Hardness and corrosion resistance of single-phase nitride and carbide on iron

With ion beam synthesis, closed homogeneous nitride and carbide layers have been produced. The hardness and the corrosion resistance potential of γ′-Fe4N, ϵ-Fe2.6N and Fe3C cementite single-phase layers have been determined. The results are compared with samples implanted in a conventional way with the same N concentration, resulting in precipitates, and with untreated iron. The hardness is found to be increased by a factor of 2.5 in comparison with pure iron; no significant difference between the different samples is found. In cyclovoltammetric tests, the dissolution of iron is found to be suppressed considerably by three orders of magnitude for γ′-Fe4N, 1.5 for cementite and 1 for ϵ-Fe2.6N, while implantation of precipitates even promotes the corrosion.