The phenomenon of first order grain boundary phase transitions with formation of a two-dimensional liquid phase in the range of 0.55–0.86 of metal melting temperature is used for developing thermochemical technology for synthesis of nanosize nitrides using gaseous nitrogen. The theoretical premises of the technology are based on film thermodynamics. A generalized equation obtained is used for calculating the phase transition temperature, i.e., grain boundary melting for a number of metals, and development of a strategy for effective coating formation by synthesis of nanosize nitrides and carbonitrides in surface layers of hard metals and alloys. Formation of an overall nitrogen concentration gradient from 4 to 0.5 at.% within surface layers (up to 3 mm) of hard alloys leads to formation of modified coatings with a stepped change in properties. WC–Co and WC–TiC–Co tool hard alloys and chromium tool steels are used in experiments. Industrial testing shows an increase in tool strength and wear resistance by not less than a factor of 1.5–3.
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Translated from Metallurg, No. 11, pp. 26–33, November, 2011.
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Minaev, Y.A. Thermochemical nanotechnology in metallurgy and machine building. Metallurgist 55, 771–779 (2012). https://doi.org/10.1007/s11015-012-9501-3
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DOI: https://doi.org/10.1007/s11015-012-9501-3