Al2O3／TiC陶瓷—WC／Co硬质合金复合刀片的研制

采用热压烧结工艺制备了陶瓷－硬质合金复合刀片，其上层为具有一定厚度的Ａｌ２Ｏ３／ＴｉＣ陶瓷材料下，下层为ＷＣ／Ｃｏ硬质合金。分析表明：复合片中残余应力值的大小与其上下两层厚度之比ｈ／Ｈ值有关。Ｘ射线衍射、电子探针和扫描电子显微镜分析表明：烧结过程硬质合金和陶瓷材料中的元素在界面存在相互扩散，增加了界面结合强度，其界面类型为扩散型。     

Al2O3／TiB2陶瓷材料的高温摩擦磨损特性研究

研究了Ａｌ２Ｏ３／ＴｉＢ２陶瓷材料与硬质合金往复滑动摩擦时，在不同氢气和温度条件下的摩擦磨损特性，结果表明：随温度和气氛不同，材料的摩擦系数有着不同的变化规律。在高温空气气氛中摩擦时，ＴｉＢ２氧化生成的表面氧化膜可起到固体润滑剂的作用，并且能阻止Ｃｏ的扩用，减轻粘着，因而能降低摩擦系数并有利于提高材料的耐磨性能；而在高温氮气气氛中摩擦时，由于硬质合金中的Ｃｏｐ扩散到陶瓷材料中，使材料产生粘着磨损和     

烧结温度对Al2O3＋WC陶瓷强韧性的影响

采用不同常压烧结（ＣＰ）温度制备了Ａｌ２Ｏ３＋ＷＣ复合陶瓷材料。利用扫描电镜（ＳＥＭ）、Ｘ－射线衍射,能谱分析（ＥＤＡＸ）等手段和三点弯曲,单边切口梁等力学方法研究了该材料的组织结构、力学性能及增韧机制。结果表明,１６００℃烧结Ａｌ２Ｏ３＋ＷＣ陶瓷各相结合致密、分布均匀且晶普微细,其断裂形式为沿晶断裂,室温断裂强度为５２０ＭＰａ;断裂韧性为６．２ＭＰａ·ｍ＾１／２,第二相ＷＣ弥散分布细化了基本晶粒     

添加Cr2O3对Al2O3-TiC陶瓷烧结及纳米结构形成的影响

研究了Ａｌ２Ｏ３－ＴｉＣ陶瓷材料中Ｃｉ２Ｏ３添加剂对该陶瓷材料烧结致密度和力学性能的影响。Ｃｒ２Ｏ３与ＴｉＣ在高度有化学反应发生,反应产物在高温产生的液相有助于陶瓷材料的烧结。Ｃｒ２Ｏ３与Ａｌ２Ｏ３形成的连续固溶体,使Ａ２ｌＯ３晶格的活化从而也促进了Ａｌ２Ｏ３－ＴｉＣ陶瓷材料的烧结。ＴＥＭ研究表明：Ｃｒ离子高温时在ＴｉＣ中具有较高的溶解度,降温后淀析出许多纳米级含Ｃｒ的颗粒,使Ａｌ２Ｏ３－ＴｉＣ陶     

巴基管/纳米SiC陶瓷材料的研究

本文研究了巴基管／纳米ＳｉＣ陶瓷材料。初步讨论了在热压条件下,巴基管、烧结温度和添加剂对其机械性能的影响。结果表明,添加了巴基管后,纳米ＳｉＣ的抗弯强度（室温）和断裂韧性有所提高。优化的工艺方案是在ＳｉＣ中添加１０ｗｔ％的巴基管、１ｗｔ％的Ｂ４Ｃ,烧结温度２０００℃（保温１ｈ,压力２５ＭＰａ）;其性能达到：相对密度９４．７％、抗弯强度（室温）３２１．２２ＭＰａ、断裂韧性３．８２ＭＰａ·ｍ＾１／２。     

硬质合金基底镀钛对PcBN复合片界面过渡层及性能的影响

采用阴极磁控溅射镀膜工艺在YG8硬质合金基底表面镀上了一层致密的钛膜,和cBN、Ti、Al微粉在超高温高压条件下烧结合成一体的PcBN复合片。通过X射线衍射仪(XRD)、场发射扫描电子显微镜(SEM)、X射线色散能谱(EDS)研究了研究界面处的镀Ti层的扩散规律、作用机理,以及过渡层中Ti分布形式和存在物相形式对PcBN复合片性能的影响。结果表明:镀层Ti在界面与上下层发生化学反应和冶金结合,主要生成物相为TiC颗粒及TiAl、TiCo、CoAl合金,使界面结合更为紧密,同时还增强了复合片的整体力学性能。     

炭膜气体分离性能研究

以酚醛树脂为原料制备了炭支撑膜和炭－炭复合膜，研究了其气体分离性能。结果表明：炭支撑膜分离气体和机理包括努森扩散和粘性流；采用浸涂－干燥－炭化的工艺制备的炭－炭复合膜对Ｈ２／ＣＯ２具有较好的分离性能，Ｈ２／ＣＯ２分离系数达５．６，大于理想努森扩散的分离系数３．７。但在高压差时复合膜上ＣＯ２的表面扩散增强，使Ｈ２／ＣＯ２分离系数下降。     

SiO_2－C系复合陶瓷材料的导电特性

以ＳｉＯ２作为绝缘的高膨胀性基体材料，以石墨作为导电性粒子，将石墨粒子均匀地分散在ＳｉＯ２基体材料中，经１２５０～１３５０℃烧结２～４ｈ制得ＳｉＯ２－Ｃ系复合陶瓷材料。对该复合陶瓷材料导电特性的研究表明，当石墨的含量在５Ｗｔ％～８Ｗｔ％之间时，其电阻率会发生急剧的变化，变化的程度可达４～６个数量级。同时对复合陶瓷材料的导电特性用渗漏模型作了解释。     

导电Al2O3基陶瓷刀具材料的超声—放电复合加工技术研究

采用超声－放电复合加工技术对Ａｌ２Ｏ３／（Ｗ,Ｔｉ）Ｃ,Ａｌ２Ｏ３／ＴｉＢ２,Ａｌ２Ｏ３／ＴｉＢ２／ＳｉＣｗ三种Ａｌ２Ｏ３基陶瓷刀具材料表面定位方孔进行加工,研究了共加工机理和加工参数对不同陶瓷材料加工效率,加工表面粗糙度的影响,由于该复合加工技术有产地结合了超扬波加工和放电加工的特点,因而能高效,高质量地加工陶瓷材料。试验结果表明,在同样的加工条件下,材料去除率的大小顺序为Ａｌ２Ｏ３／（Ｗ,Ｔｉ     

W18Cr4V钢表面激光熔覆Al2O3陶瓷涂层的组织结构

研究了Ｗ１８Ｃｒ４Ｖ钢表面Ａｌ２Ｏ３／ＮｉＣｒＡｌ复合陶瓷涂层的组织结构、成分分布及界面组织特征。结果表明：Ａｌ２Ｏ３／ＮｉＣｒＡｌ复合陶瓷等离子喷涂层的组织呈层片状,面层由α－Ａｌ２Ｏ３和少量的γ－Ａｌ２Ｏ３组成,层间为机械结合界面,界面处成分变化梯度较大。经激光重熔后的面层组织为单一的α－Ａｌ２Ｏ３柱状晶,Ａｌ２Ｏ３与中间合金ＮｉＣｒＡｌ间存在明显的界面反应,且界面相增多,在ＮｉＣｒＡｌ与基体     

The effect of tungsten buffer layer on the stability of diamond with tungsten carbide–cobalt nanocomposite powder during spark plasma sintering

WC–Co nanocomposite powder produced by spray pyrolysis–continuous reduction and carbonization technology, diamond coated with tungsten (W) by vacuum vapor deposition and uncoated diamond were used in this study. This work adopted the spark plasma sintering (SPS) process to prepare diamond-enhanced ultrafine WC–Co cemented carbide composite material. The effects of W buffer on the stability of diamond with WC–Co nanocomposite powder during SPS were investigated. Results showed that the uncoated diamond was mechanically embedded in WC–Co cemented carbide matrix, while the diamond coated with tungsten was combined chemically with WC–Co cemented carbide matrix. Moreover, there was a transitional layer between the diamond and the matrix which could improve the thermal stability of the diamond, prevent carbon atom of the diamond from dissolving in Co phase and increase the bonding strength of the interface between the diamond and the matrix.     

Quantitative determination of the adhesive fracture toughness of CVD diamond to WC–Co cemented carbide

Well-separated diamond particles were nucleated and grown by hot filament chemical vapor deposition (HFCVD) onto WC–Co cemented carbide pretreated by Murakami’s reagent and H₂O₂+H₂SO₄ solution. The adhesive strength of diamond particles to WC–Co cemented carbide was quantitatively determined in terms of interface toughness by directly applying an external load to the CVD diamond particles. From the measurement of the maximum load required to scratch off the particles, we determined that the adhesive toughness was 14 J/m². This value is more than twice as high as that of CVD diamond on smooth silicon substrate and comparable to the cleavage fracture energy of diamond. The newly developed procedure will allow to check the effectiveness of substrate surface pretreatments for further improving the adhesion level of diamond films on WC–Co.     

粉末涂层陶瓷材料的涂层工艺及涂层机理

对使用Ａ２Ｏ３溶胶在硬质合金粉末表面涂层Ａ１２Ｏ３陶瓷进行了研究。重点探讨了基体粉末的表层处理、粉末涂层对Ａ１２Ｏ３涂胶的要求以及使用Ａ１２Ｏ３溶胶涂层硬质合金粉末的涂层工艺,最后,对有些硬质合金粉末引起Ａ１２Ｏ３溶胶在涂层过程中发生凝胶的凝胶机理、粉末涂层法的涂层机理进行了分析。认为硬质合金粉末对Ａ１２Ｏ３溶胶中胶体粒子的离子氛围的影响是使溶胶发生凝胶与否的关键。涂层机理则是硬质合金粉末表面通过     

Microstructure,mechanical properties,and cutting performances of WC-Co cemented carbides with Ru additions

In this study, the microstructure, mechanical properties, and cutting performance of WC-8Co cemented carbide with different Ru additions were studied in detail. The results show that Ru can inhibit the abnormal growth of WC grains and the mean grain size of WC grains decreases. Ru can result in the lattice distortion of Co phases and promote the phase transition of Co from face-centered cubic (FCC) to hexagonal closepacked (HCP) as Ru can reduce the stacking fault energy of Co phases. The proportion of HCP Co phases increased from 14.4 to 39.6% with increasing Ru content. Meanwhile, among the five groups of cemented carbides with different Ru additions, cemented carbides with 1.5 wt% Ru exhibit the highest hardness of 1382 HV and transverse rupture strength (TRS) of 3790 MPa. The enhanced hardness and TRS were due to solid solution strengthening and phase transition of Co, respectively. The fracture toughness of cemented carbide was enhanced from 16 MPa m^−1/2 with 0 wt% Ru to 19 MPa m^−1/2 with 0.5 wt% Ru. Additionally, during the dry cutting of Ti–6Al–4V, the diffusion of Ti and Al elements is hindered. Therefore, the wear resistance of the tools is improved. The cutting lifetime of the cemented carbide tools with 0.5 wt% Ru increased three-fold compared to those without Ru addition.     

自蔓延离心熔铸TiB2-(Ti,W)C-TiC陶瓷研究

基于离心热爆反应、难熔液相分离与快速凝固原理,选取(WO3+Al+C)体系辅助(B4C+Ti)反应体系,采用自蔓延离心熔铸工艺可以成功制备出TiB2微纳米晶补强TiC-(Ti,W)C陶瓷基复合材料.将(B4C+Ti)、(WO3+Al+C)两种反应体系依次装填入坩埚中进行SHS离心熔铸实验,发现因W-Ti-C液相动力学粘度的降低、Al2O3液滴迁移路程减小,极大促进Al2O3液滴的Stokes上浮过程,故而显著减小残存于陶瓷基体上的氧化物夹杂含量与尺寸,进而TiB2微纳米片晶诱发的强烈自增韧机制与Al2O3微纳米晶产生的残余应力增韧效应,使得TiB2-(Ti,W)C-TiC陶瓷的弯曲强度、断裂韧性与维氏硬度分别达到(952±25)MPa、(12.6±2.5)MPa·m1/2与(28.6±1.2)GPa.     

A study of CVD diamond deposition on cemented carbide ball-end milling tools with high cobalt content using amorphous ceramic interlayers

In this paper, CVD diamond coatings are deposited on cemented carbides with 10 wt.% Co using amorphous SiO₂ and amorphous SiC interlayers. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Raman spectrum and X-ray diffraction (XRD) are carried out to characterize the microstructure and composition of as-deposited films. Moreover, the adhesion and cutting performance of as-fabricated diamond coatings are studied. Indentation tests show that the amorphous ceramic interlayers can enhance the adhesion between diamond films and WC–Co substrates. The cutting tests against zirconia indicate that the tools with amorphous ceramic interlayered diamond coatings exhibit improved cutting performance. The amorphous ceramic interlayers can improve the adhesive strength and wear endurance of diamond coatings on WC–10 wt.% Co substrates, which provide a viable way for adherent diamond coatings on cemented carbide tools with high cobalt content.     

Room-Temperature Thermal Conductivity of Cemented Transition-Metal Carbides

Measurements are reported of the room-temperature thermal conductivity of cemented multicarbides (WC-TiC _x -NbC _x -TaC _x /Co) and straight tungsten carbide (WC/Co), which are widely used tool materials. The thermal conductivity of cemented titanium carbide was found to be lower than that of cemented tungsten carbide. The difference is attributed to strong phonon and electron scattering from carbon atom vacancies in the nonstoichiometric cubic carbide TiC _x ; these defects are absent in stoichiometric hexagonal WC. Higher binder contents in tungsten carbide samples lowered the overall thermal conductivity. Scattering of electrons and phonons by C and W atoms in solid solution in the binder phase presumably reduces its thermal conductivity. No dependence on grain size was detected.     

Effect of carbon nanotubes additives on mechanical properties of WC–6Co cemented carbide

In order to increase the toughness of WC–6Co cemented carbide, different contents of carbon nanotubes (CNTs) were added to the WC–6Co alloy powder to prepare cemented carbide by low-pressure sintering. The results showed that some of the CNTs were embedded between the grains of WC–6Co cemented carbide, which would hinder the growth of WC grain boundary, thus leading to grain refinement. In addition, CNTs inhibited the formation of decarbonized phase and guided the deflection and bridge of crack to hinder the crack extension. With the increase of CNTs content, the density increased at first and then decreased, and the transverse fracture strength increased at first and then decreased. When the content was 0.2 wt.%, the alloy had the best performance. The density of the alloy was 99.67%; the transverse fracture strength was up to 2937.5 MPa, which is about 100% higher than that of cemented carbide without CNTs. The fracture toughness was 9.84 MPa m^1/2, and the hardness was 1924.8HV₃₀.