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 μm and the period thickness is 1–160 nm. It was found that under a critical thickness ∼2 nm for the AlN 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, AlN 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 AlN phase and the other properties associated with the formation of the ordered microstructure.