Titanium-doped hydrogenated DLC coatings deposited by a novel OMCVD-PIIP technique

Abstract

Using a novel organometallic CVD-plasma immersion ion processing technique, titanium-doped hydrogenated diamond-like carbon (Ti-h:DLC) coatings were deposited from a metallorganic CVD precursor, tetrakis-dimethylamino titanium. A carrier gas of acetylene was used and the flow rate through the precursor reservoir was varied so the titanium concentration in the deposited coatings could be controlled. Deposited coatings had thickness in the range of 600–1000 nm as determined by surface profilometry. Titanium concentrations in the coatings ranged from 0.4 to approximately 11 at.%. Acetylene flow through the reservoir reached a peak efficiency of titanium throughput at 20 sccm, declining in efficiency as flow was increased to 40 sccm. Hardness values of these coatings ranged from approximately 8–17 GPa, as determined by nanoindentation, decreasing with increasing titanium content. Coefficient of friction values ranged from 0.23 to 0.18, and were lowest for coatings with high titanium content. The coefficient of friction followed the model for adhesive friction. Wear resistance was best for coatings with low titanium content as determined by pin-on-disk methods.