Effect of pulse bias voltage and nitrogen pressure on nitrogen distribution in steel substrate by plasma immersion ion implantation of nitrogen

Nitrogen ions were implanted into low carbon steel under various pulse bias voltage and pressure in order to investigate nitrogen distribution by using a plasma immersion ion implantation (PIII). A beam-line implanter was also utilized to compare the implanted nitrogen distribution between two approaches. The nitrogen-implanted surface was characterized by X-ray diffractometer (XRD) for identification of in-situ synthesized nitride. Auger electron spectroscopy (AES) was used to determine the depth profile of the implanted nitrogen. Substrate temperature was estimated from the hardness of tool steel substrate treated simultaneously. Formation of Fe₃N and Fe₄N were recognized in the near-surface region of the substrate. Nitrogen concentration reached 25-30 mol% at the surface, and reduced with increasing depth. Nitrogen-affected region became deeper with bias voltage and nitrogen pressure. Maximum distribution depth of nitrogen correlated with the bias voltage and the substrate temperature.