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Ion implanation of titanium workpieces without surface discoloration
| Details |
Inventors: Sioshansi, Piran;
Assignee: Spire Corporation (Bedford, MA)
Primary Examiner: Rutledge; L. Dewayne
Assistant Examiner: Kastler; S.
Attorney, Agent or Firm: Morse, Altman & Dacey
A process for preventing surface discoloration in orthopedic implants made of titanium and its alloys is disclosed. Such surface discoloration is apt to occur when the orthopedic implants are ion implanted to improve their wear characteristics. The process essentially includes exposing all fixtures and shields, made of pure titanium, located in an implant chamber, to an ion beam, creating a vacuum within the chamber not exceeding about 5.times.10.sup.-5 torr, introducing an orthopedic implant within the chamber to be directly exposed to the beam, and reducing the ion beam current power density so as not to exceed about 1.0 watt/cm.sup.2. Exposing the fixtures and shields to the ion beam first serves to remove surface contamination therefrom, followed by forming a surface layer thereon. This surface layer effectively lowers the sputtering coefficient of the fixtures and shields, and thus reduces the amount of material sputtered from areas exposed to the ion beam to unexposed areas. Preferably, the vacuum is created by using an oil-free vacuum pump. |
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DETAILED DESCRIPTION It is a principal object of the present invention to overcome the above disadvantages by providing a process for preventing the surface discoloration of orthopaedic surgical implants made of titanium and its alloys and occurring during their ion implantation.
More specifically, it is an object of the present invention to provide a process for the prevention of surface discoloration in workpieces, such as used for orthopaedic surgical implants and made from titanium and its alloys, during their ion implantation designed to improve their wear resistance, the process comprising exposing all of the fixtures and shields made from pure titanium and mounted within an ion implanter chamber to an ion beam so as to condition these fixtures and shields by removing any surface contamination therefrom and by forming a surface layer thereon characterized by possessing a sputtering coefficient lower than that of pure titanium, creating a vacuum in the ion implantation chamber which does not exceed 5.
times.
10.
sup.
-5 and preferably is about 1.
times.
10.
sup.
-6 torr and preferably employing an oil-free vacuum pump to avoid surface discoloration, introducing a workpiece formed of titanium and its alloys into the ion implantation chamber and being secured therein by the conditioned pure titanium fixtures in such a way as to be arranged in a direct line of the ion beam, the beam having an ion beam power density on the surface of the workpiece not exceeding about 1.
0 watt/cm.
sup.
2 and preferably being about 0.
5 watt/cm.
sup.
2, and exposing the workpiece to the ion beam to ion implant the surface thereof.
Preferably, the ion beam incorporates one of a group of elemental species including nitrogen, carbon, chromium, zirconium, oxygen, boron, tin, iron, tantalum, molybdenum, neon, argon krypton and xenon.
As a consequence of the process, the surfaces of the workpieces formed of titanium and its alloys will remain of the same natural color and hue after their ion implantation designed to improve their wear performance as they were prior to their ion implantation, i
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Semiconductor manufacture 
