[en] The dual ion implantation of silicon and carbon into copper (99.9%), iron (99.9%), SKD11 steel and SUS304 austenitic stainless steels was carried out with a MeV energy ion accelerator. The cross-section of the implanted layer were observed with scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The surface layers of the implanted substrates were investigated with X-ray photoelectron spectroscopy (XPS) and a transmission electron microscope (TEM). The hardness of the samples was tested with a nano-indentation. It was found with XPS Si (2p) spectra and TEM that a part of the Si ions and C ions formed an amorphous layer of SiC, carbide and metals by dual ion-implantation. The hardness of the dual ion-implanted steels were improved. The mechanism of hardness was suggested by cross-sectional TEM images. (author)