CVD deposition of nanocrystalline diamond coatings on implant alloy materials with CrN/Al interlayer

Integration of smooth nanocrystalline diamond coatings on biomedical implant substrates (CoCr, SS316) for enhanced biomedical performances has great application potentials due to their extraordinary wear/corrosion resistance and biocompatibility. However, chemical vapor deposition (CVD) of adherent diamond coatings on such substrates encounters a major technical barrier of weak interface bonding strength. In this study, single CrN interlayer of different thickness and duplex CrN/Al interlayer have been prepared on CoCr alloy and SS316 steel substrates to improve the adhesion of diamond coatings. The diamond coating produced with a single CrN interlayer up to 1 μm thick still shows insufficient adhesion ability to the substrates. A combination of CrN and Al, with a total thickness of 0.45 μm, significantly enhances the diamond coating/substrate bonding strength. The fundamental mechanism of enhanced interfacial adhesion is discussed in terms of the individual role the two kinds of interlayer materials play.