The improved joint prosthesis includes a metal-based substrate forming an articulatory surface for the joint prosthesis, wherein the metal-based substrate is coated with a ceramic or ceramic-based surface coating of a thin film doped silicon nitride (Si3N4) layer thereon, as disclosed in U.S. Pat. No. 6,881,229. The ceramic coating provides improvements in ultra-low wear over an extended service life, with dramatically reduced risk of brittle fracture when articulated or moved against articulation surfaces such as an acetabular cup in a hip prosthesis. In one preferred formation process, the ceramic coating is applied to the metal substrate by vapor deposition to mirror the surface finish of the substrate, and then polished to a smoother surface finish.
