NITROGEN AND BORON ION-IMPLANTATION INTO ELECTRODEPOSITED HARD CHROME

Electrodeposited hard chrome has been ion implanted with nitrogen alon e, boron alone, and a combination of nitrogen and boron. Separately, n itrogen and boron implantation was carried out at 75 keV and incident doses of 2, 4 and 8 x 10(17) at cm(-2). Samples implanted with both ni trogen and boron used beam energies of 75 keV and incident dose levels of 4 x 10(17) N-at cm(-2) and 4 x 10(17) B-at cm(-2). All ion implant ations were accomplished using a beam-line system. The retained dose w as measured using ion beam analysis. Surface hardness, wear coefficien t and the coefficient of friction were determined by nanohardness inde ntation and pin-on-disk wear testing of each sample. Ion beam analysis indicated a majority of the incident dose was retained. At a depth of 50 nm, the surface hardness increased from 18 +/- 1 GPa for unimplant ed chrome, to a maximum of 23 +/- 4 GPa for boron implanted chrome and 26 +/- 1 GPa for nitrogen implanted chrome. Pin-on-disk wear testing indicated reductions in the wear coefficient by factors of 1.3-7.4, de pending on the implantation treatment. It is shown that nitrogen impla ntation of chromium results in lower wear coefficients than boron impl antation. (C) 1997 Elsevier Science S.A.