Dzykovich V. Research and development of the technology for thermal centrifugal spraying of refractory materials based on tungsten carbides WC-W2C, and development of a range of cladding consumables to produce super wear-resistant composite coatings

The thesis is dedicated to research and development of the technology for production of spheroidized granules of tungsten carbides and consumables on their base to deposit wear-resistant composite coatings. The choice of thermal centrifugal spraying of refractory materials using the plasma arc as a heat source was substantiated. Mathematical modeling of the method of thermal centrifugal spraying of tungsten carbides was used to derive appropriate mathematic equations, relating the main process parameters (thermal characteristics of the heat source and rotation speed) to the process productivity (Vfeed) and size of the resulting granules (d). The mechanism of control of size composition of the spheroidized granules of tungsten carbides WC-W2C was developed. The formula for calculation of the speed of rotation of a spindle assembly of the machine was derived to provide the required size composition of the spherical particles. The effect of the quality of spraying ingots on structure, properties and stoichiometric composition of the produced spherical tungsten carbide particles was investigated. It was determined that the use of ingots produced in induction furnaces by remelting provided spherical particles with a minimal deviation from the eutectic composition and with an increased consistency of microhardness and chemical composition values. It was found out by comparing the spheroidized tungsten carbide granules with analogues of the known foreign companies that the particles produced by thermal centrifugal spraying are explicitly advantageous in such characteristics as microhardness and homogeneity of chemical and phase compositions. The effect of the quality of the spraying ingots on structure, properties and phase composition of the spherical granules was investigated by X-ray diffraction, metallography, X-ray microanalysis and energy-dispersive spectral analysis methods. The technology for thermal centrifugal spraying of refractory materials by using the plasma arc as a heat source was developed, and the commercial equipment was built on the basis of theoretical data and experimental proof of the results obtained. The first-ever investigations of morphometric characteristics of the spheroidized granules of tungsten carbides WC-W2C were carried out. The investigations showed that all the powders tested were characterized by a highly consistent and uniform shape of their particles. The cladding consumables were developed to deposit wear-resistant composite coatings based on the spheroidized tungsten carbide granules by different methods. Key words: thermal centrifugal spraying of tungsten carbide ingots, spheroidized granules, morphometric characteristics of powders, cladding consumables, wear-resistant composite coatings.