DLC based coatings prepared by reactive d.c. magnetron sputtering

Abstract Metal containing diamond-like carbon (a-C:H:Me/Me-DLC) coatings commonly will be prepared by reactive magnetron sputter deposition using targets from transition metals or transition metal carbides and acetylene as reactive gas. It is well known that Me-DLC coatings have very similar friction properties like hard hydrogenated amorphous carbon (a-C:H/DLC) coatings. However, even optimized Me-DLC nearly without exceptions exhibits clearly lower wear resistances and lower hardness values than metal free DLC. To get more insight in the effects of metal incorporation, both W-DLC using tungsten targets and metal free coatings using graphite targets were prepared. For the latter, we introduce the name C-DLC. The deposition experiments were carried out in an industrial scale d.c. magnetron sputter machine. To have a reference material metal free a-C:H was deposited by radio frequency and by mid frequency (m.f.—some 10–100 kHz) glow discharge techniques operating with acetylene. Transmission electron microscopy (TEM), secondary ion mass spectroscopy (SIMS) and Raman spectroscopy investigations as well as hardness measurements and abrasive wear tests revealed that C-DLC coatings have nearly identical composition and structure and also rather similar mechanical and tribological properties like a-C:H deposited by r.f. or m.f. processes. However, for all these features essential differences between C-DLC and W-DLC coatings were found.