EFFECT OF HIGH-DOSE N-2+ ION-IMPLANTATION ON SURFACE CHARACTERISTICS OF AISI-302 STAINLESS-STEEL WITH AND WITHOUT AN INDUCING STRAIN

The effect of nitrogen ion implantation in AISI 302 stainless steel has been examined on two different surface conditions of the substrate such as strain induced (mechanically polished) and excess strain free (chemically etched). Samples were implanted with 2.5 X 10(21) N2+ m-2 at 130 keV. The identification of the phase change and compounds formed was performed by glancing-angle X-ray diffraction. Diffraction patterns were recorded on polished samples prior to and after implantation, with and without chemical etching. The alpha'-martensite phase formed during mechanical polishing is observed on an austenitic substrate. It is completely removed by chemical etching before implantation. After implantation, in polished samples, more alpha'-martensite is observed together with Cr2N and epsilon-Fe2N-Fe3N whereas, in etched samples, only the gamma-austenite phase is observed with Cr2N. The surface hardness is found to be enhanced after implantation in both cases. The possible correlation of the changes observed after implantation with increase in the surface hardness is discussed.