Dose and dose rate effects on the structure of methane plasma source ion implanted 304 stainless steel

Type 304 stainless steel was treated by methane plasma source ion implantation. The effects of implantation dose and dose rate on the microstructure have been investigated. The implantation was carried out at a target bias of −30 keV. Two different doses: 1.5 × 10 17 and 3 × 10 17 atoms cm −2, and three dose rates: 3.4, 6.8 and 15 μA cm −2 were used. Higher doses and lower dose rates favor the formation of crystalline structure in the form of Fe 2C (at 3.4 μA cm −2), or a mixture of Fe 2C and possibly Fe 3C and/or (Fe, Cr) 7C 3 (at 6.8 μA cm −2). Higher dose rates and lower doses favor the development of an amorphous structure. The mechanism of phase transformation in the implanted layer and its dependence on dose and dose rate are discussed.