CARBIDE AND NITRIDE CARBIDE LAYERS IN IRON SYNTHESIZED BY ION-IMPLANTATION

Stoichiometric iron carbide layers have been fabricated using a t-o-st ep implantation process. First, carbon preimplantation at 400 keV is p erformed at low substrate temperature (approximately 50-degrees-C) to form a region with high carbon concentration. For a pre-implantation d ose of 7.5 x 10(17) cm-2, annealing at 300-degrees-C results in format ion of stoichiometric Fe3C (cementite) at the position of the pre-impl anted atoms. When the pre-implanted specimen is implanted with 850 keV C+ at 300-degrees-C the Fe3C layer grows by diffusion of implanted at oms through the iron substrate to the cementite layer. When a 400 keV carbon pre-implant is followed by implantation of 1 MeV nitrogen at 30 0-degrees-C, gamma'-Fe4N nucleates and grows on the carbide layer.