再制造热喷涂层的残余应力与显微特征的对应关系

利用高效能超音速等离子喷涂(HEPS)、爆炸喷涂(DGS)和高速电孤喷涂(HVAS)三种热喷涂技术制备了不同厚度的Fe-Cr-B-Si和Fe-Cr-B-Si-Mo涂层,利用X射线应力测定仪测定了涂层表面残余应力,并得出表面残余应力与涂层厚度的关系曲线,进一步采用电解剥层法+X射线应力测定法研究了涂层应力沿厚度方向的分布...     

空气超音速火焰喷涂、冷喷涂与电镀制备电触头银层的组织结构与摩擦磨损性能对比

电触头是电力输送系统中的关键元器件,其失效方式与触头表面涂层的磨损密切相关。采用空气超音速火焰喷涂工艺(HVAF)和冷喷涂工艺(CS)分别制备了银涂层;采用往复摩擦试验研究了涂层在不同载荷、频率条件下的摩擦磨损性能,并与电镀银镀层的性能进行了对比;采用扫描电镜(SEM)和X射线能谱仪(EDS)研究了涂层磨痕的表面形貌和成分,并对涂层的摩擦磨损机理进行了分析和讨论。结果表明：空气超音速火焰喷涂和冷喷涂工艺均可制备较厚的致密银涂层;冷喷涂制备的银涂层硬度较高,在高频、高载荷条件下具有较小的摩擦系数和较低的磨损量;空气超音速火焰喷涂和冷喷涂制备的银涂层的磨损机制主要为疲劳磨损。     

爆炸喷涂纳米WC-Co涂层的研究

为促进爆炸喷涂法替代常规喷涂工艺在工业上的应用,采用爆炸喷涂法制备了纳米和普通WC-12Co涂层.采用金相显微镜、扫描电镜分析比较了两种涂层的显微组织,用显微硬度计和磨料磨损试验机测试了两种涂层的显微硬度及耐磨料磨损性能,并利用扫描电镜对磨损形貌进行了分析.结果显示,纳米涂层具有比普通涂层更高的致密度和显微硬度,纳米涂层中WC颗粒的分布更均匀;纳米涂层的磨损机理为微观切削机制,其耐磨料磨损性能比普通涂层差.     

滚动接触条件下铁基涂层的疲劳磨损寿命实验研究

利用超音速等离子喷涂技术在45钢表面制备了铁基合金涂层,利用球盘式疲劳磨损实验机评价了铁基涂层在两种载荷条件下的疲劳磨损性能,利用两参数Weibull分布表征了涂层的疲劳寿命,采用扫描电子显微镜(SEM)分析了涂层的微观结构和失效形貌,利用有限元方法研究了涂层内部应力分布.实验结果表明,载荷条件可以显著地影响涂层的寿命和失效形貌,高载下涂层的寿命明显降低;随着载荷的增加,主要失效形式由表面磨损失效转换成剥层失效,其中表面磨损是由于粗糙接触引起,而剥层则与应力分布机制有关.     

等离子喷涂纳米结构与传统结构热障涂层的残余应力对比研究

热障涂层的残余应力是影响其服役寿研究不多.在45钢基体上,用超音速火焰喷涂NiCocrAlY打底层,再用大气等离子喷涂ZrO2-8%(质量分数)Y2O3(8YSZ)工作层,制备了纳米结构与传统结构2种类型的热障涂层(TBC).采用SEM、XRD对这2种涂层的粉末及涂层进行了组织结构分析,用纳米压痕仪测得了2种涂层的弹性模量.用X射线衍射应力测试仪测得了2种涂层的表层残余应力.结果表明:喷涂工艺参数相同条件下,对于打底层及工作层的厚度均相同的2种涂层,纳米结构热障涂层的表层残余应力比传统结构热障涂层约低24.7%;相同打底层的纳米结构热障涂层表层残余应力随着陶瓷层厚度增加而增加,陶瓷层厚度在240 um以下时,表层为残余压应力;厚度超过300 um时,表层为残余拉应力.最后提出了相应的物理力学模型.     

反应等离子喷涂TiC/Fe涂层的摩擦磨损性能研究

采用等离子喷涂前驱体热分解技术制备的Fe-Ti-C系反应热喷涂粉末,在低碳钢基体上沉积TiC/Fe金属陶瓷复合涂层.利用SEM和X射线衍射仪对涂层的显微组织结构、磨损表面及其相组成进行分析;采用SRV型往复式摩擦磨损试验机评价喷涂涂层的摩擦磨损性能.结果表明: TiC理论含量为53%(质量分数)TiC/Fe金属陶瓷涂层的耐磨粒磨损性能较好,相比基体提高了约25倍;反应等离子喷涂TiC/Fe陶瓷涂层的磨损机制主要为粘着磨损和轻微的剥落.     

电热爆炸喷涂层的纳米力学性能研究

采用英国Micro Materials公司生产的Nano Test 600型纳米多功能测试仪,对电热爆炸喷涂方法制备的FeAl、FeCrAl、FeCrAlRE 3种电爆喷涂层,进行力学性能测试,通过3种涂层加卸载曲线的对比,以及每种涂层的硬度、弹性模量的测取,分析铁基3种电爆喷涂层的力学性能及涂层表面规律,从而优化电爆喷涂工艺参数.     

深冷处理粉末对冷喷涂层的沉积和磨损性能影响

对铁基非晶合金粉末进行循环深冷处理增强其塑性变形能力,采用冷喷涂技术在AZ31B镁合金、6061铝合金以及Q235碳钢等具有不同性能的基体材料表面制备非晶涂层,研究深冷处理铁基非晶粉末在不同基体表面的沉积行为、涂层与基体间的界面结合状态以及涂层的摩擦磨损性能。结果表明,基体的硬度、导热系数和弹性模量会影响颗粒的应变条件、散热速率和回弹能量,进而影响涂层的变形状态、致密程度和沉积效率;深冷处理提高了非晶涂层的沉积效率,涂层的沉积厚度均大于原始非晶涂层。在摩擦磨损过程中,随着基体硬度的上升,基体及涂层的摩擦系数增大,磨损率降低。与基体相比,铁基非晶合金颗粒有效抑制了磨球的切削作用,原始非晶涂层的摩擦系数减小,磨损率降低;与原始非晶涂层相比,深冷处理非晶涂层更加致密,其摩擦系数曲线更加平稳,磨损率进一步降低。镁合金基体和非晶涂层的磨损机制都为磨粒磨损和氧化磨损;铝合金基体的磨损机制为粘着磨损和疲劳磨损以及氧化磨损,非晶涂层的磨损机制都为磨粒磨损和氧化磨损;碳钢基体和非晶涂层的磨损机制都为疲劳磨损和氧化磨损。     

沉积温度对磁控溅射制备V-Al-Si-N硬质涂层结构及性能的影响

采用磁控溅射工艺制备了不同沉积温度的V-Al-Si-N涂层,利用X射线衍射、扫描电镜、纳米压痕仪和摩擦磨损试验机对涂层的结构和性能进行了分析。研究结果表明:室温下制备的涂层生长缺陷较多,残余应力较大。适当提高沉积温度至300℃,涂层的晶体结晶性得到提高,柱状晶粗大贯穿整个膜厚,晶粒尺寸变大;继续提高沉积温度至500℃时,涂层呈(200)择优取向,晶粒尺寸变小,涂层致密度提高。随着沉积温度的提高,涂层的硬度略有下降,但是涂层的摩擦学性能得到大幅度提升。500℃制备涂层的硬度为29.7 GPa,磨损率达到6.1×10-17m3/Nm,比室温制备的涂层的磨损率降低了两个数量级。     

强流脉冲电子束作用下TiCN涂层微观结构变化与性能研究北大核心CSCD

采用化学气相沉积(CVD)技术在硬质合金基体表面制备TiCN涂层,随后利用强流脉冲电子束(HCPEB)对TiCN涂层表面进行辐照处理。通过X射线衍射仪(XRD)、扫描电子显微镜(SEM)等仪器观察了HCPEB辐照前后TiCN涂层的微观结构变化,并对比分析了其显微硬度和耐磨性能。结果表明:HCPEB辐照前后TiCN涂层的相组成保持不变,但相衍射峰的位置发生偏移且有所宽化,表明涂层晶粒细化,同时涂层内部应力状态发生改变;辐照后涂层表面粗大的晶粒消失,涂层变得光滑平整;随着辐照次数的增加,涂层的厚度逐渐减小。显微硬度和摩擦磨损试验结果表明,HCPEB辐照显著增加了TiCN涂层的表面显微硬度,其耐磨性能得到显著提升。涂层表面粗糙颗粒的消除、涂层晶粒细化、高密度晶体缺陷的形成以及涂层内部残余应力的改变是HCPEB辐照TiCN涂层性能改善的主要原因。     

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...     

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.     

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.     

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.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.