镍基单晶高温合金扩散阻挡层的研究进展

综述了镍基单晶高温合金扩散阻挡层的国内外研究进展。简要介绍了高温防护涂层/镍基单晶高温合金基体元素的互扩散现象,说明了扩散阻挡层的作用机理,阐述了扩散阻挡层的设计原则和要求,通过对比分析了各类扩散阻挡层的优缺点。最后对镍基单晶高温合金用扩散阻挡层的研究做出了展望。     

钼及其合金氧化防护涂层的研究进展

钼及其合金具有较好的高温力学性能和良好的耐腐蚀性能,然而高温氧化问题限制了钼及其合金的应用。分别从涂层体系、涂层结构及涂层的制备工艺3个方面综述了近年来国内外钼及其合金氧化防护涂层的研究进展。在涂层体系方面,目前的研究主要集中在钼的硅化物(如MoSi2涂层)上;在涂层结构方面,对比了各种结构涂层的特点,单一涂层与基体存在热膨胀不匹配问题,使得单一涂层作为高温防护的应用受到限制,然而复合涂层却明显改善了此缺点;在涂层的制备工艺方面,介绍了涂层的各种制备工艺及其优缺点。综合应用各种涂层制备工艺,发展新型复合涂层是今后钼及其合金氧化防护涂层的发展方向。     

铌合金高温热防护及其抗氧化硅化物涂层

铌及其合金具有熔点高、密度适中、易焊接、高温强度和可加工性能良好等特点,被认为是理想的应用在1200～1500℃高温结构热端部件的候选材料,但其较弱的抗氧化性能是工程化应用的瓶颈。综述了铌及其合金的高温氧化特点和热防护方法,指出涂层方法是铌及其合金走向工程化应用的关键。介绍了近年来应用于铌及其合金表面的抗氧化涂层体系,其中硅化物涂层热防护体系因其表面能形成分布均匀、组织稳定且热扩散速率低的硅酸盐玻璃而抗氧化性能优异。总结了硅化物涂层的主要制备方法和组织特点,并对所得涂层的抗氧化性能进行了分析对比,指出抗氧化硅化物涂层的制备技术复合化是未来发展的方向。抑制硅化物涂层与铌及其合金基体的反应互扩散,进一步提高抗氧化硅化物涂层的使用温度,增加涂层的隔热性能、降低涂层的热发射率是未来亟待解决的问题。     

IC6合金NiCoCrAlY涂层在制造过程中的修复研究

研究了适用于IC6合金的NiCoCrAlY涂层在制造过程中的修复对涂层本身及IC6合金基体的显微组织和力学性能的影响。结果表明，与原始态涂层相似，修复态涂层通过扩散层与基体紧密结合，涂层/基体界面还没有任何孔洞和裂缝，各元素在涂层、基体之间存在明显的浓度梯度，而且涂层修复对IC6合金的显微组织和力学性能均没有明显影响，经过1100℃/90MPa持久试验后，原始态涂层和修复态涂层与IC6合金基体之间都发生了明显的互扩散，涂层中Mo含量上升到16%（质量分数，下同）左右，而Cr和Co含量下降至5%左右，但涂层仍然与合金基体结合紧密，因此，NiCoCrAlY涂层在制造过程中的修复是可行的。     

难熔金属表面高温防护涂层抗热震性能研究现状

难熔金属及其合金具有高温强度优异、加工塑性好、耐腐蚀性好等优点,在航空、航天和核工业领域中得到了广泛应用,是一种重要的高温结构材料。但难熔金属及其合金因其自身易氧化的缺点,导致材料在未达到服役温度时就发生严重氧化,从而快速失效。目前,高性能高温防护涂层是保障难熔合金服役性能的关键,然而难熔金属及其合金表面高温防护涂层的实际服役工况非常苛刻,往往伴随着强热震,是导致涂层失效的重要原因。因此,难熔金属表面高温防护涂层在具备优异恒温抗氧化性能的前提下,还需具备良好的抗热震性能。综述了难熔金属表面高温防护涂层的热震失效机制,讨论了影响涂层抗热震性能的关键参数;阐述了难熔金属表面硅化物、金属和复合涂层3类主要涂层体系抗热震性能的研究现状,重点回顾了优化涂层结构、添加陶瓷颗粒以及设计复合涂层等提高涂层抗热震性能的方法及其改善效果;最后,从降低涂层与基体间的热膨胀系数失配度、改善基体/涂层界面结合性能以及设计复合梯度涂层3个方面展望了未来难熔金属高温防护涂层的发展方向。     

MoNbTaTiW难熔高熵合金表面硅化物涂层的制备与抗氧化机理

解决难熔高熵合金在高温下的抗氧化问题是其应用于工程的前提,在难熔金属表面制备抗氧化涂层是提高其抗氧化性能的有效途径。采用料浆熔烧法在MoNbTaTiW难熔高熵合金表面制备复杂硅化物抗氧化涂层（Si-20Cr-20Fe）,利用扫描电镜（SEM）、能谱仪（EDS）和X射线衍射（XRD）等研究原始硅化物涂层及其在1 300℃氧化后的显微结构、物相和成分,探讨Si, Fe, Cr在涂层中的扩散规律和涂层的抗氧化机理。结果显示：熔烧后的原始硅化物涂层由金属与硅反应生成的二硅化物、5/3硅化物和三元硅化物Cr₄Nb₂Si₅组成,硅化物涂层与基体之间形成了良好的扩散反应界面。1 300℃氧化后,Si, Fe, Cr 3种元素向基体扩散,扩散反应界面向基体方向移动,涂层厚度增加,扩散反应界面的结构与成分与原始复杂硅化物涂层的无显著差别。氧化后涂层表面形成了由CrNbO₄,SiO₂,WO₃和Fe₂SiO₄组成的无裂纹致密氧化物层,...     

NiCoCrAlYHf涂层与一种Ni基单晶高温合金循环氧化行为研究

在第三代Ni基单晶高温合金上制备NiCoCrAlYHf(HY5)高温抗氧化涂层,采用扫描电镜(SEM),能谱分析(EDS)和X射线衍射(XRD)等手段,对涂层表面及界面进行组织形貌观察和相结构分析,研究涂层试样的循环氧化动力学和元素互扩散行为。结果表明:采用真空电弧镀(AIP)方法制备的HY5涂层,提高了单晶高温合金的循环抗氧化能力;在1100℃大气环境中扩散600h后,涂覆HY5涂层的单晶高温合金基体中形成了互扩散区IDZ,互扩散主要由Cr,Ni元素从基体向高温抗氧化涂层的外扩散以及Al元素从高温抗氧化涂层向基体的内扩散构成;在涂层下方60μm左右有拓扑密堆相TCP析出,并形成二次反应区SRZ。     

镍基喷焊涂层与钛合金基体界面特征的研究

考察了三种工艺制备的镍基喷焊涂层与钛合金基体结合界面的组织形貌、涂层横切面上合金元素的扩散和显微硬度的变化,分析了它们的界面特征及影响因素.结果表明:镍基喷焊涂层与基体钛合金的结合是基于合金元素扩散的冶金结合,合金元素的扩散对涂层与基体能否形成冶金结合具有决定性的影响,钛合金表面的活化处理、涂层合金重熔时液态停留时间以及喷焊后进行时效处理是影响合金元素扩散的主要因素.     

电弧离子镀TiC扩散障结构及抗高温氧化性能研究

采用电弧离子镀技术(AIP)在NiCrAlY涂层与镍基高温合金(DD3合金)之间沉积TiC薄膜作为扩散障层,研究了TiC对NiCrAlY涂层与基体的元素互扩散的阻碍作用和对涂层氧化动力曲线的影响。对于添加扩散障层前后的试样,进行循环抗氧化试验来评价其抗高温氧化性能,并用扫描电镜(SEM)分析氧化前后试样微观形貌和成分,用X-射线衍射仪分析涂层的相结构。试验结果表明:TiC有效阻滞DD3基体与涂层之间的元素互扩散,提高了NiCrAlY涂层和DD3合金的抗高温氧化性能。     

喷涂及激光熔覆制备难熔金属涂层的研究现状

钼、钽、钨、铌及其合金等难熔金属具有高熔点、良好的高温性能等特点，在防护领域发挥重大作用，但其成本高，且由于熔点高、导热低、脆性大导致其加工比较困难。通过特定工艺在基体表面制备难熔金属涂层，可以在不改变基体性能的基础上使其具有难熔金属优良的力学性能、高温性能，且能够有效降低制造成本，对于装备表面防护具有重大的研究价值。鉴于难熔金属涂层在制造业中发挥着越来越重要的作用，首先介绍了钼、钽、钨、铌等难熔金属涂层的等离子喷涂、爆炸喷涂、激光熔覆及冷喷涂制备技术，总结了各工艺特点。在此基础上，分析对比了不同工艺制备难熔金属涂层的微观组织及性能，归纳了从涂层材料成分及结构、工艺参数及后处理3个方面做出的改进进展。最后对难熔金属涂层制备技术发展尚存的问题与发展方向进行了展望。     

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.     

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.……     

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...     

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.     

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.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

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.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...