**4. Conclusion**

16 Tungsten Carbide – Processing and Applications

treatment: A – T=85ºC; B – T=145ºC.

Bending strength, σ,

Percentage of particles less

process.

**Figure 8.** Dependence of refined tungsten carbide powder microstructure on the terms of ultrasound

(a) (b)

**Figure 9.** Particle size distribution of tungsten carbide powder synthesized in industrial reactor.

Density, g/cm3 14.9 14.7 Hardness, HRA 91 90.5 Coercivity, A/m 270 280

kg∙f/mm2 170 130

Durability coefficient 1.4 1.0 Porosity, A % 0.04 0.2

than 1 μm in size 80 % 60 %

**Table 5.** Physicochemical properties of WC-Co alloys prepared by using WC-SHS and WC-furnace

**Parameters SHS WC alloy VK6-OM alloy (standard)** 

The processes of Self-propagating High-temperature Synthesis were studied for obtaining nanosized powders of refractory compounds, particularly, tungsten carbide. The SHS terms influence crystallization of the obtained powders. Varying the SHS parameters (reactant ratio, regulating additives, inert gas pressure, combustion and cooling velocities) allows changing tungsten carbide powder morphology and particle size.

SHS tungsten carbide powder differs from its furnace and plasmochemical analogs in structure and purity. The grain size can be governed during the SHS processes. Powders of less than 100 nm in particle size can be obtained at complete suppression of recrystallization in combustion products. Separation of the powders from the milled cakes by chemical dispersion with various solutions and choice of chemical dispersion terms (the solution composition, the process time and temperature) allow obtaining SHS materials with the nanostructure characterized by high specific surface area and particle size less than 100 nm with simultaneous preserving the phase and chemical composition of the product.

As a result of the realized research, the technology of Self-propagating High-temperature Synthesis has been developed for production of ultrafine and nanosized tungsten carbide powder with the use of chemical dispersion for separation, purification and additional milling of the target product. The sinterability of the synthesized tungsten carbide powder was studied. The bending strength, durability coefficient, and dispersion degree of WC-Co alloy produced from SHS tungsten carbide exceed those of the commercial alloy.

The proposed technology of ultrafine and nanosized tungsten carbide powder synthesis has some advantages in comparison with the available technologies:

	- Availability of theoretically explained backgrounds for governing the reaction temperature and velocity and component conversion completeness, which provide the possibility of obtaining high quality products of the preset structure at optimum terms;

Self-Propagating High-Temperature Synthesis of Ultrafine Tungsten Carbide Powders 19

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Nowadays, the number of ultra-dispersed materials produced in industry is restricted. Development of industrial production technologies and widening of application fields of nanosized materials is commercially important.
