Current product technology from the tool, the tungsten carbide cutting tools gradually replace high-speed steel cutting tools, in particular circular tool. Coated tungsten carbide cutting tools are becoming more common, according to the main chemical components distinguish tungsten carbide cutting tools can be divided into groups based tungsten carbide and titanium tungsten carbide tungsten carbide cutting tools. Including tungsten carbide cobalt-based alloy (YG), tungsten, titanium, cobalt class (YT) and add carbonation rare class (YW) three main components of tungsten carbide (WC), titanium tungsten carbide (Tic), niobium tungsten carbide ( NbC), commonly used metal bonding phase is Co. Tic titanium tungsten carbide tungsten carbide based cemented tungsten carbide is the main component, commonly used metal bonding phase is Mo and Ni.

The correct selection of a suitable cutting tool material, can improve work efficiency, improve processing technology has important significance machinery manufacturing needs. We know that, in addition to cutting tool materials should have the hardness and wear resistance, strength and toughness and economy, the tungsten carbide cutting tools must also meet the following requirements: reliability, high heat resistance and thermal shock resistance, good high temperature mechanical properties and so on. The nature of production, machine type, CNC machining program, the size and shape of the workpiece and the machining accuracy are factors tungsten carbide cutting tools materials processing.


 

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EDM process parameters can be divided into electrical and non-electrical parameters parameters. The main parameters of the electrical parameters of pulse power is there between processing polarity, pulse width, pulse peak voltage, peak current, and so on. Non-electric parameters are mainly flushing or pumping the way, pressure, flow, carrying knives height, frequency, translational mode, the size of the flat momentum, they influence each other, allelopathy, to select the parameters more difficult.

In order to correctly select the gage EDM parameters to follow, people under the tool electrode material of the workpiece, if the tool polarity, pulse width, peak current, etc. The main parameters of the surface roughness, the discharge gap, ablation rate The four main process indicators affect electrode wear rate and, prior to make technology curve chart, click here to select EDM gage.

EDM machining mold or some parts, usually workpiece material has been previously set, carbon steel, tool steel, stainless steel, nickel-chromium alloy steel of various types of steel material and so can be counted on the EDM, they are is processing performance, process indicators are similar. Including melting point, high vaporization point of tungsten, molybdenum alloys and carbide materials and graphite, copper, tungsten, silver, tungsten sintered materials, conductive polycrystalline diamond, etc. can be counted as another kind of processing power are difficult for them processing materials. Aluminum, zinc, brass and other low melting point of the material, EDM easier. In short, the first step is we analyze the characteristics and technical requirements of the workpiece (eg rough surface, size, tolerance precision) and other technology indicators on the basis of the workpiece material and technical requirements to select the tool electrode materials such as brass, copper, stone or copper tungsten, silver tungsten alloys, of course, to consider whether they are easy to manufacture a tool electrode and the costs and other factors.




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After the tungsten carbide grain refinement, the hard phase size becomes smaller, the binder phase is more evenly distributed around the hard phase, can increase the hardness and wear resistance of cemented tungsten carbide. Such as the appropriate use of cobalt content, but also to improve the flexural strength and fracture toughness. Mining or drilling for coarse tungsten carbide grains, the average grain size of 4 ~ 5μm; fine grain tungsten carbide cutting tools grades generally used as TY15, YG6 so are grains, the average grain size of 2 ~ 3μm; average grain size of the fine grain tungsten carbide cutting tools for 1 ~ 2μm; submicron grain tungsten carbide for 0.5 ~ 1μm; ultrafine grain tungsten carbide at 0.5μm or less.

Ultra-fine grain tungsten carbide cutting tools grains due to its fine, the blade can be sharpened, smooth; at the same time because of its high strength and hardness, and it could have a long time to maintain a very small edge radius and roughness . Therefore, in the processing of heat-resistant alloy, use YS2, YM051, YM052, YD05 and other ultra-fine grain tungsten carbide cutting tools, than using YT, YG, YW3 class ordinary tungsten carbide cutting tools for better heat resistance and integrated wear resistance.


 

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After decades of continuous development, the hardness of tungsten carbide cutting tools has reached 89 ~ 93HRA, at a high temperature of 1000 ℃ still has good red hardness, which is several times the durability of high-speed steel cutting tools. tungsten carbide is WC, TiC, TaC, NbC, VC and other refractory metal tungsten carbides and prepared by powder metallurgy from iron group metals as a binder. Compared with the high-speed steel, it has high hardness, wear resistance and red hardness; compared with superhard material, it has a higher toughness. Because of tungsten carbide cutting tools has a good overall performance, so in the tool industry has been widely used.

Diverse types of tungsten carbide cutting tools. In the past, the International Organization for Standardization (ISO) has the tools, tungsten carbide cutting tools are divided into three categories: P class, mainly used for cutting steel; K class, mainly used for cutting cast iron; M class, for the ordinary type tungsten carbide. In recent years, the increasing number of types of processed materials, ISO and the addition to the three types of tungsten carbide, namely H class, mainly for high cutting hard materials such as hardened steel, chilled cast iron; S class for cutting heat materials, high-temperature alloys; N class for cutting non-ferrous metals.



 

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The films annealed at 200C and 300 C display violet–red under the sunlight as well as the as-deposited ones. Nevertheless, the film annealed at 400C exhibits transparency and appeared to be blue colored. The film annealed at 200C is amorphous, i.e. does not exhibit diffraction peaks while those annealed at 400C exhibit several sharp diffraction peaks, indicating the crystallization of this film happened. The peaks shown in Figs. 1(b) and 1(c) can be attributed to a mixture of polycrystalline phases, which includes hexagonal h-WO3 phase (JCPDS PDF-33-1387) and triclinic t-WO3 phase (JCPDS PDF-30-1387). It is also seen that the films annealed at 400C were dominated by hexagonal h-WO3 phases. Acosta et al. had prepared the tungsten oxide thin films by sputtering WO3 bulk. Their results indicated that the films mainly contained hexagonal h-WO3 phase and monoclinic α-WO3 phase. Usually, the polycrystalline monoclinic and triclinic phases can be observed in the films deposited by reactive magnetron sputtering from W target, but few reports have also shown the presence of hexagonal phases. we can see that the growths of the film along (002) and (200) orientations of the triclinic phases are enhanced when thermal treatment time at 400C is prolonged from 60 min to 180 min.

Under our experimental conditions, the thickness d of the as-deposited film has been determined to be about 220 nm by an observation of its section SEM. SEM images of the thin films annealed at different temperatures. All the sample films are very compact. The sizes of the sputtered tungsten oxide grains look very uniform and are a little less than 100 nm. The grain boundaries become more and more discernable as the annealing temperature increases from room temperature to 400C, whereas they become very indistinct again owing to the growth of the grains when the annealing time is prolonged from 60 min to 180 min at 400C. This process indicates the structure transformation of the sample films from the complete amorphous nature to crystallization and is in complete agreement with the results confirmed by XRD. The surfaces of the deposited films become rougher as the annealing temperatures rise. When the annealing time at 400C increases from 60 min to 180 min, the nanorod-like structures have grown from the surface of the deposited film. This kind of surface morphology of the samples is very different from those of the films prepared by sol–gel methods and by reactively sputtering tungsten metal target.

It is well known that during the sputtering, the interaction between Ar plasma and WO3 bulk can highly distort and tilt the form works of the WO6 octahedra and thus results in an amorphous film. At the same time, a large number of oxygen vacancies and defects, which can reduce the tungsten ions from W6+ to W5+ or W4+,would be produced in the deposited films. This is responsible for the violet–red color and the amorphous XRD data of the films annealed below 300C. The obvious crystallinity of the deposited films at 400C for 60 min implies that the defects and disordered structures in the films have been effectively activated by this temperature. Consequently, increasing the annealing time at 400C is obviously favorable to the crystallinity and the growth of the films.

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Vacuum electronic devices have a wide application in civil and military fields such as communication, radar and industrial heating. Cathode is an important component in the device since it provides the required electronic beam for the device. Among all the electron emitters, scandate cathodes have aroused great attention among all the cathodes due to their copious emission property.

It has been found in the previous work, the raw powder properties such as morphology, particle size and size distribution greatly affected the emission property of the cathode. The diffusion and distribution uniformity of rare-earth elements would be enhanced if the structure dimension of the emitter decreased from micrometer to sub-micrometer even to nanometer, i.e., the electron emission property of emitter would be improved with the diminution of the micro-structure dimension of cathode matrix.

Scandium oxide doped tungsten powders have been prepared by a new method of spray drying combined with two-step hydrogen reduction. Spray drying has some advantages such as the particle size can be controlled in the single step.

The addition of Sc2O3 shifted the hydrogen consumption peak to the lower temperature side. Namely, the reduction temperature of tungsten oxide decreased with Sc2O3 addition. Adding scandia could decrease the particle size of tungsten. The scandia doped tungsten powder prepared by spray drying method had sub-micrometer size in the range of 0.1μm to1μm in semispherical shape and scandium distributed evenly in the powder. Using scandia doped tungsten powder, sub-micro-structure cathode matrices with semispherical grains and homogenous distribution of scandium was obtained.

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Scandia doped tungsten powders were prepared by spray drying combined with two-step hydrogen reduction. The particle size of doped tungsten powder, powder morphology and doped tungsten matrix were characterized by scanning electron microscope, X-ray diffraction and laser diffraction particle size analyzer, respectively. The reduction behavior of Sc2O3 doped tungsten oxide and the effect of Sc2O3 onthe property of tungsten powder were studied by the temperature programmed reduction. The experimental results showed that the precursor powders prepared by spray drying had spherical shape. The addition of Sc2O3 could decrease the reduction temperature of tungsten oxide. The scandia doped tungsten powder had sub-micrometer size in the range of 0.1 to1 μm and scandium distributed evenly in thepowder. By using this kind powder, sub-microstructure cathode matrices with semispherical grains and homogenous distribution of scandium were obtained.

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Tungsten oxides nanostructures have exhibited application perspectives in such fields as electrochromic (EC) device, photocatalysis, gas sensing, adsorption of organic dyes, etc. So far, in most high-temperature-reaction fabrications of the tungsten oxide nanostructures, the reactant sources and the substrates are separated. Occasionally, tungsten oxide nanostructures are grown directly from the metallic tungsten, which serves as both the reactant source and the substrate. Liu et al. obtained tungsten trioxide (WO3) nanowires by heating a thin W filament in vacuum with some air leakage. Quan et al. developed a single-step route for the direct growth of monoclinic WO3 nanobelt arrays by heating a W sheet without additional catalysts or reactants. The advantages of this direct heating method include short fabrication time, convenient manipulation, less expensive instrumentation and easy accession to high reaction temperatures. Most importantly, tungsten oxide nanostructures can grow directly from, instead of depositing on, the substrates. Therefore, a number of desired properties, such as good adhesion and low contact interface resistance, can be expected.

As previously reported, in this laboratory a fast heating chemical vapor deposition (CVD) system was developed, in which the temperature of the carbon substrate could be raised to 1800°C in 15 seconds with the passage of large electric current. Combined structures of conical carbon fiber and carbon nanotube (CCF/CNT), which had large length, good straightness and perfect crystallinity, were fabricated using this system. Recently, tungsten oxide nanostructures were also attained with similar instrumentation. This paper describes the fabrication process, characterization and field emission properties of these tungsten oxide nanostructures. In terms of heating uniformity, a Wfilament is apparently more controllable than a W foil when used as the directly heated substrate. However, since some applications, e.g., field emission and dye adsorption, require relatively large-area arrays of tungsten oxide nanostructures, W foils were deliberately used in this work.

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Tungsten oxide,  WO3, is a chemical compound containing oxygen and the transition metal tungsten. It is obtained as an intermediate in the recovery of tungsten from its minerals.Tungsten ores are treated with alkalis to produce WO3. Further reaction with carbon or hydrogen gas reduces tungsten trioxide to the pure metal.

The effect of phase composition o f tungsten oxide on the homogeneity of ultrafine tungsten powder has been studied using a conventional hydrogen reduction technique. The results show that ultrafine and homogeneous tungsten powder can be produced from sing le-phase tungsten oxide. The tungsten powder made by multi-phase oxides may be fine , but not homogenous due to differences between the reduction rates ( or reduction paths) of various oxides.

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Tungsten oxide, also known as tungsten trioxide or tungstic anhydride, WO3, is a chemical compound containing oxygen and the transition metal tungsten. It is obtained as an intermediate in the recovery of tungsten from its minerals.Tungsten ores are treated with alkalis to produce WO3. Further reaction with carbon or hydrogen gas reduces tungsten trioxide to the pure metal.

Tungten trioxides and tungsten trioxide hydrate were synthesized via mixing tungsten with H2O2 in a water bath. Samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, cyclic voltammetry. The UV-visible photo activity was ebaluated through the photo degradation of methyl orange in aqueous solution. The effects of photoreaction conditions on the  photo activity of the obtained samples introduce in detail. Cyclic voltammetry measurements showed that WO3·0.33H2O, WO3·H2O and WO3 have different oxidation-reduction potential, that lead to a higher conductive band of WO3·0.33H2O than H/H2. The experimental indicanted that photoactivity of WO3·0.33H2O was deeply related with the crystal structure and energy band structure.

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