Influence of the N2 partial pressure on the mechanical properties and tribological behavior of zirconium nitride deposited by reactive magnetron sputtering

Zirconium nitride was deposited by reactive unbalanced magnetron sputtering at different N-2 partial pressures, on an AISI 316L stainless steel substrate. The mechanical properties of the coatings were evaluated by means of nanoindentation tests employing a Berkovich indenter and loads which varied between 120-9000 mu N. The sliding wear behavior of the substrate-coating systems was studied under a normal load of 2 N using a ball-on-disc tribometer, with an AISI 52 100 ball (6 mm diameter) as counterpart. It has been found that N2 partial pressure has a significant effect both on the hardness and corresponding Young's modulus of the coatings. As the N2 partial pressure increases from 1 x 10(-4) Torr to 10 x 10(-4) Torr, the hardness and Young's modulus of the coatings decrease from 26 to 20 GPa and 360 to 280 GPa, respectively. The nanoindentation tests revealed the presence of a third oxide layer (10 rim thick, approximately) on the surface of the coating. Scanning electron microscopy (SEM) analysis performed on the worn triboelements indicated that both abrasive and adhesive wear mechanisms could take place in addition to the substrate plastic deformation. The deposition conditions and coating mechanical integrity determine the predominant wear mechanism. (C) 2009 Elsevier B.V. All rights reserved.