COMBINED CHEMICAL-THERMAL TREATMENT OF MACHINE PARTS OF HEAT-RESISTANT STEELS Russian patent published in 2014 - IPC C23C8/38 C23C14/06 

FIELD: process engineering.

SUBSTANCE: invention relates to machine building, particularly, to combined chemical and thermal processing of machine parts. Proposed process comprises cyclic cementation of parts and their quenching. Before cyclic cementation preliminary heat treatment and mechanical processing are executed including normalisation at 950°C, high tempering at 670°C, quenching from 1010°C, high tempering at not less than 570°C and plastic upsetting at, at least 700°C at deformation degree of 50…80%. Cyclic cementation is performed with alternation of saturation and diffusion curing, at least 12 cycles of 30 minutes duration. The number of cycles depends on required depth of diffusion ply while saturation-to-curing interval ratio makes 0.1 to 0.2. After said cementation, conducted are high tempering, quenching in oil, cold processing at -70°C and threefold tempering at 510°C. The, ion-plasma nitration is performed in temperature rage of 480…500°C for at least 10 hours at the following parameters: cathode voltage at cathode spraying of 900 V, in saturation mode - 400 V, current density of 0.20…0.23 mA/cm², has medium composition - nitrogen-hydrogen mix with 95% of nitrogen and 5% of hydrogen, gas mix flow rate of up to 10 dm³/h, chamber pressure at cathode spraying - 13.3 gPa, at saturation - 5…8 gPa.

EFFECT: higher surface ply wear resistance, longer life.

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