METHOD FOR CYCLIC NITRIDING OF ARTICLES MADE FROM STEEL 08U IN GASEOUS MEDIA Russian patent published in 2019 - IPC C23C8/26 B82Y30/00 

FIELD: technological processes.

SUBSTANCE: invention relates to chemical heat treatment, namely, to gas nitriding of steels using nanotechnologies, and can be used in machine building, instrument making and other industries. Method for cyclic nitriding of articles from 08U steel in gaseous media involves depositing a copper-containing nanoparticle layer on a surface of articles as a catalyst, subsequent heating of articles n in furnace in atmosphere of ammonia and carbon dioxide to saturation temperature of 540–650 °C, followed by isothermal exposure, during which saturation atmosphere is replaced cyclically in two stages in each cycle. First stage of the isothermal holding cycle is carried out in a saturating atmosphere of ammonia in a mixture with water vapor at a ratio of volumes of said components of 1:1, and the second step of said cycle is carried out in a saturating atmosphere of ammonia in a mixture with carbon dioxide at a ratio of volumes of said gases of 1:1. Said cyclic replacement of saturating atmosphere is repeated until nitrided layer of specified thickness is obtained, after that, products are cooled together with furnace. At the preliminary stage, a layer of copper-containing nanoparticles in the composition of the nanocomposite combined with macromolecules of the polymer pseudomatrix with further drying of the layer with formation of the nanostructure is applied on the surface of steel articles by dipping. Prior to beginning of said heating in atmosphere of ammonia and carbon dioxide, copper-bearing nanoparticles have spherical shape and diameter of 3–15 nm, and after said heating and decay of polymer pseudomatrix form on surface of articles copper-containing layer consisting of discrete particles located at a distance from each other. In particular cases, poly-N-vinylpyrrolidone with different molecular weight is used as polymer pseudomatrix. Copper-containing nanoparticles used are copper or its oxides.

EFFECT: intensified process of nitriding, as well as obtaining on steel surface uniform reinforced layer with increased thickness of monolithic zone of cermets while maintaining high strength characteristics.

3 cl, 9 dwg, 1 tbl