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〗〓〓 〖     

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。     

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.     

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。     

Creep and corrosion testing of aluminide coatings on ferritic-martensitic substrates

Pack and chemical vapor deposited (CVD) aluminide coatings on commercial ferritic-martensitic Fe-9Cr-2W steel are being investigated by creep and corrosion testing at 650 °C. Results from different coating thicknesses show that the coated region makes no contribution to the creep strength. The creep behavior of uncoated material was studied after various heat treatments to simulate the coating process and typical secondary heat treatments. Alternating creep and corrosion exposures showed little effect on the creep strength of uncoated material but coated materials became progressively weaker. The coatings were protective in wet air at 650 °C after creep testing.     

Mechanical behavior of coated T91 steel in contact with lead-bismuth liquid alloy at 300 °C

Different coatings, deposited by pack cementation process, were developed to protect the T91 steel against dissolution by Lead Bismuth Eutectic (LBE): iron aluminide, iron boride and an iron solid solution enriched in chromium and covered by carbide. The mechanical behavior of the T91 steel with the different coatings is studied in air and in LBE at 300 °C by the use of the Small Punch Test (SPT). Though the coatings are brittle, they do not affect the mechanical strength of the substrate in air, except the iron boride one. In LBE, the most critical situation is found when fracture of the interface between the T91 steel and the coating occurs. Then, the coating provides the set of conditions to trigger liquid metal accelerated damage.     

柴油机活塞环组密封润滑分析

良好的密封和润滑是活塞环长期稳定运行的保障。在气密性仿真分析的基础上,建立了活塞环组的贫油润滑模型,提出了一种新的边界条件求解润滑模型。利用MATLAB仿真程序,完成了PA6-280柴油机活塞环组的密封与贫油润滑分析。结果发现,在密封性能良好的条件下,活塞环组处于一种非稳态的混合润滑状态,并且各个活塞环的润滑受先导环的润滑油供给情况影响很大。