PLASMA IMMERSION ION-IMPLANTATION OF STEELS

Plasma immersion ion implantation (PI3) is a new technique with certain advantages over conventional ion implantation. We have developed an implanter based on an inductively coupled r.f. glow discharge plasma. Ion densities of 10(10) cm-3 are obtained with filling pressures of about 10(-3) mbar. Ions are accelerated from the plasma by high voltage pulses (typically - 45 kV) applied directly to the work-piece. In this paper we report on the application of PI3 to nitrogen implantation in steels. Dramatic increases in microhardness and wear resistance have been observed for a number of steels, ranging from 0.3 wt.% C mild steel to austenitic stainless steels. Despite the relatively low implantation energy, the modified layer can be greater than 1-mu-m in thickness. The nitrogen concentration profile can be controlled by the implantation temperature and dose. Glancing-angle X-ray diffraction has been used to determine the structural changes that occur in the surface layer.