of material degradation of the pump wet-end components including pump casing, impeller and liners. The performance of a selected material is mostly dependent upon its relative corrosion and erosion resistance to the service environment. In these cases erosion, corrosion and the related synergistic effects can be very complicated since they are affected by numerous factors including solid and slurry properties, chemical contents, hydraulic conditions and temperatures. In this experimental study, sliding Coriolis erosion testing has been performed with various corrosion factors such as pH value, chlorides content and temperature to evaluate the erosion–corrosion resistance of some high-alloyed white cast irons containing different levels of chromium and other elements. Optical microscope and SEM-EDS have also been used to examine microstructure and surface conditions of tested materials. Results indicated that material loss due to corrosion factors increased as acidity-chlorides and temperature increased. At relatively high corrosion intensity, the white cast irons with higher alloy content (especially chromium) clearly showed improved corrosion resistance and combined erosion–corrosion resistance over those with lower alloy content. Under certain corrosion and hydraulic conditions, particle size is perhaps the single most influential factor on erosion–corrosion rate of the high-Cr cast iron alloys. Relatively large particles are much more effective than small ones at removing both the corroded surface layer and the fresh material, causing substantially higher rate of material loss. Some other related factors have also been addressed.