Nanostructured Wc Preparation Process And Its Nanocrystalline Alloys Trial,

Cemented carbides, well known as "the teeth of the industry", were widely applied in many fields of industry. The development of ultra-fine /nanocystalline cemented carbides is the main trend of cemented carbides areas, and the nanometer WC powder is the important raw material of ultra-fine /nanocystalline cemented carbides. The ultra-fine /nanocystalline WC and Co powders should have high-purity, uniform particle size and fine granularity. Nowdays, it is widely reported about preparation of ultra-fine /nanocystalline cemented carbide, but few of these methods could produce at a commercial scale because they have complex technology, high cost of production, more impurity and low efficency. This article is about the preparation of nanometer WC powder. In experiment, nanometer tungsten powder as the raw material and compared five raw materials of carbon black, such as nanometer carbon, activated carbon, ultra-fine carbon, industry carbon. Moreover, carburizing temperature , carburizing time, mode of blend, type of boat and thickness of bed of materials are stydied in detail.The phase and grain size are tested by means of XRD, and the uniformity and microstructure of WC powders are investigated by means of SEM, TEM and BET. Composition analysis instrument test Ct and Cf of the ultra-fine /nanocystalline WC powders. Furthermore, the microstructure and mechanical properties are tested by means of OM, SEM, electronic tensile testing machine and hardness machine. The following results are obtained:1.Orthogonal experiment and range analysis result indicated that particle size of WC powder are connected with type of cabon black,. The more finer of carbon blacd, the particle size of WC is moe finer. Moreover, the type of carbon have an effect on carburizing temperature.2. Comparing with the traditional rolling blend, it is concluded that the three-dimensional blend has higher efficiency and make the compounds more uniformity. The rolling blender need 6 hours make the compounds uniformity, but the three-dimensional blender only need 2 hours.3. Type of boat and thickness of bed of material have obvious effect on the specific area of WC Powder. The WO powder preraed by graphite boat have higher specific area than that by non-corrosive steel boat at the same carbonization process. Moreover, the thickness of bed of material more higher, the specific area of WC is more lower.4.The prepared WC by means of H₂ atmosphere have more higher specific area and the carburizing temperature is lower by contrast with vacuum carburization jprocess. This phenomenon is connected woth free carbon which is decomjposed by carbon-containing atmosphere at elevated temperature. It is concluded that carbon-containing atmosphere affect the the specific area of WC.5. It is possible to prepare nanocrystalline tungsten carbide whose grain size is about 200～300nm. It is very inprotant to avoid oxygen content increase during preparation of the ultra-fine /nanocystalline cemented carbide. The oxygen would result in formation of r| phase and impair physical and mechanical properties of cemented carbide. Adding proper carbon during process of blend is a good way to resolve the question.