Low wear and low friction DLC coating with good adhesion to CoCrMo metal substrates

A challenge currently facing the orthopedics sector consists in the durability problems posed by joint prosthesis based on metal-on-metal contacts. While the diamond-like carbon (DLC)-based coating solves the shortcomings of wear and friction found in the uncoated metal parts, they are generally subject to adhesion failures that may prove to be catastrophic. Our coatings were deposited with a specific multilayered composition that changes from highly metallic at the metal interface, up to a DLC at the sliding contact region. These coatings show very good wear performance results when tested in a highly humid air atmosphere as well as when they are tested in water immersion or in bovine serum. The friction coefficients of our DLC-against-DLC tribological pair are found to be always less than 0.1, while wear rates are extremely low, under 2.5¿×¿10-8¿mm3/N¿m, and it produces highly polished surfaces. The compressive stresses of our coatings are always lower than 2.5¿GPa, and when combined with good interface adhesion to the CoCrMo metal substrates, make the coatings highly resistant to delamination even after prolonged test runs. Raman analyses do not reveal any detectable changes even after very long test runs, indicating that no tribochemical reactions occur on the DLC coating