Diffusion and micro-alloying mechanism of rare earth (RE) and carbon/nitrogen atoms permeated into surface layer of steel during RE-carburizing, -nitriding and -nitrocarburizing

According to the authors' achievements in RE thermochemical treatment field, the defect theory of solid physics, the diffusion theory, the precipitation theory of secondary phase and the grain refining and ultra-refining theory were combined together based on the classical thermochemical treatment theory. A novel RE thermochemical treatment theory including a new diffusion model has firstly put forward resulting from an establishment of Cottrell atmosphere composed mainly of RE atoms and interstitial atoms such as carbon and nitrogen. A new technical system about new RE-carburizing, -nitriding and -nitrocarburizing of steels was constructed. The application of the new system not only obviously increases the diffusion rate, but also significantly improves the microstructure and service performances. Thus the service life of the parts such as gears treated by the new technologies mentioned above can be prolonged remarkably.