METHOD FOR CYCLIC GAS NITRIDING OF PARTS FROM HIGH-ALLOY STEELS Russian patent published in 2019 - IPC C23C8/26 B82Y30/00 

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy and machine building, namely to chemical-thermal treatment, in particular to cyclic gas nitriding of high-alloy steels, and can be used in production of parts operating at high temperatures in conditions of friction with large contact loads. Method of cyclic gas nitriding of parts from high-alloy steels involves preliminary application of catalyst coating on surface of part, heating in furnace to temperature of 540–650 °C in atmosphere of ammonia and carbon dioxide with ratio of their volumes of 1:1, isothermal holding at temperature of said heating, during which saturation atmosphere is replaced cyclically in two stages in each cycle, and further cooling together with furnace in ammonia atmosphere. 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. Second stage of said cycle is carried out in a saturating atmosphere of ammonia in a mixture with carbon dioxide at a ratio of their volumes of 1:1. Said cyclic substitution of saturating atmosphere is repeated until nitrided layer of preset thickness is obtained. Catalytic coating used is a slurry coating containing chromium oxide Cr₂O₃.

EFFECT: increased thickness of the diffused nitrogen-containing layer obtained on the surface of parts from high-alloy steels with reduction of duration of the nitriding process and without reduction of its hardness.

1 cl, 3 dwg, 1 tbl