Low friction CrN/TiN multilayer coatings prepared by a hybrid high power impulse magnetron sputtering/DC magnetron sputtering deposition technique

High power impulse magnetron sputtering (HIPIMS) has gained increasing scientific and industrial attention as it allows high plasma densities without the drawback of droplet formation. Recently, we showed that by a combination of HIPIMS with dc magnetron sputtering the properties of the coatings are comparable to those prepared solely with HIPIMS, but with the advantage of increased deposition rate. Here, we show that for CrNHIPIMS/TiNDCMS multilayered coatings the friction coefficient mu decreases from 0.7 to 0.35 (with an almost constant hardness H around 25 GPa, and modulus of indentation around 375 GPa) when decreasing the bilayer period lambda from 7.8 to 6.4 nm, while keeping the CrNHIPIMS layer thickness constant at 3.2 nm. A further reduction of the friction coefficient at room temperature dry-sliding testing to similar to 0.25 or 0.05 is obtained when an additional HIPIMS cathode equipped with a Cr or Ti target material, respectively, is added to the process. Contact angle measurements of distilled water drops on as deposited film surfaces were carried out to investigate their wettability. The measurements show, that with increasing contact angle from 70 degrees to 90 degrees, for the individual coatings prepared, also their friction coefficient increases from similar to 0.05 to similar to 0.8. The depositions of all coatings were achieved with two- and threefold substrate rotation, which meet the industrial requirements of uniform deposition on complex shaped specimens. (C) 2010 Elsevier B.V. All rights reserved.