METHOD FOR NITRIDING CORROSION-RESISTANT AND HIGH-ALLOY STEELS Russian patent published in 2021 - IPC C23C8/26 

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, namely to thermochemical treatment of steel surfaces, and can be used in mechanical engineering for strengthening machine parts made of corrosion-resistant and high-alloy steels. The method for nitriding corrosion-resistant and high-alloy steels includes heating the products in an ammonia stream, sustaining in a mixture of ammonia and air in two stages. At the first stage, heating is conducted to a temperature of 500 to 540°C, and at the second to a temperature of 550 to 600°C with a degree of dissociation of ammonia of 30 to 50%. Additionally, at a temperature of 550 to 600°C, a third stage is executed of sustaining for at least 2 hours only in an ammonia stream with a degree of dissociation of ammonia of 70 to 90%. At the first stage, sustaining is executed for at least 3 hours in a mixture containing 20 to 60% vol. of ammonia and 40 to 80% vol. of air. At the second stage, for at least 3 hours in a mixture containing 60 to 40% vol. of ammonia and 40 to 60% vol. of air.

EFFECT: plasticity of the nitrided layer is ensured due to the reduction in the brittleness and hardness thereof.

1 cl, 4 dwg, 2 tbl, 1 ex