ZrN coatings deposited by high power impulse magnetron sputtering and cathodic arc techniques.

Zirconium nitride (ZrN) coatings were deposited on 1 micron finish High Speed Steel (HSS) and 316L Stainless Steel (SS) test coupons. Cathodic Arc (CA) and HIPIMS (High Power Impulse Magnetron Sputtering) + UBM (Unbalanced Magnetron Sputtering) techniques were utilised to deposit coatings. CA plasmas are known to be rich in metal and gas ions of the depositing species as well as macro-particles (droplets) emitted from the arc sports. Combining HIPIMS technique with UBM in the same deposition process facilitated increased ion bombardment on the depositing species during coating growth maintaining high deposition rate. Prior to coating deposition, substrates were pretreated with Zr + rich plasma, for both arc deposited and HIPIMS deposited coatings, which led to a very high scratch adhesion value (LC2) of 100 N. Characterisation results revealed the overall thickness of the coatings in the range of 2.5 µm with hardness in the range of 30-40 GPa depending on the deposition technique. Cross-sectional Transmission Electron Microscopy (TEM), tribological experiments such as dry sliding wear tests and corrosion studies have been utilised to study the effects of ion bombardment on the structure and properties of these coatings. In all the cases HIPIMS assisted UBM deposited coating fared equal or better than the arc deposited coatings, the reasons being discussed in this paper. Thus H+U coatings provide a good alternative to arc deposited where smooth, dense coatings are required and macro droplets cannot be tolerated.