Effect of Annealing on the Surface Hardness of High-Fluence Nitrogen Ion-Implanted Titanium

Commercially pure titanium grade II was kinetically nitrided by implanting nitrogen ions with a fluence in the range of (1-9)·10¹⁷ cm^-2 and ion energy of 90 keV. Post-implantation annealing in the temperature stability range of TiN (up to 600 °C) shows hardness degradation for titanium implanted with high fluences above 6·10¹⁷ cm^-2, leading to nitrogen oversaturation. Temperature-induced redistribution of interstitially located nitrogen in the oversaturated lattice has been found to be the predominant hardness degradation mechanism. The impact of the annealing temperature on a change in surface hardness related to the applied fluence of implanted nitrogen has been demonstrated.