Thermal behavior of nitrogen and carbon implanted AISI 304L stainless steel

Abstract AISI 304L stainless steel samples were implanted at room temperature with 100 keV nitrogen or carbon ions with a 4 × 10 17 ions/cm 2 fluence. Samples were annealed at a temperature of 360 °C for 4 and 100 hours. Using the nuclear resonant 15 N (p, αγ) 12 C reaction at 429 keV proton energy, distribution profiles of 15 N were measured for as-implanted and annealed samples. Carbon ( 12 C) depth profiles were determined using backscattering spectrometry with 5.7 MeV He 2+ ions. Conversion electron Mossbauer spectroscopy (CEMS) was used to determine the phases produced by ion implantation and to follow their thermal evolution. Annealings produced a weak loss of nitrogen (10%) or carbon (30%) atoms in the analyzed region together with a deep diffusion of the two species. In the case of C implanted steel, diffusion toward the surface was also observed. CEMS analysis showed that (Fe, Cr) 2 N and (Fe, Cr) x C phases formed after implantation are rather stable even after 100 hours of annealing. The partial dissolution of these phases led to the formation of magnetic components attributed to α'(N) or (C)-martensites. Different thermal evolutions of the C and N implanted 304L surface region were observed. Results point out the stabilizing role played by chromium atoms and a competition phenomenon between the compound growth and the implanted atom diffusion.