Combined Oxygen - Nitrogen Ion Implants Into Ti6A14V
- PDF / 972,498 Bytes
- 6 Pages / 420.48 x 639 pts Page_size
- 110 Downloads / 237 Views
COMBINED OXYGEN - NITROGEN ION IMPLANTS INTO Ti6Al4V ANTON GREENWALD, JAMES DALY, JOHN MEROTH, RICHARD OLIVER, and CLIVE CLAYTON* Spire Corporation, Patriots Park, Bedford, MA 01730 *State University of New York at Stony Brook, NY
PIRAN SIOSHANSI,
ABSTRACT The alloy preferred for medical protheses, Ti6Al4V, was ion implanted with oxygen and nitrogen alone and in combination at varying energies, 25 to 120 keV, and varying dose levels, 1017 to 1018 ions/cm2 . Measurements were made of microhardness, corrosion resistance, chemical bonding of implanted species, and (with UHMW polyethylene) pin-on-disk wear and friction. The addition of oxygen to nitrogen implants now used in production was found to have little effect on wear or any other parameter. INTRODUCTInN The objective of this research is to utilize ion implantation to improve the tribomechanical properties of Ti6Al4V, an alloy being used for orthopaedic prostheses. Previous experimentation has shown that ion implantation with nitrogen has substantially improved the wear characteristics of this alloy [1]. It has been reported that oxygen, present as a contaminant in the vacuum system, was incorporated into the surface during nitrogen implantation, and that this oxygen had the effect of reducing friction [2]. It has also been suggested that the nitrogen implants reduced wear by actually stabilizing oxide phases of the alloys which formed on the surface during normal use [3]. Ion implantation of oxygen alone has had a deleterious effect on the wear of this alloy [4]. Experiments reported here were designed to optimize implant conditions and investigate possible benefits of intentionally implanting oxygen along with nitrogen. RESULTS Sample Preparation Samples for testing hardness, friction and corrosion were disks approximately 1 cm diameter by 5 mm thick, cut from an alloy rod 6.1% Al, 4.2% V, 0.17% Fe, less than 0.1% other elements with the balance being Ti. The disks were polished to a mirror finish using 0.05 micron powdered alumina slurry in the last step. All samples were thoroughly cleaned with a final alcohol rinse before implantation. Disks were held on a water cooled plate during ion implantation. Hemispherical pins for pin-on-disk wear measurements were similarly prepared from 0.63 cm diameter stock. The pins were not actively cooled during implantation; instead, the ion beam was defocussed so as to cover a large area and the maximum temperature of the pins during the procedure was kept under 100°C. Hardness and Friction A large factorial matrix experiment was tion of four variables (ion energy and dose nitrogen) [5]. Implantation cond'itions are different conditions were chosen, with four Mat. Res. Soc. Symp. Proc. Vol. 128. C1989 Materials Research Society
devised for testing the correlafor each of two ions, oxygen and given in Table I. A total of 16 sample conditions duplicated to
464
TABLE I. Sample Number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 lg 20 21,22,23,24
FACTORIAL MATRIX SAMPLE CONDITIONS.
0+ Dose 2 (Ions/cm ) 0.0 0.0 0.0 0.0 3.
Data Loading...
