铌合金表面渗镀复合涂层及其抗氧化研究

利用包埋渗结合化学镀技术在铌合金表面制备了复合涂层,研究了涂层在退火过程中的元素扩散行为及涂层的高温抗氧化性能。结果表明:复合涂层以晶态Ni和Al_3Nb相为主;退火过程中渗层中的Al元素向外扩散,涂层转变为晶态,形成了Ni Al_3、Al_3Nb、Ni Al相。对退火前后的涂层进行1000℃恒温氧化实验,20 h后沉积态涂层的增重为7.7 mg/cm~2,表面主要含Ni O、Al_2O_3、Ni Al相;退火态涂层样品的增重为4.9 mg/cm~2,表面生成了Al_2O_3、NiNb_2O_6、NiAl_2O_4等相。氧化后涂层与基体结合良好。退火态涂层表面由于富Al元素,氧化后形成较多的Al_2O_3,比沉积态的涂层能更有效地减缓氧化进程,提高铌合金的抗氧化性。     

钛合金表面梯度Al2O3陶瓷涂层的高温抗氧化性能

钛合金应用广泛,但在高温环境中极易被氧化,降低其力学性能及寿命。利用溶胶-凝胶法在TC11钛合金上制备梯度层(ZrO_2+Al_2O_3)+表层(Al_2O_3)的复合梯度涂层,提高其高温抗氧化能力。将复合梯度涂层、单层氧化铝涂层以及基体在700℃进行100h的高温氧化,利用氧化增重数据拟合得到梯度涂层的氧化速率为0.015mg~2/(cm4·h),氧化指数为2.137,并结合氧化后EDS成分分布,发现复合梯度涂层可以提高基体的高温抗氧化性能。同时利用700℃热震实验比较了复合梯度氧化铝涂层试样和单层氧化铝陶瓷试样的热震次数,梯度层(ZrO2+Al_2O_3)的存在缓解了基体与氧化铝陶瓷涂层之间热膨胀系数不匹配而导致的易剥落的问题,延长了涂层寿命,进一步提高了基体的高温抗氧化能力。     

一种新型钴基高温合金在900℃熔融NaCl中的热腐蚀行为

采用浸盐法研究一种新型钴基高温合金在900℃熔融NaCl中的热腐蚀行为。结果表明:腐蚀初期合金发生选择性氧化,在表面生成Al_2O_3,Cr_2O_3和少量的TiO_2。随着腐蚀时间的延长,熔融NaCl开始侵蚀表面保护性Cr_2O_3和Al_2O_3,使腐蚀性介质与基体逐渐接触,加速合金腐蚀。随着腐蚀的进行,合金内腐蚀层生成棒状Al_2O_3。由于基体中Al的消耗,棒状Al_2O_3周围易生成Co3W。Co3W与棒状Al_2O_3的相界面形成氧扩散的快速通道,导致80h后合金热腐蚀加剧。     

溅射Ni_3Al微晶涂层的抗氧化性能

研究了铸态 Ni_3Al 合金及其微晶溅射涂层在1000—1100℃下等温氧化性能及1000℃下的循环氧化性能。结果表明:铸态 Ni_3Al 合金在氧化过程中形成 Al_2O_3,NiO 和 NiAl_2O_4 的复杂氧化膜;微晶 Ni_3Al涂层在氧化过程中形成α—Al_2O_3和 NiAl_2O_4尖晶石,不含 NiO,这种氧化膜的保护作用比含 NiO 的氧化膜的保护作用好,使得其氧化增重比铸态合金小约1半。此外铸态 Ni_3Al 合金在氧化过程中沿粗大晶界发生严重的内氧化,且表面氧化膜较脆易发生剥落;微晶 Ni_3Al 涂层可以消除沿晶界的内氧化,氧化膜与基体粘附良好,未发现剥落现象。微晶化大大提高了 Ni_3Al 合金的抗氧化性能。     

等离子喷涂MCrAlY涂层的高温氧化性能

采用大气等离子喷涂(APS)设备制备了两种含有不同氧化物(Cr_2O_3和Al_2O_3)陶瓷成分的MCrAlY (MCrAlY-CrO和MCrAlY-AlO)涂层,并使用光学显微镜、扫描电镜、X射线衍射仪及显微硬度计等仪器设备,分析了涂层的微观形貌、物相组成及硬度,并对两种涂层进行了高温氧化试验。结果表明:大气等离子喷涂得到的两种MCrAlY涂层中含有Cr_2O_3,Ni_3Al,Al_2O_3和部分非晶相,其结构为平行于涂层与基体结合面的层状结构,涂层中含有半熔化颗粒、微裂纹及灰黑色氧化物;在高温氧化试验中,MCrAlY-CrO涂层与MCrAlY-AlO涂层均表现出较好的耐高温氧化性能,这是因为在高温状态下涂层表面分别生成了铬和铝的氧化产物,对涂层起到了保护作用。     

一种新型Ni-Fe-Cr基合金在模拟锅炉烟气中的腐蚀行为研究

应用X射线衍射仪、扫描电子显微镜、能谱仪等分析方法研究一种新型Ni-Fe-Cr基高温合金在700℃/750℃煤灰/烟气中的腐蚀行为。结果表明:750℃的腐蚀速率明显高于700℃,其腐蚀层的厚度由700℃的3μm增加到20μm。腐蚀1 000h后,SEM观察到Ni-Fe-Cr高温合金在700℃下表面有少量"瘤状"凸起产物,XRD结合EDS表明其腐蚀产物由表向里依次是结构疏松的NiO、Fe_2O_3和Fe3O4,内层为相对致密的Cr_2O_3、Al_2O_3和TiO2,基体和腐蚀层界面靠近基体一侧是多孔的硫化物。提高腐蚀温度到750℃表面出现更多凸起,并且出现了破裂。Cr_2O_3保护性氧化膜局部开裂或者剥落而形成"瘤状"凸起产物。氧化膜生长过程中的内应力以及温度降低产生的热应力共同作用,导致氧化膜开裂甚至与基体剥离。温度升高同样加剧熔融盐破坏氧化膜从而加快腐蚀进程。     

粉末增塑挤压制备Al_2O_3/Fe复合型蜂窝材料的组织与性能

为制备性能优良的Al_2O_3/Fe复合型蜂窝材料,首先以316L合金粉末、Al_2O_3粉末和黏结剂为原料,通过粉末增塑挤压及在1 200℃氩气气氛中烧结2h获得了Al_2O_3/Fe复合型蜂窝材料;然后,借助SEM、XRD及万能试验机研究了添加Al_2O_3对Al_2O_3/Fe复合型蜂窝材料组织与性能的影响。结果表明:金属粉末颗粒在烧结过程中结合形成γ-Fe基体网状组织,表面有呈多边形几何状形态的Cr_2O_3形成;添加少量的Al_2O_3可以抑制Cr从基体中析出,降低表面Cr_2O_3的含量,使金属颗粒烧结结合更为紧密,组织表面更加光滑;随着Al_2O_3含量的增加,蜂窝材料表面与催化活性涂层的结合能力增强,复合型蜂窝材料的抗压强度先升高后降低;在Al_2O_3含量为5.0wt%时,抗压强度达26 MPa。所得结论表明5.0wt%Al_2O_3/Fe复合型蜂窝材料力学性能最佳,表面涂覆性能优良。     

NiCoCrAlYHf涂层材料的1200℃高温氧化行为

本文研究了采用精密铸造成型技术制备的NiCoCrAlYHf涂层材料在1200℃高温氧化行为。对于涂层材料试样进行了1200℃循环抗氧化实验,来评价其抗氧化性能,通过扫描电镜分析氧化后的试样显微形貌,用X-射线衍射仪分析涂层材料的相结构,通过氧化速率对涂层材料抗氧化性能进行表征。试验结果表明:NiCoCrAlYHf涂层材料在1200℃的循环氧化寿命大于300h;氧化后涂层材料表面形成了氧化膜以Al_2O_3为主,相结构主要由Al_2O_3和Ni_3Al为主。     

Ti6Al4V合金激光原位合成自润滑复合涂层高温摩擦学性能

为提高Ti6Al4V合金的高温摩擦学性能,采用激光熔覆技术在其表面原位合成多相混杂金属基高温自润滑耐磨复合涂层,熔覆粉末的成分为Ni60-16.8%TiC-23.2%WS_2(质量分数,下同),系统地研究复合涂层的显微组织、物相结构及其在20,300,600,800℃下的摩擦学性能和相关磨损机理。结果表明:复合涂层的显微硬度(701.88HV_0.5)约为基体(350 HV_0.5)的2倍;由于原位合成固体润滑相(Ti_2SC/TiS/NiS/TiO/TiO_2/NiCr_2O_4/Cr_2O_3)和硬质相(W,Ti)C_1-x/TiC/Cr_7C_3的协同作用,复合涂层的耐磨减摩性能明显优于基体。随着温度升高,涂层和基体的摩擦因数和磨损率均呈下降趋势,在800℃时复合涂层和基体的摩擦因数分别为0.32和0.43,磨损率分别为1.80×10^-4,2.92×10^-5mm/Nm。在800℃下塑性变形、分层和氧化磨损为基体主要磨损机理,复合涂层以氧化磨损和轻微的黏着磨损为主。     

溅射Ni11Co26Cr6Al0.5Y涂层对镍基合金在1000 ℃氧化行为的影响

通过对有/无Ni11Co26Cr6Al0.5Y涂层镍基合金在1000℃进行氧化动力学曲线测定,及组织结构观察,研究了Ni11Co26Cr6Al0.5Y涂层对镍基合金高温氧化行为的影响。结果表明:高温氧化期间,合金发生外氧化和内氧化,外氧化层由NiO、NiCrO_4、CoWO_4构成,中间氧化物由TiO_2、Al_2O_3、NiWO_4构成,中间层氧化物层抑制了基体中Al元素向外扩散,形成平直连续的Al_2O_3内氧化物层;合金氧化动力学曲线呈现起伏波动的特征。镍基合金经溅射Ni11Co26Cr6Al0.5Y涂层,可有效改善合金的抗氧化性能;涂层的氧化动力学曲线仅在氧化初期有轻微增重而后趋于平稳,遵循抛物线规律,其形成的Al_2O_3氧化膜未发生明显剥落,仅在涂层内及近涂层/基体界面区域存在少量Al_2O_3内氧化物。     

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.……     

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.     

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.     

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.     

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.