In this study, Fe-1Nb, Fe-5Nb and Fe-10Nb (at.-%) binary alloys were boronized by the pack boronizing method at 950 degrees C for 3 h. The effect on the boride layer of the increasing niobium amount in pure the iron was experimentally investigated. After boron treatment, microstructural changes occurring on the surfaces of the coated alloys were examined by SEM, EDS and XRD analysis. A microhardness test analysis was applied to the coated alloys. Typical saw tooth morphologies were present in all coated alloys. The increasing niobium amount in the pure iron suppressed the appearance of the saw tooth morphologies. In addition, the microhardness of the boron layers was much higher than that of the base metal.