Влияние механической активации порошка ВК-8 на свойства спеченных твердых сплавов

Abstract

Introduction. For the manufacture of wearproof tools and machine elements, the method of powder metallurgy is widely used. The preliminary high-intensity mechanical activation of the powder is used to improve the structure and properties of the alloy obtained by the method of powder metallurgy. The mechanical activation can result in formation of nanostructures with subsequent amorphization of the material, can bring phase transformations, it can certainly affect the properties of the material. However, mechanical treatment does not always lead to a positive result. Therefore, the study of the effect of mechanical activation of WC-based powder on the properties of sintered alloys is important. Purpose of the work: to study the effect of high-intensity mechanical activation of WC-based powder on the structure and properties of sintered samples. The work investigates alloys obtained by the method of powder metallurgy, using mechanically activated powders for 10 to 300 seconds in a planetary ball mill. Materials and methods. The alloys are obtained by cold one-sided pressing followed by sintering at a temperature of 1400 °C in a vacuum furnace. Particle morphology of powder and structure of alloys is analyzed by scanning electron microscopy method. The metallographic analysis of the alloys is carried out by optical microscopy. Phase analysis and the parameters of the crystal structure are performed by X-ray diffraction. The hardness of the sintered samples is measured by hardness tester. Results and its discussion. It is shown that after sintering of powders alloys with WC and Co phases are formed. The lattice parameter of the WC-phase correlates well with values in literature. A second carbide phase, Co3W3C, is formed in the samples upon mechanical activation for more than 100 sec. The minimum porosity of sintered sample is 7.8 ± 1 % that corresponds of sample with preliminary mechanical treatment for 30 seconds. It is shown that the hardness depends on grain size, porosity and second carbide content. Thus, mechanical activation can be effective for increasing the physical and mechanical properties and inhibiting grain growth, but in this case, it is necessary to carry out mechanical processing in the mechanical treatment time range 60-100 sec.