Texture, microstructure and anti-wear characteristics in isostructural CrAlSiN/W₂N multilayer coatings

CrAlSiN/W₂N multilayer coatings are fabricated periodically by DC magnetron sputtering. Crystal phases and preferred orientations of thin films are characterized by an X-ray diffractometer. The microstructure of multilayer coatings is examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. Through high-resolution and dark-field TEM images, superlattice characteristics in multilayer coating are demonstrated. Owing to the densified architecture and interfacial strengthening with plenty of interfaces, CrAlSiN/W₂N multilayer coatings exhibit superior mechanical responses. With an appropriate bilayer period of 8 nm, the hardness boosts to a maximum around 41 GPa. In the ball-on-disk wear tests, it's found that all the multilayer coatings exhibit preferable anti-wear and friction characteristics, especially the one with a bilayer period of 20 nm. The worn surface of CrAlSiN monolayer is severely damaged with lots of cracks and delaminations, while that of multilayer coating is intact. Only thickness reduction in multilayer coating is observed in the cross-sectional view of wear scar. An anti-wear mechanism on the basis of microstructure evolution is proposed to elucidate the favorable durability in such a particular multilayer system.