Preparation and characterization of AlN/ZrN and AlN/TiN nanolaminate coatings

The processing, microstructure and properties of AlN/ZrN and AlN/TiN nanolaminate coatings were studied. Advanced ion-assisted, high-rate, reactive and pulsed-d.c. magnetron sputtering technique was used to deposit the nitride coatings onto Si, glass slide and stainless steel substrates. The thickness of the nanolaminate coating is approximately 2 mum and the period thickness is 1-160 nm. It was found that under a critical thickness similar to 2 nm for the AIN layer the AlN/TiN nanolaminates exhibit a highly textured [111] oriented superlattice structure and an enhancement in film hardness. X-Ray diffraction and TEM studies indicate that in the highly [111] textured multilayered films, AW has transformed into a nano-stabilized cubic NaCl-form from its normal hexagonal phase. However, in the case of AlN/ZrN prepared under the growth conditions comparable to those for AlN/TiN, no highly textured structure, no cubic AlN phase and no hardness enhancement was observed. The results indicate that the lattice structure and lattice match in AlN-containing nanolaminates are important for formation of the metastable cubic AW phase and the other properties associated with the formation of the ordered microstructure. (C) 2000 Elsevier Science B.V. All rights reserved.