Abrasive wear studies of nitrogen-implanted aluminium and titanium

Disks of commercial grade aluminium and titanium were implanted at room temperature with nitrogen ions to doses ranging from 1 × 10¹⁶ to 5 × 10¹⁷ ions cm^-2. The abrasive wear resistance of the implanted layer was tested using a modified polishing machine. The relative wear resistance (RWR) was measured along the wear depth. For both aluminium and titanium an appreciable decrease in wear rate was observed for sample surfaces implanted to doses higher than 1 × 10¹⁷ cm^-2. The RWR reaches a maximum value of about 4 in the implanted layer close to the sample surface and gradually drops to unity when the implanted layer is removed. X-ray diffraction using Seemann-Bohlin geometry reveals the formation of AIN and TiN in aluminium and titanium respectively after high dose implantation. We attribute the ennoblement of the surface after implantation to the classic hardening mechanisms of solid solution and fine dispersion strengthening. Abrasive wear testing appears to be an appropriate method of evaluating the hardness of the thin surface layer and the effectiveness of implantation.