METHOD FOR SULPHOCYANIDING OF STRUCTURAL AND TOOL STEELS IN HIGHLY ACTIVE PASTE Russian patent published in 2019 - IPC C23C8/72 

FIELD: machine building.

SUBSTANCE: invention relates to machine building, particularly, to chemical-thermal treatment of metals and alloys, and can be used for surface hardening of parts of machines and equipment operating in conditions of friction at high contact loads and with lack of lubrication. Method of sulphocyanating articles from structural or tool steels in high-active paste involves depositing highly active paste on the surface of articles, heating with subsequent holding and cooling. High-active paste is paste containing ferricyanide potassium K₄Fe(CN)₆, carbamide (NH₂)₂CO, sodium carbonate Na₂CO₃, sodium sulphide Na₂S, nitrocellulose varnish NC 222 and soot DG-100, with the following ratio of components, wt. %: K₄Fe(CN)₆ – 8–15, (NH₂)₂CO – 5–10, Na₂CO₃ – 5–10, Na₂S – 2–5, nitrocellulose varnish NTs 222 – 15–30, soot DG-100 – balance. Heating is carried out at 550–650 °C with curing for 3 hours, after cooling of item is washed in hot water at temperature 80 °C till the paste is completely removed, dried, then transferred into a bath with hot oil having temperature of 110–120 °C and held for 5–10 minutes.

EFFECT: higher rate of sulphocyanation, possibility of processing articles of any size and shape, possibility of local sulphocyanation of working surfaces of articles, as well as high environmental safety of sulphocyanation.

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