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The paper examines the advanced method of spark erosion for recycling hard-alloy scrap. It is shown that spark discharge over hard alloy in water leads to the decarburization of the initial WC phase in the surface layer and of the powder formed. After carburization, the powder can be used for the production of hard alloys. The structure and mechanical characteristics of the hard alloy made of the powder are studied. INTRODUCTIONTungsten carbide-cobalt hard alloys are widely used in modern industry in metal cutting, drilling, and woodworking. The world production of cutting tools was estimated at 2 billion dollars in 1992. About 60% of the total tungsten production is used to produce carbides for cutting tools.The great demand for tungsten and cobalt and the depletion of standard-quality raw materials cause 20-50% annual increase in prices. Hence, there is a need to find ways to recycle hard-alloy scrap.Grinding (dispersion) is the most complicated, labor-and energy-intensive operation in the regeneration of hard alloys. Spark erosion is one of the most promising methods to produce powder from lump scrap. B. R. Lazarenko and N. I. Lazarenko were the first to propose the method in 1943 [1]. It attracted much interest in the sixties-eighties since it involved no mechanical wear of equipment, any conducting materials could be disintegrated, and powder could be obtained in one operation [2][3][4][5].In view of the new trends in materials science, spark erosion is regarded as a method of producing nanocrystalline [6-8] and amorphous [9, 10] powders. Nevertheless, this method is not used to process hard alloys. All publications on spark erosion of various materials focus on research into the structure and chemical, grain-size, and morphological composition of the powder produced. In particular, it is noted in [11][12][13][14][15][16] that the grinding of hard alloys results in powders with modified phase and chemical composition and structure. We are aware of no research papers that would focus on the production of compact materials from dispersed powders. It is still to be decided how to produce hard alloys from spark-eroded powders.The objective of this paper is to optimize the spark-erosion conditions for hard alloys based on research into chemical, phase, and structural transformations that occur in the dispersion and further processing of the powder obtained. SPARK EROSION THEORYThe spark-erosion method is based on the erosion of a material caused by breakdown of a liquid dielectric. Zolotykh's thermal theory states that a gas bubble forms around the discharge channel after breakdown of a liquid dielectric (Fig. 1). The anode material rapidly heats up, melts, and partially boils. After the discharge stops, the gas bubble pulsates several times and collapses. The molten material is thrown from the craters into the interelectrode gap, cools down at a rate of 10 6 -10 9 deg/sec, and solidifies forming particles. At the same time, thermal stresses and pressure in the discharge channel (P ≤ 280 MPa) destruct the surface...

621.762Layered composite materials based on hard alloys grades VK and TK with graded surface properties are studied. The materials are prepared using standard procedures of thermal diffusion impregnation, deposition from the vapor phase, and ion-plasma deposition. In addition dispersion strengthened hard alloys are prepared by processing in Ti plasma between the stages of preliminary and final sintering.