氮化钛涂层界面结构的电镜研究

用透射电镜研究了空心阴极离子镀氮化钛涂层。得到了涂层中α-Fe—FeTi、FeTi—αTi、αTi—Ti_2N、Ti_2N—TiN等界面的结晶学取向关系。在上述结果基础上,对界面原子结构图提出了假设,并对界面的形成机理进行了讨论。     

Ti811表面单道与多道TC4激光熔覆层微观组织对比

按照CFM发动机维修手册的修复建议,在Ti811钛合金表面,利用同步送粉激光熔覆技术,制备了单道与多道搭接TC4激光熔覆层。利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)和能谱分析仪(EDS)等分析了涂层组织和相组成,利用显微硬度计测试了涂层的显微硬度。结果表明,单道涂层微观组织呈现魏氏体结构,由α-Ti组成的晶界中分布大量的针状马氏体α′和残留β′-Ti,涂层中弥散分布着10—150nm的纳米Ti_3Al;多道搭接涂层由基底α-Ti和均匀分布的Ti_3Al组成;单道涂层和多道搭接涂层的显微硬度相比基底都有所提高,单道涂层显微硬度最高为485HV_(0.5),多道搭接涂层显微硬度最高为510HV_(0.5)。     

高速钢刀具激光熔覆AlTiN/NiCoCr涂层的组织及性能分析

为了提高高速钢刀具的综合性能,通过激光熔覆的方式在其表面制备AlTiN/NiCoCr涂层,通过实验测试的方式表征了该涂层的组织结构与各物相成分,并测定了其界面结合性能。研究结果表明:激光熔覆AlTiN/NiCoCr涂层形成致密组织,各层间形成紧密结合状态,陶瓷层厚度接近146μm,形成200μm左右粘结层。在陶瓷层内形成了大量无序排列的等轴晶,获得更高强度的陶瓷层。涂层中主要存在α-Al_2O_3,还有部分Al_2Ti_5N与Rutile-TiN。采用激光熔覆工艺有效降低了界面的空隙比例,获得更加致密的界面组织。陶瓷相内含有Al、N、Ti三种元素,在微孔粘结层内存在Co与Ni。AlTiN/NiCoCr涂层获得了比NiCoCr涂层更高结合力和更小的残余应力。试样发生了台阶断裂,形成了凹凸变化的表面。AlTiN/NiCoCr涂层形成更加平整断裂界面,在断裂面区域形成了众多微孔。     

Fe/Al2O3陶瓷梯度涂层的结合性能

以FeAl和FeAlNi两种混合粉体作为底层材料,将喷涂法和溶胶-凝胶相结合制备了Fe/Al_2O_3梯度涂层,分析了其与钢基表面的结合性能。结果表明:当烧结温度为1220℃时,两种过渡底层Fe/Al_2O_3陶瓷梯度涂层的界面结合强度分别达到21.2 MPa和25.3 MPa,涂层的物相组成分别为α-Al_2O_3、AlFeO_3、Al_2Fe_2O_6、Al_3Fe_5O_(12)和α-Al_2O_3、AlFeO_3、NiFe_2O_4等。与FeAl相比,以FeAlNi作为过渡底层制备的Fe/Al_2O_3梯度涂层材料结构致密度高、没有明显孔洞与宏观界面,且有树枝状组织生成,有利于涂层结合性能的提高。     

Ti-N薄膜与钢基体界面显微结构的透射电镜研究

用透射电镜分别研究了空心阴极离子镀加Ti底层和不加Ti底层的Ti-N薄膜与不锈钢和高速钢基体之间界面的显微结构。在较厚Ti底层与不锈钢基体间的界面上有厚约20nm的FeTi界面层,Ti底层由具有[0001]取向的α-Ti相组成,TeTi相有[311]、[310]、[321]、[320]等几种择优取向。此外,较薄Ti底层与不锈钢基体间的界面比较光滑,界面层很薄。在基体温度为500℃时镀得的加Ti底层的Ti-N膜与高速钢基体的界面上,也观察到了Ti底层。它由细小的α-Ti晶粒组成,其中弥散分布着一些TiC的微小晶粒。在邻近膜/基界面的基体内断续分布着一些FeTi相的晶粒。在不加Ti底层的Ti-N膜与高速钢基体的界面上,观察到了TiN晶粒在基体中的碳化物MC(VC)上的外延生长,它们之间存在[310]_(vc)∥[100]_(TiN)的晶体学取向关系。与此类似,在高速钢中马氏体的晶粒上也外延生长出了TiN晶粒。在M_6C上生长的TiN初始晶粒很小,晶界不清晰。TiN与高速钢中碳化物和马氏体间的界面均较光滑,未观察到界面相。     

Ti811表面激光熔覆原位合成TiC-TiB2复合Ti基涂层的微观组织分析

在Ti811钛合金表面利用同步送粉激光熔覆技术,制备了TC4+Ni45多道搭接激光熔覆层。利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、能谱分析仪(EDS)等分析了涂层组织和相组成,利用显微硬度计测试了涂层的显微硬度。结果表明,涂层微观组织中均匀分布的析出相主要包括基底α-Ti、金属间化合物Ti_2Ni、增强相TiB_2和增强相TiC。其中,TiC在TiB_2表面异质形核,形成了TiC+TiB_2的复合相结构;同时,纳米TiC颗粒在涂层基体中弥散分布。由于涂层中TiC与TiB_2的共同作用,涂层的显微硬度与基底相比有了显著提高,最高硬度为770HV0.5左右,约为基底硬度的2倍。     

固体润滑剂WS2含量对钛合金表面激光熔覆NiCr/Cr3C2-WS2层组构及性能的影响

为拓宽钛合金表面耐磨自润滑复合涂层的研究领域,采用10 kW CO2激光器,在Ti-6Al-4V钛合金表面熔覆制备了4种不同WS2含量(0,10％,20％,30％)的NiCr/Cr3C2-WS2层.利用扫描电镜(SEM)、能谱分析仪(EDS)和X射线衍射仪(XRD)等分析了涂层组织、相组成以及磨损形貌,利用MH-5半自动显微硬度计和HT-1000型球-盘式高温摩擦磨损试验机测试了涂层的硬度和摩擦磨损性能,对比研究了4种NiCr/Cr3C2-WS2熔覆层的微观组织和在室温、载荷为6N条件下的摩擦学性能.结果表明:未添加WS2熔覆层的组织主要是由γ-NiCrAlTi,TiC和α-Ti相组成,添加WS2熔覆层的组织主要是由γ-NiCrAlTi,TiC,TiWC2,α-Ti,Ti2CS和CrS相组成;未添加WS2的熔覆层的平均显微硬度最高,达到1 149 HV2N,是钛合金基体显微硬度的3.2倍.添加WS2固体自润滑剂改善了熔覆层摩擦学性能,其中添加30％ WS2的熔覆层摩擦学性能最佳.     

Nb丝增强Ti-48Al-2Cr基复合材料制备及复合机制

采用真空水冷铜坩埚感应熔炼炉及石墨型离心铸造工艺,制备了Nb丝连续增强Ti-48Al-2Cr基复合材料.测试了该复合材料的显微结构、界面结合形貌与力学性能.研究结果表明:Nb丝与基体结合良好,界面处元素发生了相互扩散,界面层组织为Ti2 AlNb相,α2-Ti3 Al相及γ-TiAl相,硬度呈梯度分布,在界面层处最高为...     

热处理对激光熔覆钛基复合涂层组织和微动磨损性能的影响

为研究不同温度热处理对激光熔覆钛基复合涂层组织和微动磨损性能的影响,采用激光熔覆技术在TA2钛合金表面制备40%Ti-25.2%TiC-34.8%WS_2(质量分数)复合涂层,将涂层分别置于300,500℃和700℃真空中保温1h,分析热处理前后涂层的显微组织和微动磨损耐磨性能。结果表明:未经过热处理涂层及经过不同温度热处理涂层的主要物相均为α-Ti,(Ti,W)C_(1-x),TiC,Ti_2SC和TiS。未热处理及经过300,500℃和700℃热处理1h涂层的显微硬度分别为1049.8,980.7,1143.3HV_(0.5)和1190.7HV_(0.5)。经过700℃热处理1h涂层表现出优异的微动磨损性能,磨损机理为黏着磨损和磨粒磨损。     

TiH2粉末烧结研究进展

目的 研究烧结温度、升温速率、压制压力分别对TiH2粉末压坯脱氢相演变过程以及显微组织的影响规律.方法 采用氢化钛(TiH2)粉末为原料,经过压制和真空烧结制备粉末冶金Ti材料,结合原位中子粉末衍射、差示扫描量热法等技术,表征TiH2粉末压坯在烧结过程中的显微形貌及相变过程.结果 在真空烧结条件下,TiH2粉末压坯的脱氢相变反应过程为:δ-Ti(H)→δ-Ti(H)+α-Ti(H)→δ-Ti(H)+β-Ti(H)+α-Ti(H)→β-Ti(H)+α-Ti(H)+α-Ti→α-Ti;升温速率的增加会延缓TiH2的相变过程及动力学.结论 TiH2粉末坯体的压制压力越大,烧结时TiH2脱氢并释放氢气导致坯体内部的气压越高,从而导致TiH2坯体的烧结致密化程度较低.     

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.     

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.     

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.     

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.……     

Analysis of marine hydrobiont lipid extracts as possible cryoprotective agents

We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes.     

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.