DEPOSITION AND MECHANICAL PROPERTY EVALUATION OF AMORPHOUS SILICON-CONTAINING DIAMOND-LIKE CARBON (SI-DLC) COATINGS ON STEEL

Amorphous silicon-containing diamond-like carbon (Si-DLC) coatings wer e deposited by Ar+ ion beam-assisted physical vapor deposition of tetr aphenyl-tetramethyl-trisiloxane (704 Dow Coming diffusion pump oil). T he steel substrates studied included AISI 4130, 17-7 PH, 440-C, and 43 40 (bare and nitride-precoated) specimens. DLC coating thicknesses ran ged from 1.8 to 4.31 mu. Deposition rates increased with increasing be am current density and varied with the steel substrate composition. Na noindentation measurements of the hardness and elastic modulus at two different depths yielded values of 9-10 GPa and 99-128 GPa, respective ly. Film cohesion and adhesion failure loads increased with increasing underlying Layer hardness, chromium content in the substrate, or the presence of a titanium nitride precoat. The friction coefficient of a diamond stylus against the coating surface decreased and wear resistan ce increased with nitride precoating.