Low-temperature carbonitriding of steel combined with quenching of the surface layer

Conclusions

• 1. A new process of combined low-temperature carbonitriding with quenching of the surface layer has been developed to improve the wear resistance of machine parts.

• 2. Carbonitriding is conducted at 690–700°. In the first 2–3 h the surface of the steel is austenitized in a mixture of 5–10% NH₃+90–95% N₂ for carbon and low-alloy steels and in 30% NH₃+70% N₂ for highalloy steels.

  In the following 2–5 h carbonitriding occurs at the same temperature in an atmosphere of carburizing gases and ammonia, followed by quenching in oil.

• 3. After this new treatment of steels 20Kh and 40Kh a diffusion layer 0.4–0.7 mm thick is formed that consists of a carbonitride zone 10–20 μ thick at the surface, a martensite zone with HV 700–800 to a depth of 0.08–0.12 mm, and a transition zone 0.25–0.5 mm deep.