Development of a Plasma-Based Process for the Deposition of Adherent Diamond-Like Carbon Coating on Titanium Implants

Titanium and its alloys are considered the gold standard for bone contact implants due to their suitable mechanical properties and biological performances. However, their long-term performance remains impaired, mainly due to insufficient integration with surrounding tissues and infections. To overcome these problems, several strategies, particularly coatings, are explored. However, certain drawbacks remain such as lack of adhesion or low mechanical resistance. Among these coatings, diamond-like carbon (DLC) has emerged as a promising material due to its superior mechanical and tribological properties, chemical inertness and stability. In addition, the microstructure of DLC allows the incorporation of other species such as antibacterial agents (Ag, ZnO, etc.), leading to multifunctional protective coating. However, due to the high intrinsic stresses of DLC compared to the native oxide layer, the adhesion of DLC to metallic surfaces remains rather low. Therefore, in order to overcome adhesion issues, this work investigates the impact of different pretreatments, namely etching, carburization or both, on the adhesion of DLC deposited by plasma-assisted chemical vapor deposition, on titanium substrates. The results showed that carburizing 10 min was the most promising pretreatment for improving the DLC adhesion on Ti surfaces. Furthermore, the DLC coating appeared stable even after 7 days of aging in pseudo-physiological conditions, making the process promising for improving Ti implants.