Thermodynamic aspects of WO3 tungsten oxide reduction by carbon, silicon, aluminum and titanium
The development and research of new materials for machine parts of the mining and metallurgical complex by the method of surfacing with flux cored wire has a lot of attention nowadays. Flux cored wires are widely used for surfacing of steels with high wear resistance, in which reduced tungsten in the form of ferroalloys, ligatures and metal powder of various degrees of purity are used as fillers. However, due to the scarcity and high cost of tungsten, its rational use is an urgent task. For practical application, the technology of surfacing with tungsten-containing flux cored wire is of interest; using it the maximum extraction of tungsten into the deposited layer is achieved due to reduction processes in the arc. In order to increase the beneficial use of tungsten, the technologies of indirect alloying with tungsten during surfacing under the flux of flux cored wires, in which tungsten oxide is used as a filler on the one hand, and reducing agent – on the other, deserve consideration. It can be expected that during arc discharge, tungsten and (or) chemical compounds of tungsten with reducing agents can be formed during the surfacing process. This paper presents the results of a comparative analysis of the thermodynamic processes of tungsten oxide reduction by carbon, silicon, aluminum and titanium during arc discharge occurring during surfacing with flux cored wires under a layer of flux. The thermodynamic analysis of 41 reactions in standard states showed that the presence of reducing agents (carbon, silicon, aluminum, titanium) in the flux cored wire used for surfacing will contribute to the formation of silicides and tungsten carbides, and, possibly, tungsten itself. It was determined that the best state for the participation of tungsten oxide in reactions in the arc is WO3(g) gaseous state.
