Effects of electrical discharge surface modification of superalloy Haynes 230 with aluminum and molybdenum on oxidation behavior

The effects of the electrical discharge alloying (EDA) process on improving the high temperature oxidation resistance of the Ni-based superalloy Haynes 230 have been investigated. The 85 at.% Al and 15 at.% Mo composite electrode provided the surface alloying materials. An Al-rich layer is produced on the surface of the EDA specimen alloyed with positive electrode polarity, whereas, many discontinuous piled layers are attached to the surface of the EDA superalloy when negative electrode polarity is selected. The oxidation resistance of the specimen alloyed with positive electrode polarity is better than that of the unalloyed superalloy, and the effective temperature of oxidation resistance of the alloyed layer can be achieved to 1100 °C. Conversely, the oxidation resistance of the other EDA specimen alloyed with negative electrode polarity is even worse than that of the unalloyed superalloy.     

Effects of pH value of reaction solution on structure and electrochemical performance of calcium-containing active material of secondary zinc electrodes

The calcium-containing active material of secondary alkaline zinc electrodes was prepared by a chemical coprecipitation method and characterized by scanning electron microscopy(SEM) and X-ray diffractometry(XRD).Their electrochemical performance was tested by the Galvanstatic charge-discharge method. The experimental results show that the sample synthesized at pH: 11. 15 has a typical calcium zincate crystal. The zinc electrode using this sample as active material shows higher discharge capacity, more negative discharge plateau potential and longer cycle lifetime.     

Al-5%Ti-0.25%C细化剂合金微观组织与细化性能

采用液固反应合成技术,通过铝熔体润湿经活化与助熔处理的无定型石墨的方法,成功地制备了Al-5%Ti-0.25%C细化剂合金,并通过透射电镜(TEM)、光学显微镜(OM)、X射线衍射(XRD)和能谱分析(EDS)等手段,研究了该合金的组织特性与细化性能.结果表明:Al-5%Ti-0.25%C细化剂合金组织由Al基体、针状及片状TiAl3相和TiC粒子团簇组成,且部分TiC粒子与α-Al基体存在晶体取向关系;Al-5%Ti-0.25%C细化剂具有优异的细化a-Al晶粒的性能,细化接触时间和衰减时间分别为2.5min和110min.     

高温作用后C20混凝土强度的无损检测

C20混凝土试块在450℃高温下持续不同时间后自然冷却，再对其进行超声、回弹综合法及标准抗压强度试验，以探讨同一高温不同时间作用后混凝土强度的变化规律，分析无损检测与标准抗压强度试验之间的关系。     

金属型铸造高铬铸铁Cr20组织及性能的研究

研究了金属型铸造高铬铸铁Cr20的铸态组织和性能,以及主要合金元素对性能的影响。结果表明,用金属型铸造的高铬铸铁Cr20的铸态组织为奥氏体基体,共晶碳化物为孤立的块状分布,具有较高的硬度和一定的韧性,并且还可以降低合金元素Mo和Ni的加入量。对于不能通过常规热处理进行淬火硬化的高铬铸铁件,可用金属型铸造来满足在铸态下使用的要求。     

高效催化3α-高托品烷肟加氢的Rh-Pd/C催化剂

采用甲醛还原-活性炭负载法制备了5%Rh/C、5%Pd/C和3%Rh-2%Pd/C三种催化剂,用X射线衍射(XRD)、电子显微镜(SEM和TEM)以及X射线光电子能谱(XPS)进行表征,对比其在合成3α-高托品烷胺中的催化性能。表征结果表明,在载体表面Rh-Pd二元合金颗粒粒径最小,分散性最好,可能形成了"网桥式"Rh-O-Pd结构。催化性能对比表明,3%Rh-2%Pd/C具有最佳催化性能,在25h内可以将99%以上的原料转化,目标产物产率大于96%,且补加20%新催化剂后可循环使用3次,可降低3α-高托品烷胺生产成本。     

PVD TBC experience on GE aircraft engines

The higher performance levels of modern gas turbine engines present significant challenges in the reli-ability of materials in the turbine. The increased engine temperatures required to achieve the higher per-formance levels reduce the strength of the materials used in the turbine sections of the engine. Various forms of thermal barrier coatings have been used for many years to increase the reliability of gas turbine engine components. Recent experience with the physical vapor deposition process using ceramic material has demonstrated success in extending the service life of turbine blades and nozzles. Engine test results of turbine components with a 125 μm (0.005 in.) PVD TBC have demonstrated component operating tem-peratures of 56 to 83 °C (100 to 150 °F) lower than non-PVD TBC components. Engine testing has also revealed that TBCs are susceptible to high angle particle impact damage. Sand particles and other engine debris impact the TBC surface at the leading edge of airfoils and fracture the PVD columns. As the impacting continues, the TBC erodes in local areas. Analysis of the eroded areas has shown a slight increase in temperature over a fully coated area ; however, a significant temperature reduc-tion was realized over an airfoil without TBC.     

Technique of pulse electrochemical finishing in molds and dies

Surface finishing is one of the most important processes in mould and die making. This process is necessary not only for smoothing the surface of die or mould, but also for removing the surface layer, which has been damaged by the preceding machining process and finally improve the performances and lifetime of moulds to a large extent. It has been reported that between 30% and 40% of the total time required to manufacture a die or mold is spent on finishing operations, most of which are performed by skilled workers employing traditional techniques. At present, key problems in mould and die finishing technology can improve the finishing efficiency, consistency and quality at reduced costs. A new and high efficiency unconventional finishing technology, pulse electrochemical finishing was introduced. Experiments were done in neutral nitrate electrolytes. The influence of electrolyte composition, intereletrode gap, finishing time, flow quality, current density, compositions of steel materials and pulse parameters on the resulting surface finishing was investigated. Results indicate that pulse parameters have important influence on operations finishing and the proper selection of pulse parameters can lead to both good smoothing efficiency and surface quality at low costs.     

提高18Mn—18Cr—N扩环钢中氮含量及收得率的研究

护环作为发电机一个最关键的零件，由于其所起的作用及受力状态决定了要求超高的强度、良好的塑韧性、无磁性及优秀的抗应力腐蚀的能力，为了提高制造18Mn-18Cr-n护环的强度等级，经分析认为提高护环钢中的氮含量是一个关键的因素，在对影响18Mn-18Cr-N钢中氮含量的因素进行分析研究及实验室小感应炉的模拟实验的基础上，编制出冶炼工艺，并在电炉上进行了6炉次的实践，钢中的氮含量达到了0.69%，氮的收得率最高达到71%，大大高于常规工艺方法的水平，达到了日本制钢所室兰工厂该钢种的氮含量水平。     

方波信号发生器及场效应管驱动器

本文介绍方波信号发生器及场效应管驱动器的原理与设计。实验证明,设计的方波信号发生器与场效应管驱动器工作稳定可靠,所研制的方波交流高频弧焊电源已成功地对薄钢板进行了焊接。