The effect of efficient high-dose-rate plasma immersion ion implantation on microstructure and properties of 8Cr4Mo4V steel

Abstract

8Cr4Mo4V steel was implanted with 20 keV nitrogen ions dose rates with fluences between 2.60 × 1017 ions/cm2·h and 1.04 × 1018 ions/cm2·h. The samples were analyzed by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), elemental dispersive spectroscopy (EDS), secondary ion mass spectroscopy (SIMS), auger electron spectroscopy (AES) and nanoindentation test. The stopping and range of ions in matter (SRIM) code was used to calculate vacancies and displacements distributions. The results reveal that the implanted surface layer contains the phase composition of Fe(M) and Fe2–3N. The peaks of the samples with a dose rate from 2.60 × 1017 to 7.85 × 1017 ions/cm2·h are broadened and slightly shift to left by 0.777° towards comparing to the dose rate of 1.04 × 1018 ions/cm2·h. A significant improvement in roughness of Ra (∼10.4 nm) is attained for the dose rate of 7.85 × 1017 ions/cm2·h. The lattice parameters of the smallest grain size, the highest micro-strain and dislocation density of 11.78 nm, 7.716 × 10−3 and 1.559 × 1016 /m2 respectively were obtained for the dose rate of 5.18 × 1017 ions/cm2·h. There exists a deep diffusion zone of about 400 nm for the dose rate of 7.85 × 1017 ions/cm2·h and 1.04 × 1018 ions/cm2·h, which is 4 times deeper than other implanted samples. Furthermore, the nanohardness of implanted samples improved notably as well, especially at the dose rate of 8.64 × 1017 ions/cm2·h, reaches to a higher value of 16.3 GPa, which is 46.8 % higher than that of non-implanted sample of 11.1 GPa, implies that the properties of samples strongly affected by the implantation dose rate.