Influence of high-temperature carbonitriding on the structure, phase composition, and properties of low-alloy steels

1. The limiting condition reached in high temperature carbonitriding of low alloy steel with a high nitrogen content (up to 1.0%) is the formation of ɛ-carbonitride while in carbonitriding with a high carbon content and a low of nitrogen (0.3–0.4%) cementitebase carbonitride is formed. 2. High temperature carbonitriding of austenite alloyed with chromium with high nitrogen potentials occurs according to the mechanism of internal nitriding with the formation of mixed segregations or CrN nitrides. 3. With the optimum ratios of carbon and nitrogen in carbonitrided cases and of residual austenite and martensite in the structure high values of fatigue bend strength of KPP gears (Pmax=47.5 kN) and of contact fatigue life of the cases (Po=1800 MPa) may be obtained.