Study of W-C system alloy obtained from scheelite concentrate by local high-energy impact method
The purpose of the paper is to study the chemical and physical properties of a hard alloy obtained from tungsten-containing multicomponent mineral raw materials of the far East region by the method of local high-energy impact of the flow of ionized plasma, the specific power of which is > 10<sup>4</sup>-10<sup>5</sup> W/cm<sup>2</sup>. The methods of X-ray phase and spectral microanalysis, as well as scanning electron microscopy are used to study the chemical composition of W-C system alloy samples. The PMT-3M microhardometer is used to determine the microhardness. The Ntegra Prima modular atomic force microscope is used to determine the nanohardness of the alloy phases. The chemical elemental and phase compositions of samples of the W-C alloy obtained by the method of local high-energy impact on the charge consisting of scheelite concentrate and graphite are studied. Consideration is given to the experimental dependences of the amount of obtained tungsten carbides on the temperature of the plasma flow Tp and its action time τ in the synthesis chamber, as well as on the amount of graphite introduced. The results of spectral and scanning electron microscopy of alloy samples are examined. The values of microhardness and nanohardness of the resulting alloy of the system W-C are determined. Laboratory tests of experimental alloy samples have revealed that the alloy is a solid solution mainly composed of two phases: WC and W<sub>2</sub>C. The obtained solid solution of W-C system features a high hardness (Vickers hardness number is from 13 to 20 GPA) and wear resistance. The study results of the phase composition of the W-C system solid solution and its structure suggest that the solid ‘skeleton' of the WC carbide phase is intertwined with the ‘skeleton' of the W<sub>2</sub>C phase. The prospects of the method of plasma-chemical synthesis of tungsten carbides from scheelite concentrate for obtaining a solid solution of the W-C system are estimated.