The subject of the invention is a medical implant, in particular an element of a mechanical heart valve, made from polyetheretherketone, characterised in that it has a gradient surface layer (2), comprising the following coatings from the base of the implant: - an amorphous hydrogenated nitrogen doped carbon coating ( 3) - a-C:N:H - an amorphous or amorphous-nanocrystalline hydrogenated nitrogen and silicon doped carbon coating (4) - a-C:N:H(Si) or C:N:H(Si) - an amorphous or nanocrystalline or amorphous-nanocrystalline silicon carbonitride coating (5) - a-SiCN(H) or SiCN(H) wherein the surface layer (2) comprising the coatings (3, 4, 5) is formed through argon Ar + ion etching in an atmosphere containing precursors of carbon, nitrogen, silicon and argon as carrier gas in the temperature within the range between 22°C and 100°C, at pressure in a working chamber within the range between 0.1 and 2 milibar with the use of chemical vapour deposition from gas phase with the use of chemical reactions with the use of current-generated plasma or microwave-generated plasma.
