Influence of the structure of a carbonitrided case on the properties of constructional steels

Conclusions

• 1. Carbonitriding at 700°C in atmospheres of ammonia and carbon-containing components (endogas or natural gas) makes it possible to obtain a high-quality carbonitride (oxycarbonitride) case containing 3–4% N in the dense zone and 0.5–1% in the porous zone 0.5–1.0% C, and up to 3.5% 0, an austenitic-martensitic sublayer containing 1.0–0.6% N and C and 0 at the level of the matrix, and a lower-lying layer of a solid solution of nitrogen in α-Fe.

• 2. Carbonitriding at 700°C promotes a significant increase in wear resistance of constructional steels. In this case the coefficient of sliding fraction in tests without lubricant was 0.20–0.23, the fatigue limit in bending increases by 1.7 times in comparison with the normalized condition, and the corrosion resistance increases by an average of 10 times.