Ti6Al4V合金激光熔覆γ-NiCrAlTi/TiC复合层的组织与摩擦学性能

为提高Ti6Al4V合金的摩擦学性能,以NiCr-Cr₃C₂金属陶瓷粉末为涂覆材料,采用激光熔覆技术在Ti6Al4V表面制备以TiC为增强相、γ-NiCrAlTi固溶体为增韧相的熔覆层。采用X射线衍射仪（XRD）、扫描电镜（SEM）、能谱仪（EDS）分析了熔覆层的物相组成及显微组织,测试了熔覆层沿层深方向的硬度分布,分别在室温（24℃）,300,600℃测试了熔覆层和Ti6Al4V合金基体的干滑动磨损性能。结果表明:熔覆层的平均硬度约1 100HV_{2 N},约为基体的3倍;室温时,由于高硬度增强相TiC和增韧相γ-NiCrAlTi固溶体的综合效应,激光熔覆γ-NiCrAlTi/TiC复合层的摩擦系数和磨损率比Ti6Al4V合金基体的显著降低,熔覆层具有较好的耐磨减摩性能,磨损机理主要为黏着磨损;300,600℃时,熔覆层被氧化,耐磨性减弱,磨损机理主要为黏着磨损和塑性变形。     

钛合金表面激光熔覆Ti/Al/B4C/C涂层组织与性能分析

针对钛合金硬度低和耐磨性差的特点,采用激光熔覆技术在TC4钛合金表面制备Ti/Al/B4C/C熔覆层,利用XRD、SEM、EDS探究熔覆层微观组织,并测试熔覆层对TC4钛合金表面硬度及耐磨性能的影响。结果表明:Ti/Al/B4C/C熔覆层中由于形成Ti B、Ti B2、Ti C等硬质陶瓷相及Ti-Al系金属间化合物和Ti3Al C相,相比于基体具有高的硬度和优异的耐磨性。熔覆层硬度在1 100～1 720 HV之间,较基体提升了2～3倍,其体积磨损率约为(2.29～4.18)×10-6mm3/(N·mm),较基体降低了14%～53%,其中以Ti∶Al∶B4C∶C=57∶20∶18∶5(质量比)混合粉末形成的熔覆层性能最好。     

激光熔覆制备原位自生TiC增强Ni3（Si,Ti）复合涂层研究

运用激光熔覆技术修复受损的烟汽轮机叶片,在GH864镍基合金表面制备原位自生TiC颗粒增强Ni3(Si,Ti)金属间化合物复合涂层.利用扫描电镜、能谱分析仪、X射线衍射仪及显微硬度计研究了(Ti+C)的加入量对熔覆层组织及硬度的影响.研究表明:在优化的工艺参数下可获得宏观质量完好,无裂纹、气孔等缺陷,且与基体呈冶金结合的激光熔覆层,熔覆层由Ni(Si)、Ni3(Si,Ti)和TiC组成;当合金粉末中(Ti+C)的加入量为20%时熔覆层的硬度最高可达780Hv,是基体材料的2.4倍.     

激光熔覆原位生成Nb_2(C,N)及V_8C_7陶瓷粒子增强铁基金属涂层

采用5kW CO2激光设备,在42CrMo基体上制备出原位合成Nb2(C,N)及V8C7颗粒增强的铁基复合涂层,研究了熔覆层的组织及性能。结果表明:激光熔覆层主要组成相为α-Fe相、γ-Fe相、Nb2(C,N)及V8C7;增强相颗粒弥散分布在铁基复合涂层中,与母材相比,其磨损失重约为母材的1/8,显著提高了熔覆层的硬度和耐磨性。进一步的抗氧化性实验结果表明,氧化层结构连续致密,与42CrMo基体相比,在750℃/120h恒温氧化后的氧化层的厚度约为基体氧化层厚度的1/8。     

钛合金表面激光熔覆Ti/Ni+ZrO_2涂层的组织与性能

为提高TA15钛合金的表面硬度和耐磨性,采用激光熔覆方法在钛合金表面制备了Ti/Ni+5%ZrO_2涂层(质量分数),并对其组织和性能进行了研究。结果表明:熔覆层与基体结合良好;熔覆层中除了有Ti2Ni和TiNi金属间化合物之外还有少量的单斜相氧化锆(m-ZrO_2)和四方相氧化锆(t-ZrO_2);熔覆层中主要生成相TiNi和Ti2Ni可以极大地提高熔覆层的耐磨性和硬度,ZrO_2相在提高熔覆层韧性的同时,进一步提高了熔覆层的耐磨性和硬度。     

Ti6Al4V表面激光熔覆纯Cr粉热力学分析

为研究在激光作用下元素之间的扩散及作用机理,采用激光熔覆方法在Ti6Al4V表面熔覆纯Cr粉,利用热力学相图分析软件Thermo-Calc对Cr-Ti-Al-V四元体系进行平衡相图计算分析,利用DICTRA软件模拟合金体系的元素在Ti6Al4V基体中扩散分布情况。X射线衍射图谱表明熔覆层主要由α-Ti、Laves相Cr2Ti及亚稳态Cr1.97Ti1.07组成;扫描电镜实验结果显示熔覆层主要由片状、树枝状及细小针状组织组成。熔覆层元素体系中主要为Cr、Ti元素在不断相互扩散,Al元素扩散缓慢,V含量基本没有变化,整个体系中主要参与反应的是Cr与Ti元素。     

激光熔覆Co1.5CrFeNi1.5Ti0.75Nbx高熵合金的组织和性能研究

目的 研究Nb含量对高熵合金Co1.5CrFeNi1.5Ti0.75Nbx熔覆层组织和性能的影响.方法 在H13钢表面制备了Co1.5CrFeNi1.5Ti0.75Nbx(x=0.25,0.50,0.75,1.00,原子数分数)高熵合金熔覆层,研究Nb含量对熔覆层的物相组织、微观结构、硬度和耐磨性的影响.结果 高熵合金熔覆层主要为BCC相、FCC相和Laves相的组织.在熔覆层中添加Nb,Laves相随之增加,组织的微观形貌发生变化.熔覆层的硬度远远高于H13钢(退火态),Co1.5CrFeNi1.5Ti0.75Nb0.5熔覆层的平均硬度最高,约为H13钢(退火态)的2.8倍.Co1.5CrFeNi1.5Ti0.75Nb0.5熔覆层的摩擦磨损失重最小,磨损程度更低,耐磨性更好.结论 Nb元素加入高熵合金体系会形成Laves相,Laves相能够提高高熵合金的力学性能.相关结果 对于高熵合金体系的研究具有一定意义,为高熵合金的成分设计和优化提供了必要的实验支持.     

利用JMatPro软件进行合金覆层成分设计及回火工艺制定

利用JMatPro软件对合金覆层进行计算,模拟分析了不同回火状态下合金覆层内部相组成成分的变化情况与碳化物颗粒的析出情况,预测了合金覆层的相关性能;采用微束等离子熔覆加工方法,在H13钢基体上熔覆制备了合金覆层,研究分析了合金覆层回火前后的组织形态、物相组成、元素分布和显微硬度变化。结果表明,对合金覆层进行200℃回火2 h,合金覆层内部组织结构、物相组成与回火前相比无明显变化,显微硬度也无明显变化(463 Hv_0.1);经400℃回火2 h后,合金覆层组织内部开始有少量MC型特殊碳化物析出,晶界周围逐渐呈现不连续的网状分布,一定程度上提升了覆层的显微硬度(512 Hv_0.1);经600℃回火2 h后,合金覆层组织内部析出大量MC、M2C型特殊碳化物,之前不连续的网状分布发展为连续、密集的蛛网状分布,合金覆层内部整体呈现出更为细小、均匀的组织形态,覆层硬度提升约25.88%,达到569 Hv_0.1。     

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.     

热处理对钛合金激光熔覆自润滑耐磨复合涂层组织和摩擦学性能的影响

为了进一步提高钛合金激光熔覆层的质量,以Ni Cr/Cr_3C_2-WS2复合粉末为原料,采用激光熔覆技术在Ti6Al4V(TC4)钛合金表面制备了自润滑耐磨复合涂层,并将复合涂层在600℃下保温1 h,采用扫描电镜、X射线衍射仪、摩擦磨损试验系统地分析了涂层热处理前后的组织、显微硬度和摩擦学性能的变化及其机理,研究了热处理对自润滑耐磨复合涂层性能的影响。结果表明:自润滑耐磨复合涂层的主要物相为韧性相Ni Ti2,增强相Cr_3C_2、Cr7C_3、Ti C以及润滑相Ti_2SC、Cr S;热处理1 h后涂层的显微硬度(928.8 HV5 N)相对于未热处理涂层(1 076.1HV5 N)略有下降;相对于未热处理涂层,热处理1 h后的涂层表现出良好的耐磨减摩性能,其磨损机理为磨粒磨损。     

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.