高能机械研磨纳米结构WC-Co复合粉末的研究

采用高能机械研磨制备纳米结构ＷＣ－Ｃｏ复合粉末,研磨后的纳米结构ＷＣ－Ｃｏ复合粉末受用Ｘ射线衍射,高分辨透射电镜,Ｘ射线能谱仪分析其微观结构。研究发现经过高能机械研磨,ＷＣ的晶粒尺寸能降低到１０ｎｍ以下,纳米尺度的ＷＣ晶粒被Ｃｏ薄层覆盖物分离,ＷＣ晶粒的形貌为似球形,并且ＷＣ晶粒中产生了大量的晶格缺陷。     

纳米级W-Ni-Fe-Y系硬质合金复合氧化物粉末的制备

用Ｈ２ＷＯ４和ＮｉＣｌ２碱性水溶液与ＦｅＣｌ２和Ｙ２Ｏ３的酸性水溶液快速混合方法，在超声喷雾热转换装置中制备ＷＮｉＦｅＹ系纳米级复合氧化物粉末。通过Ｘ射线衍射及透射电镜分析，研究了复合粉末的物相组成、颗粒形貌及粒径范围．结果表明，采用上述两种溶液快速混合及超声喷雾热转换的方法，可以制备成分均匀的复合氧化物粉末。其物相组成为ＷＯ３，ＮｉＯ，Ｙ２Ｏ３，粉末的千粒平均粒径为３２ｎｍ，颗粒形貌近似球形，用ＢＥＴ法测定的粒径为３０ｎｍ。     

喷涂硬质合金界面的研究

利用电子显微镜观察和研究了超音速喷涂ＷＣＣｏ／弹簧钢界面的微结构特征。发现超音速喷涂使ＷＣＣｏ涂层具有纳米微晶γ粘结相包埋ＷＣ粒子的微观结构，在基体一侧有约２μｍ厚的钨原子扩散层，说明超音速喷涂的涂层与基体间不只是一种机械结合，还有相互间的原子运动。这些微观特征是超音速喷涂ＷＣＣｏ涂层具有高性能的主要原因     

流化床还原碳化法制备超细WC—Co复合粉末

介绍了一种制备超细ＷＣ－Ｃｏ复合粉末的新工艺－流化床还原碳化法。ＸＲＤ分析结果表明，该法制备的粉末由ＷＣ和Ｃｏ两相组成。Ｘ－射线小角衍射测定粉末的平均颗粒度为０．１２μｍ。将该粉末压制成的样品在１２８０℃真空烧结１ｈ获得９９．７％理论密度的试块。     

流化床还原碳化法制备超细WC－Co复合粉末

介绍了一种制备超细ＷＣ－Ｃｏ复合粉末的新工艺─—流化床还原碳化法。ＸＲＤ分析结果表明，该法制备的粉末由ＷＣ和Ｃｏ两相组成。Ｘ－射线小角衍射测定粉末的平均颗粒度为０．１２μｍ。将该粉末压制成形的样品在１２８０℃真空烧结１ｈ获得９９．７％理论密度的试块。     

预弥散强化镍粉——硬质合金的新型粘结剂

叙述了以预弥散有纳米Ａｌ２Ｏ３的镍粉代替钴粉作粘结剂以提高ＷＣＮｉ硬质合金性能方面的初步研究；制得的ＷＣＮｉ硬质合金的物理机械性能可达到ＷＣＣｏ合金的水平     

专利文摘

专利申请号 :９８１１０７０８公开号 :１２０３８４０发明名称 :复合碳化还原制备纳米碳化钨—钴复合粉体的方法文摘 :本发明公开了一种引入内部碳化源的复合碳化还原制备纳米碳化钨—钴复合粉体的方法。该方法在制备钴盐或钨盐溶液时 ,加入有机物 ,这些有机物含有能提供弧电子对的配位基团 ,能与２价钴Ｃｏ２ +或６价钨Ｗ（Ⅵ）的水溶液发生络合反应 ,形成配位化合物 ,然后采用共沉淀技术制备含Ｗ、Ｃｏ金属盐及有机基团溶胶分散体 ,并通过喷雾干燥和还原碳化过程获得纳米碳化钨—钴复合粉体 ;本发明同时设计了一套回收还原碳化尾气的系统…     

硬质合金用Ni／Co复合粉末的研究

研究了采用草酸盐共沉淀法制取硬质合金用Ｎｉ／Ｃｏ复合粉末，粉末成分为Ｎｉ：Ｃｏ＝１：１。结果表明，共沉淀反应强烈依赖于溶液的ｐＨ值，而粉末粒度和成分的均匀性取决于反应温度。用此复合粉末制作的硬质合金凿岩钎头的性能不亚于ＷＣ－Ｃｏ硬质合金。     

超细晶粒WC基硬质合金的工业化制备技术

武汉工业大学向社会推出超细晶粒ＷＣ基硬质合金的工业化制备技术 ,受到有关方面关注。据介绍 ,用流态化连续还原碳化技术制备了纳米晶ＷＣ Ｃｏ原料粉末 ,其质量达到超细晶粒硬质合金的实用要求 ,完全无缺碳相、游离碳≤ 0 10 % (质量分数 ) ,氧含量≤ 0 2 0 % (质量分数 ) ,晶粒度≤ 0 10 μｍ ,达到国际先进水平 ,选择的制备工艺适合于扩大规模生产 ;研究了分散剂和抑制剂的作用机理、成型剂的引入及脱除、真空烧结、低压烧结、热等静压处理等工艺对超细晶粒ＷＣ Ｃｏ硬质合金性能的影响。所制合金的晶粒度≤0 5 μｍ ,洛氏硬度为 90…     

添加标样法测定WC—Co硬质合金γ相的组成

添加标样法测定ＷＣＣｏ硬质合金γ相的组成刘寿荣刘宜（天津硬质合金研究所，天津３００２２２）（山东大学）关键词：ＷＣＣｏ硬质合金γ相Ｘ射线衍射１前言鉴于工业钴粉和ＷＣＣｏ硬质合金的γ相（钴基ＣｏＷＣ固溶体）都是ｆｃｃ（β）型和ｈｃｐ（α）型两...     

Synthesis of nanostructured WC-12 pct Co coating using mechanical milling and high velocity oxygen fuel thermal spraying

A nanostructured WC-12 pct Co coating was synthesized using mechanical milling and high velocity oxygen fuel (HVOF) thermal spraying. The variation of powder characteristics with milling time and the performance of the coatings were investigated using scanning electron microscope (SEM), X-ray, transmission electron microscope (TEM), thermogravimetric analyzer (TGA), and microhardness measurements. There is no evidence that indicates the presence of an amorphous phase in the sintered WC-12 pct Co powder, and the binder phase in this powder is still crystalline Co. Mechanical milling of up to 20 hours did not lead to the formation of an amorphous phase in the sintered WC-12 pct Co powder. During the initial stages of the milling, the brittle carbide particles were first fractured into fragments and then embedded into the binder phase. This process gradually formed polycrystal nanocomposite powders of the Co binder phase and W carbide particles. The conventional cold welding and fracturing processes primarily occurred among the Co binder powders and polycrystal composite powders. The nanostructured WC-12 pct Co coatings, synthesized in the present study, consist of an amorphous matrix and carbides with an average particle diameter of 35 nm. The coating possesses an average microhardness of 1135 HV and higher resistance to indentation fracture than that of its conventional counterpart.     

Al_2O_3/C复合材料中抗氧化添加剂对预氧丝原位碳化及强度的影响

研究了不同抗氧化添加剂B_4C粉、SiC粉和铝粉对碳纤维前驱体即预氧丝在氧化铝/炭复合材料中原位碳化的影响及其碳化后纤维对材料的强化效果。研究表明,在氧化铝/碳复合材料中添加B_4C后,由于高温下在材料表面形成了一薄层致密的玻璃相物质,抗氧化效果最为明显,预氧丝原位碳化后达到同类碳纤维的强度,复合材料强度也大幅度提高。其次,添加少量铝粉也能起到较好的保护作用。     

尿素对前驱物及氮化铝粉末粒度形貌的影响

以硝酸铝、葡萄糖为原料,用碳热还原法制备氮化铝粉末,研究尿素对前驱物及其氮化反应产物的组成和显微形貌的影响,发现尿素不仅可以影响前驱物的组成和显微形貌,还对氮化反应产物的显微形貌有重要影响。在溶液里添加尿素后,它与硝酸铝发生了低温燃烧合成反应,生成了比表面积高的泡沫状前驱物,该过程中碳由于燃烧损失较大,在没有添加尿素的溶液中,没有燃烧反应发生,碳的损失小,生成的前驱物团聚现象严重,比表面积低,两种前驱物保留了前驱物的形貌特征,对于不添加尿素合成的前驱物,在其氮化反应后所生成的氮化铝粉末板结严重;而添加尿素合成的前驱物的氮化反应产物是由球形颗粒组成的软团聚体。利用XRD,SEM等分析方法对粉末进行了表征。     

前驱体碳化粉末反应火焰喷涂制备TiC增强金属复合涂层

采用前驱体碳化复合技术制备了Ti-Fe-C和Ti-Ni-C两种体系的反应热喷涂复合粉末,通过氧乙炔火焰喷涂原位合成并沉积了TiC增强Fe基和Ni基复合涂层.利用XRD、SEM和EDS研究了复合粉末、涂层的相组成和组织结构,考察了TiC/Fe、TiC/Ni复合涂层的硬度和耐磨性.结果表明: 复合粉末在喷涂过程中反应充分,可分别生成以Fe和Ni为粘结相的TiC增强涂层;两种涂层都是由TiC颗粒均匀分布的复合强化片层和TiC聚集片层叠加而成,TiC/Fe复合涂层的片层较薄,而TiC/Ni涂层中TiC的聚集片层较少;TiC/Fe涂层的硬度高于TiC/Ni涂层,两者的耐磨性能分别约为Ni60涂层的11倍和6倍.     

Mechanico-Chemical Synthesis,Structure and Properties of Alloys Based on the System Ti ― Al

The kinetics of structure and phase formation in Ti Al and Ti Al Sc alloy powders in the process of mechano-chemical synthesis from elemental powders was investigated. It was established that the formation of microdimensional x-ray amorphous composite particles with nanodimensional structural components occurs. It was shown that in consolidation of the mechanically alloyed powders by hot isostatic pressing structural heredity is realized, and that the materials produced have unusually high microhardness compared to that of similar cast alloys. This is characteristic of nanostructured materials. In addition to high hardness the materials are characterized by high work of plastic deformation at room temperature. Microalloying the alloy powders with scandium has a complex positive effect on the strength properties of the hot pressed materials, due to the formation of a dispersion hardened microstructure with purified nanodimensional grains.     

Bulk Nanostructured Materials

This paper will address three topics of importance to bulk nanostructured materials. Bulk nanostructured materials are defined as bulk solids with nanoscale or partly nanoscale microstructures. This category of nanostructured materials has historical roots going back many decades but has relatively recent focus due to new discoveries of unique properties of some nanoscale materials. Bulk nanostructured materials are prepared by a variety of severe plastic deformation methods, and these will be reviewed. Powder processing to prepare bulk nanostructured materials requires that the powders be consolidated by typical combinations of pressure and temperature, the latter leading to coarsening of the microstructure. The thermal stability of nanostructured materials will also be discussed. An example of bringing nanostructured materials to applications as structural materials will be described in terms of the cryomilling of powders and their consolidation.     

Enhanced magnetic properties of anisotropic Nd-Fe-B nanocomposites by Fe(C)coating

Nanostructured anisotropic Nd-Fe-B/Fe(C) composite powders were prepared by coating Fe(C) softmagnetic nanoparticles on HDDR Nd-Fe-B hard magnetic powders using iron pentacarbonyl Fe(CO)_5 as soft-phase precursor.The effect of Fe(CO)_5-loading amount on soft-phase purity,coating morphology and magnetic properties of the composite powders was investigated.Dense and continuous Fe(C) softphase coatings with average particle sizes of 58-68 nm are obtained at Fe(CO)_5 loading amounts of x 12 wt%,leading to enhanced remanence and improved energy product of the coated powders.Positive value in δM-plots and single-phase-like demagnetization curves are observed in the Nd-Fe-B/Fe(C) composite powders,indicating the exchange coupling effect between the coated Fe(C) soft phases and the Nd-Fe-B hard phase.     

Production and properties of AlN–BN composite

Powder Metallurgy and Metal Ceramics - The nitridation of an AlB2 precursor in a controlled nitrogen flow is examined with the aim of obtaining AlN–BN composite powders. It is shown that...     

Fabrication of W–20%Cu composite powder from copper and tungsten salts

Abstract

An investigation has been made to prepare homogeneous powders of CuWO₄ and WO₃ from ammonium paratungstate and copper nitrate to prepare nanosized W–Cu powder. Hence, a mixture of ammonium paratungstate and copper nitrate with predetermined weight proportion was made in distilled water; while the content of the beaker was being stirred at a certain speed to reach the desired composition of W–20 wt-%Cu. Mixture was heated to 80–100°C for 6 h. Also, pH range was adjusted at about 3–4. The mixture was then evaporated and dried in the air. To reach W–Cu composite powder, the precursor powders burned out at 520°C for 2 h in the air to form W–Cu oxide powder and then were ball milled and reduced in H₂ atmosphere to convert it into W–Cu composite powder. The resulting powders were evaluated using scanning electron microscopy, X-ray diffraction, thermogravimetric analysis and differential thermal analysis techniques. The results showed that homogeneous powders of W–Cu with particle size of ～100 nm and a nearly spherical shape could be obtained by this process.