Toughness enhancement in zirconium-tungsten-nitride nanocrystalline hard coatings

Abstract

An approach is presented to increase the toughness (KIC) while retaining high hardness (H) of Zr-W-N nanocrystalline coatings using energetic ions bombardment. Tuning KIC and H values was made possible by a careful control over the substrate bias, i.e., the kinetic energy (Uk∼9-99 J/cm3) of the bombarding ions, while keeping the deposition temperature relatively low (200 oC). Structural and mechanical characterization revealed a maximum wear resistance (H/Er∼0.23) and fracture toughness (KIC∼2.25 MPa m) of ZrWN coatings at Uk∼72 J/cm3. A direct Uk-microstructure-KIC-H relationship suggests that tailoring mechanical properties for a given application is possible by tuning Uk and, hence, ZrWN-coatings' microstructure.