高频感应钎焊金刚石磨头的优化

在氩气保护下,将高频感应加热旋转的预黏结金刚石-钎料,制作成钎焊金刚石磨头。结果显示,钎焊金刚石磨头的金刚石-钎料间和钎料-基体间具有良好的冶金结合。用高频感应钎焊金刚石磨头钻削家用瓷砖时,在匀速旋转条件下制成的金刚石磨头性能优于静止不动条件下制成的金刚石磨头。     

金刚石磨片性能探讨研究

本文通过大量现场试验，对金刚石品级，浓度，粒度进行了分析筛选，并选出ＧＷ２，ＧＷ３号配方，按其配方烧结出金刚石磨片在几个厂家反复试用，结果证明：ＧＷ型金刚石麻片具有研磨效率高，使用寿命长，质量稳定，磨片适用性强，研磨表面光滑，整洁，完全可以代替金刚石来研磨建筑装饰材料。     

金刚石磨头电火花车削修整技术研究

工具的精确设计和修整是电解加工的研究难点之一。由于特殊的制造工艺,铜基烧结金刚石磨头存在较大的圆跳动误差。为减小圆跳动误差,需对金刚石磨头进行修整。为此,提出了一种新的修整方法——电火花车削修整技术。利用该技术,可将金刚石磨头的圆跳动误差修整到0.003 mm。利用已修整的金刚石磨头和未修整的金刚石磨头分别对304不锈钢进行电解磨削,通过宏观和微观对比发现,采用电火花车削修整的磨头磨削精度高,加工误差小,且加工表面均匀,表面粗糙度值低、质量好。     

DC-PCVD处理的金刚石磨头钎焊机理的研究

为解决金刚石工具上Cu基钎料和金刚石之间结合力弱的问题,将直流等离子体化学气相沉积(DC-PCVD)处理后的金刚石作为磨料,感应钎焊制作成金刚石工具。利用扫描电镜、能谱仪和X射线衍射仪等仪器对DC-PCVD处理前后金刚石整体形貌及其钎焊面的成分、微观形貌等进行分析研究。分析DC-PCVD处理后的金刚石表明,在其表面沉积了一层非晶碳膜;感应钎焊DC-PCVD处理后的金刚石显示,出露于钎料层外的金刚石棱边能保持良好的锋利度,金刚石钎焊面上形成均匀细小的钛碳化合物,并且碳化物之间的孔隙大小和分布都较为均匀,液态化合物充填这些化合物孔隙之间,能够增强钎料对金刚石的把持强度。用DC-PCVD处理后的金刚石磨料和原始金刚石磨料感应钎焊制成的金刚石磨头进行钻孔试验显示,DC-PCVD处理后的金刚石整体破碎率和脱落率都较低。     

等离子喷涂WC—Co—Ni涂层的高频感应加热后处理

为了用高频鹫加热叔感应加热后处理改善大气等离子喷涂ＷＣ－Ｃｏ－Ｎｉ涂层的性能,使用的喷涂粉末是用Ｎｉ－Ｐ合金加入到ＷＣ－Ｃｏ粉末中的方法产生出来的ＷＣ－Ｃｏ－Ｎｉ复合粉末。对涂层施以感应加热,可以Ｎｉ－Ｐ合金与ＷＣ－Ｗｏ－Ｎｉ涂层产生熔合,并使其与钢基体产生高强度的冶金结合,该试验中的一个创新技术是,在处理中应用于涂上表面的抗氧化软膏的使用,这就排除了必须在氢气气氛中进行了限制。对处理后的涂层性能     

管道焊接热处理设备的研制

阐述了管道热处理的重要性以及火焰加热、中频感应加热方法,指出火焰加热、中频感应加热方法存在的缺陷.介绍了一种高频感应加热电源及其工作原理、电气结构等关键技术问题,以及管道加热的实用方法.     

包覆钎料铝-钢螺柱焊接头组织及性能

采用包覆钎料感应加热方法,以AlSi钎料作为焊缝填充金属,对Q235钢螺柱和6061铝合金进行钎焊.利用光学显微镜、扫描电镜、能谱分析等表征方法,对接头的组织、成分和相组成等进行了分析.结果表明,AlSi钎料与铝母材反应充分,Si元素扩散至铝母材形成针叶状的共晶组织,焊缝近钢侧生成一条狭窄连续的Fe-Al金属间化合物,并沿垂直于铝基体的方向生成出胞状晶,金属间化合物层由Fe2Al5和FeAl3的混合相组织组成.力学性能测试表明,接头的抗剪强度最大为65 MPa,近钢侧金属间化合物的显微硬度值较高,接头断裂在金属间化合物区域,属于延性断裂.     

等离子喷涂WC-Co-Ni涂层的高频感应加热后处理

本研究的目的是用高频感应加热后处理来改善大气等离子喷涂WC_Co_Ni涂层的性能。使用的喷涂粉末是将Ni_P合金加入到WC_Co粉末中而生产出来的WC_Co_Ni复合粉末。对涂层施以感应加热 ,使Ni_P合金与WC_Co_Ni涂层产生熔合 ,并使其与钢基体产生高强度的冶金结合。最近一些试验中的一项创新技术是在处理中对涂层外表面采用抗氧化膏剂 ,这就排除了必须在氢气气氛中进行处理的限制。对处理后的涂层测试了有关显微结构、硬度、附着强度、抗摩擦磨损性能和孔隙率等性能     

增分熔融凝固加工工艺参数的探讨

对增分熔融凝固加工技术中的最主要的参数－电源电力进行了探讨,考察原电力与开始熔化时间、熔融区深度、熔融区温度、所得材料的微观组织之间的关系,并运用所得参数制得了高性能的材料。     

WC晶粒度对硬质合金/不锈钢钎焊接头微观组织与性能的影响

为了探讨不同晶粒度硬质合金的钎焊性能,采用3组晶粒度分别为0.7、1.0和1.6μm的WC-13%Co(含量为质量分数)硬质合金与不锈钢进行高频感应钎焊,并对钎焊后硬质合金的硬度和断裂韧性进行检测,对焊接接头的抗弯强度进行测量,分析焊接界面和断口形貌。结果表明晶粒度对硬质合金基体性能影响较大。钎焊后元素向硬质合金侧的扩散程度随晶粒度的增大而减弱,钎焊后靠近焊缝处硬质合金的硬度和断裂韧性变化率随着WC晶粒度的增大而增大。钎焊接头抗弯强度随着WC晶粒度的增粗先略增大后降低,当硬质合金晶粒度为1.0μm时的钎焊接头获得最大抗弯强度值为410MPa。随着WC晶粒度的增大,钎焊后接头断口处硬质合金的断裂形式从以沿晶断裂为主向以穿晶断裂为主变化。     

磨粒预钎焊烧结金刚石雕刻磨头的性能研究

针对烧结金刚石雕刻磨头在加工过程中胎体容易产生裂纹甚至断裂等问题,采用预钎焊金刚石磨粒制作了金刚石雕刻磨头。利用有限元仿真方法分析不同金刚石磨粒界面结构对节块的力学性能的影响;通过三点抗弯实验测试节块的强度;并通过加工性能实验测试3种雕刻磨头的性能。结果表明:仿真实验中胎体上的应力能较多地转移到预钎焊磨粒上,从而降低了胎体自身的应力,提高了胎体的力学性能;预钎焊磨粒节块的抗弯强度也高于常规金刚石节块,在金刚石体积浓度为100%时,强度提高32.3%;预钎焊金刚石雕刻磨头的加工性能优于常规金刚石雕刻磨头。     

自蔓延烧结在金刚石制品中的应用

本文主要介绍了自蔓延高温合成技术的发展和特点,阐述了自蔓延高温合成技术在金刚石制品工业中应用的必要性和意义,分析了自蔓延高温合成技术在金刚石制品工业中应用的可行性,并介绍了国内外的应用研究现状,提出了自蔓延高温合成技术在超硬材料制品中的应用需要进一步研究解决的问题。     

Influence of nanocrystalline Ni–Ti reaction agent on self-propagating high-temperature synthesized porous NiTi

Nanocrystalline Ni–Ti was used in self-propagating high-temperature synthesis (SHS) to fabricate porous NiTi. The SHS of porous NiTi using elemental powders was also prepared for comparison. Results showed that the main phase was NiTi with unreacted Ni when using elemental powders, which is detrimental to medical use. A large amount of Ti₂Ni secondary phase was also detected. By employing mechanically alloyed nanocrystalline Ni–Ti as a reaction agent, the secondary intermetallic phase (i.e. Ti₂Ni) was significantly reduced and the unreacted Ni was eliminated. The addition of 25 wt% nanocrystalline Ni–Ti reaction agent produced porous NiTi with an average porosity of 52–55 vol% and a general pore size of 100–600 μm under preheating temperatures of 200 and 300 °C. This general pore size in the range of 100–600 μm is beneficial to biomedical application for osseointegration. By further increase of the reaction agent to 50 wt% in the reactant, a porous NiTi part was produced at ambient temperature (i.e. no preheating was necessary) and a dense part was formed at preheated temperature of 200 °C due to the large amount of energies in the nanocrystalline reaction agent. This revealed that the use of nanocrystalline reaction agent effectively lowered the activation barriers for combustion synthesis reaction.     

钎焊金刚石工具磨削CFRP的试验研究

为改善碳纤维增强树脂基复合材料(CFRP)的磨边质量及提高刀具的使用寿命,本研究基于以磨代切的思想,制备了钎焊金刚石磨头并对CFRP进行了磨边试验。为了评价CFRP磨边的加工质量,定义了CFRP磨边质量的评价参数——毛边因子,分析了主轴转速以及金刚石粒度对CFRP磨边质量的影响。试验结果表明:在相同的磨削深度、工件进给速度下,主轴转速的增加有助于提高CFRP磨边质量;金刚石粒径越小加工质量越好,细颗粒磨头的加工表面粗糙度更低。     

Synthesis and characterization of multipod zinc oxide whiskers synthesized via a modified self-propagating high-temperature synthesis method

A self-propagating high-temperature synthesis (SHS) method, which features a 2-step heating process carried out in a closed chamber, was developed to prepare multipod ZnO whiskers (mZnOw). A compacted Zn powder was first heated at 370 °C in air to form a refractory layer of ZnO on the surface of Zn particles. Next, the SHS reaction was ignited by rapidly heating to ∼750 °C under different oxygen gauge pressures (PO₂) to obtain a loose white product mainly composed of mZnOw. It was found that the PO₂ strongly affected the reaction conversion and morphological features, along with the Zn-to-O ratio, of the as-synthesized products, which, in turn, might influence their photoluminescence and microwave absorption properties. A possible explanation for the effects of PO₂ on these characteristics was also proposed.     

用金刚石磨头数控加工轴对称非球面光学玻璃透镜

为了提高轴对称非球面透镜的形状精度,降低其精加工成本,用金刚石小磨头在不同的加工参数和数控走刀轨迹条件下对K9光学玻璃透镜进行铣磨实验加工。透镜的轮廓精度用三坐标测量机测量,通过测量的数据点计算非球面透镜的法向轮廓度误差,并用数控加工时磨头的有效切削半径进行补偿。实验结果表明:当数控走刀轨迹为平行精加工和等高精加工时,加工后非球面透镜的面型精度最大轮廓度偏差PV和误差平均值RMS分别为54.48 μm和22.88 μm、98.46 μm和28.88 μm;通过优化金刚石磨头的有效切削半径可以提高非球面透镜加工的面型精度,平行精加工后优化的非球面透镜面型精度PV和RMS值分别为44.52 μm和7.37 μm。      

自蔓延高温连接技术研究进展

自蔓延高温连接作为一种新型特种连接技术,近些年得到了长足的发展.该方法节约能源、生产效率高,可以广泛地用来焊接结构和性能相异的材料.论文综述了自蔓延高温连接技术的发展现状,详细介绍了其特点及其焊接工艺,重点分析了连接的中间层选择问题,总结了一些典型的异种金属材料及陶瓷与金属材料的连接研究结果.可以预见,随着研究的进一步深入,该方法必将得到更加广泛的应用.     

Effect of process parameter on the combustion temperature of laser-induced self-propagating high-temperature synthesized Al/TiC composites

Ignition phenomena in self-propagating high-temperature synthesis (SHS) of Al–C–Ti system were studied. The experiments were performed in quasi-adiabatic conditions. A CO₂ laser was used as external energy source and was set to the influence of Al content, laser power and particle sizes of powder on the ignition behavior. The results showed the combustion temperature depended strongly on Al content, laser power and particle sizes of Ti and C; but the particle size of Al had little effect on combustion temperature, at the same time, the effect of Al content on adiabatic combustion temperature, T_ad, was calculated. According to the calculation result, adiabatic temperature decreased with the increasing of Al content.     

Preparation a nickel-aluminide bonded diamond tool by self-propagating high-temperature synthesis and strengthening by nickel-chromium-phosphorus alloy and copper

Metal bonded diamond tools are normally manufactured by hot-press sintering, which is a high energy consuming process and using a large number of graphite moulds as well. Graphite dust is hazardous to operator's health and environment in machining of graphite mould. In present study, a metal bonded diamond tool is manufactured by self-propagating high-temperature synthesis (SHS) without hot press sintering and consuming of graphite moulds. In order to improve bonding of diamond grit and flexural strength of the tool for this method, nickel‑chromium‑phosphorus alloy and copper are introduced into nickel‑aluminum SHS in present study. The influence of nickel‑chromium‑phosphorus alloy and copper content on the combustion processes, the thermal behaviors, and the microstructures of the synthesized composite bonds are examined in detail. A diamond tool based on the optimized composite is prepared, and the grinding performance is examined. The results reveal that the addition of nickel‑chromium‑phosphorus alloy and copper inhibited the SHS reaction of nickel‑aluminum and reduced the combustion velocity, combustion temperature and reaction exothermic enthalpy. Copper can significantly improve flexural strength of the nickel aluminide bond. However, the maximum of nickel‑chromium‑phosphorus alloy or copper is about 60 wt% to sustain the SHS. A homogeneously dispersed and interconnected nickel-chromium-phosphorus phase in the matrix of nickel aluminides can be obtained with addition of over 40 wt% nickel‑chromium‑phosphorus alloy. A continuous chromium rich layer, composed of chromium carbide, has been formed at the interface between diamond grit and matrix, which renders a chemical bond of diamond grit. On the basis of the addition of 40 wt% nickel‑chromium‑phosphorus alloy and 10 wt% copper, an interconnected nickel‑chromium‑phosphorus phase for strong bonding of diamond grit and a flexural strength up to 700 MPa are achieved, which is considered as an excellent candidate material for diamond tools. The grinding test shows that the diamond tool owns a sound machining ability on the granite, and the diamond grit can be well retained and protruded.     

Phase-field modelling of self-propagating high-temperature synthesis of NiAl

A phase-field model is developed and used to simulate high-temperature synthesis of intermetallic compounds. The model is based on a thermodynamic formulation, which incorporates the formation of chemically ordered phases and the associated heat generation. In contrast to previous approaches to modelling of high-temperature synthesis of intermetallics, the present model can be used to analyse the kinetics of the process at the microstructure level. The model takes general thermodynamic and kinetic parameters as input and gives as output a spatially resolved sequence of phase formation, from which the overall reaction kinetics can be inferred. Thus, no additional assumption has to be made on the nature of the kinetic mechanisms or on the magnitude of the overall reaction rate. Beside prediction of the microstructure, the model captures the key thermal characteristics of the combustion synthesis in both modes of thermal explosion and self-propagation. The results of simulations, as applied to the case of intermetallic formation in a simplified Ni–Al system, are shown to be consistent with the existing experimental data.