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Gas sulfonitriding

Gas sulfonitriding is a modern thermo-chemical method used for the treatment of steel and cast-iron machine elements and tools. The sulfonitride process is carried out in retort furnaces in an ammonia and sulphur vapour atmosphere at temperatures of  773-973 K, for ten minutes to several hours. As a result of this treatment the friction coefficient of surfaces is low, wear resistance is high and their resistance to seizing is complete. The sulfonitriding process is the final one and the treated elements do not need subsequent mechanical working.

Technology application

Using the method of gas sulfonitriding low-, medium- and high -carbon steels may be treated, as well as low-, medium- and high -alloy steels and cast iron. The technology is recommended for treating machine parts and mechanisms which work in conditions of dry or mixed friction, such as:

  • Cylinder liners
  • Slide bearings
  • Shears
  • Sliders
  • Car mechanisms
  • Worm wheels
  • Injection moulds and many others

Results of the test of seizure resistance:

Tempered steel                              Spheroidal pearlitic                    Constructional steel after                                                          cast iron                                    gas sulfonitriding process

Particular advantages of the sulfonitriding process:

  • It enables to form the surface layer with demanded properties
  • The layers created in the process preclude seizure of mating parts
  • The process warrants high durability of the treated elements
  • Decreases co-efficient of friction
  • Increases resistance against corrosion
  • Increases fatigue strength of steel substrate
  • The offered technology reduces the production and operating costs

Qualities of sulfonotrided layer

Thanks to their complicated structure the sulfonitrided layers fulfill two main functions. The first one is the weakness of adhesive relation of frictional stream elements and decrease of endurance on cutting of unevenness of surface. The other one is the possibility of transfer in zone of point of contacts the pressures in consequence of raised surface layer.

The structure of chromium constructional steel after sulfonitriding process (mag. x 400)

The structure of spheroidal cast iron after sulfonitriding process (mag. x 400)

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