Obtaining of WC–Co- and WC–TiC–Co-Based Ultradispersive Alloys Modified with B₄C–TiB₂ Quasieutetic

Abstract

Tungsten carbide WC-based materials characterized by high hardness and wear resistance have long been widely used in manufacturing cutting and mining tools. They are alloyed or modified with different ceramic phases to improve operational characteristics further. There are obtained the hard tungsten carbide–cobalt WC–Co and tungsten carbide–titanium carbide–cobalt WC–TiC–Co metal-ceramic alloys ultradispersed powders modified with quasieutectic ceramic alloy B₄C–30wt.%TiB₂ and complex samples compacted from them. The quasieutectic alloy used as a modifier has almost as high hardness as pure boron carbide. Still, it is characterized by higher electrical and thermal conductivities of several orders of magnitude. Two groups of hard alloys modified with B₄C–30wt.%TiB₂ were studied: ВK8 grade WC–Co and T30K4 and T15K6 grades WC–TiC–Co. Metal-ceramic composite powders of different concentrations are obtained by chemical synthesis and mechanical dispersion in an attritor. The particle size of chemically synthesized composite powders is ≤0.3 μm, and those obtained by mechanical dispersion are ≤0.8 μm. SPS (Spark-Plasma Sintering) and HTS (High-Temperature Sintering) methods compact these powder materials. Phase composition of the obtained materials, distribution of chemical elements in them, and structural features are investigated by the XRD (X-Ray Diffraction) method and EDX (Energy Dispersive (micro)X-ray) spectrometry and optical and electron microscopies, respectively. Key physical-mechanical characteristics of the received samples, such as hardness, microhardness, and bending strength, are studied. Ultradispersed (≤0.8 μm) metal-ceramic alloys of the WC–Co–B₄C–TiB₂ system with interesting characteristics have been obtained using the WC–Co hard alloy of BK8 grade as the matrix. A SPS-compacted sample's hardness, microhardness, and bending strength are 93.0 HRA, 3350 kgf/mm², and 100 kgf/mm², respectively. Among the WC–TiC–Co system materials, the Т15K6 grade-based hard alloy modified with 15wt.%(B₄C–30wt.%TiB₂) has the best characteristics with hardness, microhardness, and bending strength of 91.5 HRA, 2900, and 117 kgf/mm², respectively. A preliminary study of the problem of environmentally safe utilization of tungsten-containing scrap and tungsten waste is also carried out as part of the work. In particular, the tungsten heater waste is treated in hydrogen peroxide, and by adding specific liquid components to the tungsten-containing proper solution in a single utilization–synthesis cycle, the target product – ultradispersed WC–Co hard alloy is obtained.