Tribological enhancement of CrN coatings by niobium and carbon ion implantation

Metal plasma ion implantation has being successfully developed for improving wear, corrosion and physical properties of engineering materials. In this study, Nb and C ions were co-implanted into CrN films using a metal-plasma ion implantation apparatus. The accelerating voltage of metal ions were set at 50 kV with implantation doses of 5×1016 ions/cm2 for Nb and 1×1017 ions/cm2 for carbon. The mechanical properties of Nb-ion implanted CrN were improved by the presence of CrNbN phases, which lead to the increase of microhardness from 18 GPa of CrN films to 35 GPa. The microhardness was further increased to 55 GPa by sequentially implantation of Nb and carbon ions. The strengthening mechanism was attributed to the formation of chromium carbides along with CrNbN. The wear failure of CrN was caused primarily by chipping between the hard ion-implanted layer and the CrN layer. Results of this study demonstrate the potential of metal plasma ion implantation in improving the mechanical behavior of the CrN film without hampering its tribological properties.