Dose Rate Influence on the Microstructure of Chromium Steels Subjected to Low-Energy Nitrogen Ion Implantation

摘要

X-ray diffraction and optical microscopy were used to analyze microstructure of the surface layer on chromium steels subjected to low-energy, high-current-density nitrogen ion implantation. It was demonstrated that the phases formed are controlled by dose rate, chemical composition, and preceding heat treatment of steels. In the case of quenched steel containing a low chromium content, decreases in dose rate corresponds to a deeper modified layer. For chromium-rich steel, the dose rate did not influence the thickness of the modified layer, but a high dose rate induced more effective hardening of the surface and formation of nitrogen-rich phases. Preceding quenching intensifies diffusivity of nitrogen. The model is presented to explain dose rate, chemical composition and heat treatment influence on the microstructure of the surface.