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The Legal System Of Reaction Heat Treatment Preparation Of Nanocrystalline Wc-co Cemented Carbide Powder

Posted on:2005-10-15Degree:MasterType:Thesis
Country:ChinaCandidate:H Y GaoFull Text:PDF
GTID:2191360125955330Subject:Materials science
Abstract/Summary:PDF Full Text Request
It was found that there exist shortcoming in both chemical method and mechanical method for preparing nanocrystalline cemented carbide powder after a lot of kinds of methods and principles being discussed and compared. Chemical methods always have no broad in production scale and have high manufacture cost. Mechanical methods must need long time in production and the impurities are very easy to sneak into powder .So a new method for production nanocystalline cemented carbide powder has been invented in this experiment .It is mechanical activation-reaction heat treatment. This technology optimized the mechanical method, and avoided the shortcoming in chemical and mechanical method. It is an efficient and potential technology in manufacture nanocystalline carbide powder.In this research,the raw materials tungsten, cobalt and black carbon powders were treated by mechanical activation-reaction heat treatment to prepare nanocrystalline WC-6Co and WC-10Co composite cemented carbide powders. The phase structure change and their contents in each processing stage were systematically investigated using X-ray diffraction technology and DTA .At the same time the grained size was counted in Scherrer formula. It was found the raw materials' X-ray diffraction peakhas obviously widen after mechanical activation for some time. The main phase is W and some W2C phase was synthesized in WC-10Co powder. After heat treatment in different time and temperature, W2C and WC phase were found in the two systems' X-ray diffraction. With the increase of time and temperature , the content of W2C phase decrease and the content of WC phase and the grain size increase. When reaction heat treatment in 850, the W2C decomposed and synthesized into WC. The WC-10Co composite powders with 33.3nm crystal size and the WC-6Co composite powder with 35nm crystal size were produced after heat treatment in 900 for 35min. SME also has been used to examine the composite powder.
Keywords/Search Tags:mechanical activation, reaction heat treatment, nanocrystalline, WC-Co composite powder, grain size
PDF Full Text Request
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