Tribological properties of Fe and Ni base alloys after low energy nitrogen bombardment

In this paper we investigate the influence of a low energy-high flux nitrogen implantation treatment on the structure and tribological properties of two commercial alloys of interest for industrial applications (AISI 316 and INCONEL600). Nitrogen ion implantations were carried out at 400 °C with a current density of 1 mA/cm2, an accelerating voltage of 1.2 kV and a processing time of 1 h. XRD measurements show clearly the presence of an expanded fcc structure in both alloys AISI316 and INCONEL600. The depth profiles measured by GDOS indicate a high nitrogen content on several microns in all these alloys. It is found that the hardness measured under a 2 mN load increases by a factor of 3,4 for AISI316 and 2 for INCONEL600. Friction and wear tests conducted under a normal load of 1 N with tungsten carbide and 100C6 steel balls show no significant change of the friction coefficient whatever the relative humidity during the test but an important wear resistance improvement is observed for both alloys. The results are discussed in relation with the thickness of the nitrided layer and the microstructural modifications induced by this treatment.