Tribological Characteristics of Nitrogen (N+) Implanted Iron

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Abstract
The effect of implantation of nitrogen ions (1.5 MeV) on the friction and wear characteristics of pure iron sliding against M-50 steel (unimplanted) was studied in a pin-on-disk sliding friction apparatus. Test conditions included room temperature (∼25°C), a dry air atmosphere, a load of ½ kg (4.9 N), sliding velocities of 0.043 to 0.078 m/s (∼15 to 25 rpm), a pure hydrocarbon lubricant (n-hexadecane), or a USP mineral oil and nitrogen ion implantation doses of 5 × 1015 and 5 × 1017 ions/cm2. No differences in wear rates were observed in the low-dose (5 × 1015 ions/cm2) experiments. In the high-dose experiments (5 × 1017 ions/cm2), small reductions in initial (∼40 percent) and steady-state (∼20 percent) wear rates were observed for nitrogen-implanted iron riders as compared with unimplanted controls. No differences in average friction coefficients were noted for either dose. Auger electron spectroscopy combined with argon ion bombardment revealed a subsurface Gaussian nitrogen distribution with a maximum concentration of 6 atomic percent at a depth of 8 × 10−7 m (0.8 μm). Similar analysis within the wear scar (∼2.0 × 10−5 m subsurface) of an implanted rider after 20 μm of wear yielded only background nitrogen concentration. No inward migration of nitrogen ions was observed.