Mechanical and tribological properties of multilayered PVD TiN/CrN

By combining thin layers of PVD titanium nitride (TiN) with thin layers (preferably less than 10 nm) of another nitride, e.g., niobium nitride (NbN) or aluminum nitride (AlN), into a lamellae structure, a coating with superior properties to the homogenous coatings made from the constituents can be obtained. For example a very high hardness in combination with a high toughness, and thereby a high resistance to abrasive wear, have been reported for such multilayered coatings. In this work a new multilayered PVD coating, TiN/CrN, deposited on cemented carbide have been evaluated with respect to the hardness, residual stress, coating cohesion/adhesion and the abrasive wear resistance. Especially the influence of the chemical modulation period (thickness of one lamella of TiN together with one lamella of CrN) and thickness ratio (TiN/CrN ratio) of the individual layers on the above properties have been investigated. In addition, the effect of substrate bias, magnetron power and nitrogen flow during deposition have been studied. As reference material, homogenous TiN and CrN have been used. The TiN/CrN coatings were deposited using a hybrid process which combines reactive electron beam evaporation of TiN and reactive de magnetron sputtering of CrN. In general, multilayered TiN/CrN was found to have superior properties to both homogenous TiN and CrN. It could also be seen that the lamella thickness in the multilayered coating and especially the lamella thickness of the CrN should be kept thin in order to obtain as good mechanical and tribological properties of the coating as possible. (C) 1999 Elsevier Science S.A. All rights reserved.