THE EFFECT OF BIOLOGICAL-FLUIDS ON THE ADHESION OF DIAMOND-LIKE CARBON-FILMS TO METALLIC SUBSTRATES

Diamond-like carbon (DLC) films deposited by standard r.f. glow discha rge CVD were exposed to various fluids (distilled water, phosphate-buf fered saline (PBS) solution and 40% serum in PBS) to study the effect of this exposure on the stability of DLC coatings on metallic substrat es. A substrate plastic straining technique was used to study the stre ngth and adhesion of the coatings before and after exposure to various fluids. Distilled water had no apparent effect, whereas PBS caused lo calized debonding and cracking of the film. The serum-PBS solution had an intermediate effect. X-Ray photoelectron spectroscopy (XPS) measur ements indicated that PBS tends to penetrate through surface perforati ons and attack the thin transition layer of graded Si/C composition be tween the Si-rich layer on the substrate and the DLC coating. An incre ase in exposure temperature increased the population of defects in sam ples exposed to PBS. Coatings on Ti were found to be more resistant to damage.