Stress and adhesion in DLC coatings on 316L stainless steel deposited by a neutral beam source

Diamond-like carbon (DLC) films have been deposited on medical implant grade 316L stainless steel substrates using a saddle field source neutral beam deposition system. The deposition characteristics have been determined as a function of system parameters and it has been shown that the deposition rate is largely independent of chamber pressure. The film structure has been investigated using Raman spectroscopy and from the peak positions and intensities the sp3 content has been estimated to be ∼20% maximum. No significant change with film pressure has been observed but higher anode currents may lead to higher sp3 content. The adhesion strength has been found to be inversely proportional to the residual stress and to increase at lower deposition pressures. At a source anode current of 0.6 A the adhesion is a monotonic function of pressure in the range examined whereas with 1.0 A source current the behaviour is more complex.