Surface mechanical properties of C implanted Ni

Abstract

Nickel foils, 165 μm thick, have been carbon implanted at 300 K with 2, 3, and 4.2 × 1017 C ions/cm2 and implanted with a two-step implantation of 2.1 × 1017 C/cm2 at 300 K followed by 2.1 × 1017 C/cm2 at 77 K. All implantations performed at 300 K result in the formation of the metastablc phase Ni3C while the two-step implantation produces an amorphous Ni/C alloy. Surface mechanical property studies showed that both the surface hardness and wear properties are correlated with chemistry (carbon dose), and that the friction coefficient is additionally dependent on the surface microstructure. It was found that both the wear rate and coefficient of friction were reduced as the volume fracion of Ni3C increased. At the highest dose implanted 4.2 × 1017 C/cm7, the coefficient of friction was found to be lower for the sample implanted half at 300 K and half at 77 K and possessing an amorphous structure compared to the sample implanted entirely at 300 K and possessing a crystalline Ni3C structure. Increases in the surface hardness were also observed with increasing carbon content, with the greatest hardness observed in samples implanted to a total dose of 4.2 × 1017 C/cm2. The hardness at this dose was not dependent on the implant conditions or the metastable phase formed.