24D-450S电源装置的研制

介绍了为CPD15进口叉车配套的24D－450S电源装置的任务来源，主要技术要求，电池构思、基本结构、试制和试验简况及所达到的性能指标等。     

CeO₂改善低温渗铝涂层抗氧化性能的研究

在Ni基体上电沉积纯Ni镀层和Ni-CeO2复合镀层并对其进行620 °C低温渗铝,制备了无CeO2和CeO2改性的铝化物涂层。将以上两种涂层在1000 °C下氧化,研究CeO2颗粒的加入对氧化膜的生长速率和粘附性能的影响。结果表明,在δ-Ni2Al3涂层中加入纳米CeO2颗粒可以推迟一层完整α-Al2O3膜的形成时间,降低氧化膜的生长速率。此外,纳米CeO2颗粒的加入提高了氧化膜的粘附性,原因是与没有CeO2掺杂的涂层相比,CeO2改性铝化物涂层在氧化膜/涂层界面上形成的空洞尺寸较小。     

不锈钢表面渗铝并热氧化处理对氢渗透的影响

首先， 采用固体粉末包埋法在不锈钢表面渗铝.渗铝层表面是呈较粗大的结晶状致密组织，主要由F eAl相组成.渗层呈多层结构，分为外层（约25μm），过渡层（约5μm）和内层（约30μm），各亚层间及渗层与 基体间结合紧密，无裂缝.渗铝表层铝浓度较高，超过30 mass %.然后，采用热氧化的方法 ，使渗铝层发生选择性氧化，在表面生成了 一薄层均匀、致密的Al2O3膜.在900℃，2.0×10-2Pa氧气环境中氧化2小时 所生长的膜的厚度约为0.6 μm.将氧化后的样品放入超高真空吸放氢测试系统中进行渗氢 处理,再用前向弹性反冲（ERD）测定渗氢样品中氢的分布.结果表明：沿着膜 层深度方向，氢原子浓度急剧降低.在深度为0.2 μm处，原子浓度趋于平衡，原子百分比 浓度大约保持在0.007 at%左右，与不锈钢基体化学组成中氢原子含量相近，氢原子难以渗 透进去.这说明本研究制备的Al2O3膜层具有良好的防氢渗透效果.  〖HT5”H〗中图分类号：〖HT5”SS〗〓〓 〖     

45#钢Cr-N包埋共渗涂层的组织特征及形成机理

目的研究在45~#钢表面包埋共渗沉积Cr_2N涂层提高其耐蚀性的可行性。方法采用包渗法,对在1100℃下保温不同时间,得到不同时期的氮铬共渗涂层。利用扫描电镜及能谱仪、X射线衍射仪研究氮铬共渗层的微观组织及其生长机制,利用极化曲线评估涂层耐蚀性能。结果 45~#钢氮铬包埋共渗在保温4 h时可获得最佳涂层,涂层组织为Cr_2N层(约15μm)、Cr的沉积层(约10μm)、Cr的扩散层(约15μm)。Cr_2N层呈现强烈的(002)晶面择优取向;Cr沉积层为Fe-Cr合金及铬的碳化物相(Cr_7C_3,Cr_3C_2)。在模拟燃料电池腐蚀液中,45~#钢、45涂层样品、304不锈钢自腐蚀电位和自腐蚀电流分别为-0.521 V和230.63μA·cm~(-2),-0.448 V和10.89μA·cm~(-2),-0.299 V和5.26μA·cm~(-2)。当腐蚀电位高于0.3 V时,涂层样品会二次钝化,腐蚀电流低至1.43μA·cm~(-2)。结论沉积Cr_2N的45~#钢样品相对原样其耐蚀性有很大提高,并且当腐蚀电位达到0.3 V以上时,其耐蚀性能优于304不锈钢。     

ZrB2 coating for the oxidation protection of carbon fiber reinforced silicon carbide matrix composites

In order to improve the anti-oxidation performance of carbon fiber reinforced silicon carbide matrix (C/SiC) composites, ZrB₂ coating was prepared on the surface of C/SiC composites by a two-step technique of pack cementation method. The anti-oxidation properties of coated composites were investigated. The results showed that ZrB₂ coating was obtained by the method, which was homogenous and dense. The weight loss percentage of the coated composites was only 1.52 after oxidation in air at 1500 °C for 30 min, which exhibited excellent oxidation resistance.     

Boro-aluminising of P91 steel by pack cementation for protection against steam oxidation

Abstract

High performance alloys are often the materials used for various components exposed to high temperature environments. In many cases, protective coatings are applied in these alloys, providing higher corrosion and oxidation resistance, compared to the base material. This study investigates the feasibility to apply boro-aluminising treatment on P91 steel by pack cementation process, to increase the steel high temperature properties in oxidising and corrosive environments. Packs activated by AlCl₃, NH₄Cl and KBF₄ were used to carry out the coating deposition at a temperature of 715°C for 6 h. The coating formed was analysed by means of SEM and XRD, and the compounds formed were identified. Cyclic steam oxidation for a total of 1008 h at 650°C revealed an oxide scale of 50 μm for the uncoated P91 steel, while the coated steel shows practically no oxidation effect.     

Formation of MoSi2 and Al doped MoSi2 coatings on molybdenum base TZM (Mo–0.5Ti–0.1Zr–0.02C) alloy

Formation of aluminium (Al) doped molybdenum di-silicide (MoSi₂) coatings was studied to improve the high temperature oxidation behavior of TZM (Mo–0.5Ti–0.1Zr–0.02C) alloy. The pack composition of the halide activated pack cementation process was successfully optimized to form silicide and Al doped silicide coatings on the TZM alloy substrates. Mo(Si, Al)₂ phase was found to form at the outer layer of the coating prepared by doping Al in MoSi₂. A change in composition of the phases with increase in coating temperature was detected with Al doping, whereas un-doped silicide coating process was dominated by the formation and growth of MoSi₂ phase. Oxidation test and the characterization studies using SEM, EDS, XRD, and micro-hardness measurements indicated the improved performance of Al doped silicide coating during high temperature oxidation in dry air due to the formation of the protective alumina scale.     

Evaluation of Yttria Coated High Density Graphite with Silicon Carbide Interlayer for Uranium Melting Applications

Yttrium Oxide (Y₂O₃) deposited over High Density Graphite (HDG) by Atmospheric Plasma Spray (APS) process is highly desirable as a chemical barrier coating for reusable Uranium (U) melting crucibles in the pyrochemical reprocessing of spent metallic fuels. In the present study, an oxidation protective Silicon Carbide (SiC) interlayer coating over HDG has been achieved by pack cementation process. The high-temperature oxidation resistance and resistance to thermal fatigue failure of Y₂O₃ coating with and without SiC interlayer were evaluated by performing repeated thermal cycling studies at 1450, 1500 and 1550?°C. The durability performance of Y₂O₃ coating with SiC interlayer in the actual working environment was simulated by performing U melting studies using miniature size HDG coated crucibles. The microstructural, chemical and phase characterization of coatings prior and post thermal cycle failure were carried out by SEM/EDS and XRD techniques. It is observed that the SiC interlayer developed by novel pack cementation technique for the Y₂O₃ top coat extended the thermal cycling and life of the coating with U melting in inert argon gas environment significantly. The occurrence of micro-cracking over Y₂O₃ top coat with SiC interlayer perceived after 33, 30 and 25 thermal cycles at 1450, 1500 and 1550?°C, respectively.     

型钢垛型设计及CAD研究

描述了型钢垛型设计的主要内容，建立了型钢垛型设计的优化数学模型和方法，导出了常用型钢垛型设计计算公式，开发了型钢垛型ＣＡＤ系统，该系统设计型钢垛型灵活、方便、快捷。     

Y对Nb基体表面包埋渗铝涂层微观组织和生长机制的影响

通过向包埋渗铝剂中添加Y₂O₃粉末在纯Nb基体表面制备了Y改性的渗铝涂层,研究了Y对涂层微观组织和生长机制的影响。结果表明,Y对涂层的相组成和NbAl₃相的晶粒形态均无明显影响。随包埋剂中Y₂O₃添加量的增加,涂层表面的Y含量升高。Y改性后,涂层的生长机制由受Al原子的沿晶扩散控制转变为受Al原子的晶内扩散控制,降低了涂层的生长速率,并使NbAl₃相的柱状晶区形成了<010>//ND和<110>//ND的2种丝织构。