Plasma processing for surface modification of trivalent chromium as alternative to hexavalent chromium layer

Plasma source ion implantation (PSII) treatment was undertaken to improve the mechanical properties of electrodeposited trivalent chromium layers. Nitrogen ions were implanted, with energies of − 15 to − 25 keV and doses of 1, 5 and 10 × 1017 atoms cm− 2, to modify the surface properties of Cr plating layer. The surface properties of the films were characterized by XRD, SEM, ruby-ball on disk type tribometer and nanoindenter. Polycrystalline CrN films with (200), (220) and (222) orientations were preferentially grown and numbers of surface cracks were increased by N+-PSII onto trivalent chromium layers. The surface hardness of the Cr3+ plating layer was increased from 16 to 25 GPa by N+-PSII. Severe wear and higher friction was observed on N+-PSII treated trivalent Cr plating. It seemed that the wear debris from hardened and cracked surface of the N+-PSII treated specimen prompted abrasive wear in the wear test. Roughness of the Cr3+ plating layers was smoothed with increasing implantation doses.