Characterization of complex (B+C+N) diffusion layers formed on chromium and nickel-based low-carbon steel

摘要

Combined surface hardening with boron, carbon and nitrogen was used for low-carbon chromium and nickel-based steels. The microstructure, boron and nitrogen contents, carbon profiles and chosen properties of borided layers produced on the carbonitrided steels have been examined. These complex (B + C + N) layers are termed borocarbonitrided layers. Gas boriding applied to these steels that have been previously carbonitrided enables the production of wear-resistant diffusion layers. After combined surface hardening with boron, carbon and nitrogen in the microstructure two zones have been observed: iron borides (FeB + Fe2B) and carbonitrided zone. The iron borides show the tendencies towards lose of the needle-like nature. Although borocarbonitriding causes reducing of the depth of iron borides zone, it also reduces the microbardness gradient across the case. Probably, the brittleness of borocarbonitrided layer is lower. In the consequence, the frictional wear resistance of borocarbonitrided layers is essentially higher than that obtained in case of only borided layers. The similar values of wear intensity factors are characteristic for borocarburized layers. The carbonitriding used before boriding make possible the application of lower temperature and shorter time in comparison with carburizing process. (C) 2003 Elsevier Science B.V All rights reserved. [References: 21]