Improved adhesion of diamondlike coatings using shallow carbon implantation

A surface layer of metal carbides provides an excellent interface to achieve a highly adherent diamondlike carbon (DLC) coating. A plasma immersion ion implantation (PIII)-based procedure is described, which delivers a high retained dose of implanted carbon at the surface of aluminum alloys. A shallow implantation profile, followed by argon sputter cleaning and continued until a saturated carbon matrix is brought to the surface, provides an excellent interface for subsequent growth of DLC. At a carbon retained dose above 1018 atoms/cm2 the DLC adhesion exceeds the coating's cohesion strength. Regardless of the silicon content in the aluminum, the coating produced by this method required tensile strengths typically exceeding 140 MPa to separate an epoxy-coated stud from the coating in a standard pull test. Improved DLC adhesion was also observed on chromium and titanium. The reported tensile strength is believed to substantially exceed performance of DLC coatings produced by any other method.