OBRABOTKAMETALLOV Vol. 23 No. 3 2021 MATERIAL SCIENCE EQUIPMENT. INSTRUMENTS 6 4 4 Fig. 5. Results of elemental analysis of a section of the microstructure of a sample of conventional hard alloy VK10 (90 %W; 10 % Co) Fig. 6. Cleavage surface of a sample of conventional hard alloy VK10 (90 %W; 10 % Co) Fig. 7. Fracture surface of a sample of conventional hard alloy VK10 (90 %W; 10 % Co) Improvement of the technology for producing bit teeth To achieve high purity and homogeneity of the VK10 (90 %W; 10 % Co) alloy for drilling bit teeth, the technological parameters for obtaining high-purity tungsten metal powder were developed and tested. For this purpose, the technology of obtaining initial tungsten trioxide of high purity was developed. The description of the technology was provided in earlier works of the authors [18, 19]. Fig. 8 presents a micrograph of the tungsten trioxide powder, consisting of homogeneous prismatic crystals. The elemental composition is characterised by the presence of tungsten and oxygen. The ratio of these elements corresponds to the stoichiometry of the trioxide. Fig. 9 shows a micrograph of crystals of the tungsten metal powder, obtained from pure tungsten trioxide. Fig. 9 provides the results of the elemental analysis of the crystals of the obtained tungsten metal powder. Fig. 10 shows the results of the elemental analysis of a sample of synthesised pure metallic tungsten powder, confi rming its high purity. Pure metallic tungsten powder was used to obtain tungsten carbide by the method of carbidization, using graphite powder according to the technology of NPO AGMK. The pure metallic tungsten powder with the W content of more than 99.80 %, i.e. corresponding to the KS grade, was used. The reduction was carried out according to the mode of obtaining its carbide powder, with an average Fischer grain size
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