面向高端装备关键构件的纳米热喷涂涂层

"中国热处理与表层改性技术路线图"指出[1]:"热处理与表层改性技术作为先进材料和高端装备制造的核心技术、关键技术、共性技术和基础技术,是国家核心竞争力,在中国走向材料强国和机械制造强国的进程中有着举足轻重的作用"。热喷涂技术作为先进的表面层改性技术可以大量应用于高端装备关键构件上。纳米热喷涂涂层技术是纳米材料和热喷涂技术的结合和综合应用,长期以来都作为一个特殊的应用领域受到西方发达国家军方和工业界的高度重视,这是因为飞机、舰船等各种高端装备都面临着极端的服役条件。列举了热喷涂的纳米结构耐磨抗蚀陶瓷涂层、纳米结构双陶瓷热障涂层、纳米改性MCrAlY合金涂层和替代镀硬铬的纳米改性金属陶瓷涂层的研究进展,说明纳米结构和纳米改性热喷涂涂层在高端装备关键构件上有着非常广阔的应用前景。强国强军,就应刻不容缓地发展纳米热喷涂技术。     

一种新型的热喷涂材料

热喷涂技术已经成为现代工业中不可或缺的一种重要技术,自热喷涂技术出现以来,人们就在不断寻找各种热喷涂材料,目前大部分金属和陶瓷都可采用热喷涂技术。高熵合金是近年来发展起来的一类新型合金,由于高混合熵效应导致这类合金具有许多优异的性能,适用于装备和零件的表面防护。利用热喷涂技术在装备和零件表面制备高熵合金涂层,可以充分发挥高熵合金的耐磨、防腐等性能,有效提高装备使用寿命。简要阐述了高熵合金的定义、组织结构和性能特点,展望了热喷涂高熵合金涂层的应用前景,并分析了高速电弧喷涂FeCrNiCoCu(B)高熵合金涂层的微观组织和常规力学性能。     

表面处理技术对钛合金疲劳性能影响的研究进展

针对钛合金表面硬度较低、耐磨性较差、易高温氧化等缺陷,选择适当的表面处理技术能够使其得以改善。由于钛合金对疲劳性能十分敏感,在表面处理过后,对其疲劳性能有较大影响。因而本文归纳了钛合金表面处理的多种方法,如电镀、化学镀、热喷涂、激光处理、阳极氧化、微弧氧化、物理气相沉积技术等。根据钛合金疲劳断裂现状及表面改性技术的特点,讨论了表面技术的应用、材料的选择和结构的设计对钛合金基体疲劳性能的影响。分析并总结了涂层在疲劳断裂过程起到的作用及影响疲劳性能的的主要原因,展望了未来钛合金表面改性方法、涂层材料及结构的研究趋势。以期为制备高强度、耐摩擦磨损和提升钛合金基体疲劳性能的表面改性涂层提供参考。     

电脉冲处理对金属材料组织、力学性能影响的研究进展

多能量场辅助材料加工成形是先进制造技术发展的重要方向，其中电脉冲处理(EPT)是一种利用脉冲电流实现材料微观组织调控与力学性能改善的新型处理技术，在辅助金属材料制备和加工等领域有着广阔的应用前景。电脉冲处理具有能量利用率高、作用时间短等优点，在提高材料塑性、促进再结晶和相变等方面具有传统热处理无法比拟的优势。近年来，金属材料组织、力学性能对电脉冲处理的响应行为受到国内外学者的广泛关注。当脉冲电流加载于金属材料时，电场作用下的漂移电子与材料内部组织会发生相互作用，产生焦耳热效应、电迁移效应等电致塑性效应。因此，电脉冲处理能够增强原子扩散、促进位错运动，提高材料塑性变形能力。同时，脉冲电流能够显著促进晶粒细化、固态相变与织构弱化，从而使材料获得优异的综合力学性能。此外，电脉冲处理还可以实现材料内部孔洞和微裂纹的修复，有效抑制裂纹的扩展，从而提高材料的断裂韧性和延长材料的疲劳寿命。本文基于现有研究现状，从晶粒细化、固态相变、裂纹修复等方面，总结分析了电脉冲处理对金属材料微观组织和力学性能的影响规律与作用机制，同时，简要介绍了电脉冲处理改善焊接接头成形特征和性能的相关研究，最后对电脉冲处理技术...     

热喷涂金属陶瓷涂层复合磨损失效机制

热喷涂金属陶瓷涂层由于具有优异的耐磨性能,广泛应用于机械零部件的性能提升。热喷涂金属陶瓷涂层在复杂工况中服役时,在多种外界因素的复合作用下,会发生由磨粒磨损、腐蚀磨损、冲蚀磨损、疲劳磨损中的一种或几种作用导致的失效。结合涂层的服役工况和其自身结构特点归纳分析了热喷涂金属陶瓷涂层的复合磨损失效机制,并对热喷涂金属陶瓷涂层复合磨损失效研究的发展方向进行了展望。     

重熔处理热喷涂层的研究现状及展望

重熔处理是改善热喷涂层组织并提高其性能的有效方法。综述了近年来国内外热喷涂层的重熔处理工艺,并阐述了自熔合金、非自熔合金和金属陶瓷涂层的重熔特点和研究现状,最后对热喷涂层重熔技术的发展方向进行了展望。     

热喷涂Ni基金属陶瓷层的重熔处理研究进展与展望

热喷涂Ni基金属陶瓷涂层具有耐磨损、耐高温和耐腐蚀等优良性能,已被广泛应用于零件的修复,但是由于涂层中的气孔、微裂纹等微观缺陷较多,结合强度较低,在恶劣的环境中适应性较差。重熔处理可以提高此类涂层界面的结合强度、耐磨性及耐蚀性能,延长其使用寿命。介绍了每种Ni基金属陶瓷热喷涂层的重熔处理方法、性能和结构组织,指出了重熔处理存在的一些问题,并给出了未来研究的展望。     

热喷涂纳米结构涂层技术的研究进展

与传统材料的热喷涂涂层相比,纳米结构涂层在力学和摩擦学等方面的性能有了一定的提高.作者综述了国内外在应用热喷涂技术制备纳米结构涂层方面的研究进展.介绍了纳米结构喂料的制备、热喷涂纳米结构涂层的构筑方法、涂层的特殊性能以及应用情况.从目前国内外的情况来看,热喷涂纳米结构涂层技术的研究取得了较大的进展.随着技术、工艺的不断完善,其必将在很多领域取代传统的涂层.     

热喷涂制备二氧化钛涂层中锐钛矿相调控的研究进展

二氧化钛(TiO_2)涂层在许多领域具有重要的应用价值,如光催化降解和光电池,近年来引起了相关研究者的广泛关注。在众多涂层制备技术中,热喷涂技术可以快速、高效、大面积、大批量地制备TiO_2涂层,且得到的涂层力学性能良好,喷涂成本较为低廉,因而使热喷涂TiO_2涂层的应用更具前景。TiO_2涂层的晶相组成是影响涂层最终性能的一个重要因素,而控制涂层中晶相组成的关键是调控亚稳态的锐钛矿相含量。综述了近些年来国内外制备TiO_2涂层常用的热喷涂技术,如传统粉末热喷涂、液料热喷涂以及冷喷涂等,分别阐述了不同热喷涂技术中通过调节一些重要参数达到调控涂层中锐钛矿相的方法,并讨论了材料掺杂对TiO_2涂层中锐钛矿相的影响,指出了目前调控涂层中锐钛矿相存在的问题和后续的研究方向。     

热喷涂激光预处理的应用与影响研究进展

综述了激光预处理技术在热喷涂中的应用研究进展,通过调整激光工艺对基体进行清理或刻蚀处理,能够完成对基体表面的净化与粗化,提升涂层服役性能。分析了激光预处理对涂层性能的影响,激光预处理后能增强涂层在基体表面的机械结合,改善涂层/基体界面润湿,降低孔隙率。明确了激光预处理在热喷涂中存在的问题,并展望了其应用前景与研究方向。      

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Synthesis of Alumina-Zirconia Nanocomposites by Solgel Process

Al₂O₃-ZrO₂ nanocomposites were developed starting with the solgel process. Composite alumina-zirconia nanopowders were synthesized from metallorganic precursors (Aluminium secondary butoxide and zirconium Iso propoxide) using the solgel process. The parameters affecting the synthesis—solvent, concentration of precursor, R/H ratio (i.e., dilution of water in solvent)—were varied as also the temperature and pH. BET and TEM were used to measure nanosize. Diffuse reflectance spectroscopy and also qualitative optical absorption led to identical particle size estimate. The variation of process parameters was used to study the effect and interdependence of process parameters. Artificial Neural Networks was used to rigorously analyze the process. Although this led to confirmation of interdependence of parameters, the presence of a single overwhelming solvent variable was also established. Then the optimal process was used to synthesize more nanopowder. To produce bulk nanocomposite the nanopowders were sintered by varying the temperature and time period. The sintered lithoids were probed with a vickers hardness tester to measure elastic modulus, hardness, and fracture toughness. The results showed high elastic modulus, modest hardness, and very high fracture toughness.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Friction Stir Processing Strategies for Uniform Distribution of Reinforcement in a Surface Composite

Friction stir processing (FSP) is an important technique for preparing surface composites. Fabricating defect-free surface composites with uniform particle distribution by FSP is a challenging task. In this study, silicon carbide particles reinforced AA5083 alloy surface composites was fabricated using different FSP strategies including variation in process parameters, dual-tool processing and tool offset overlapping. Material flow of the processed material with reinforcement particles demonstrated that the distribution of particles was influenced by the stirring action of the probe as well as the extrusion of the plasticized material due to the movement of the tool. Process parameters, particularly rotational speed, showed a dominant influence on the distribution of silicon carbide particles.