Fabrication of CrAlN nanocomposite films with high hardness and excellent anti-wear performance for gear application

CrAlN nanocomposite films with various Al contents were prepared by a reactive magnetron sputtering technique using Cr and Al targets in the reactive gas mixture. The micro-structure, mechanical properties and tribological behaviors of traditional CrN and newly-fabricated CrAlN nanocomposite films were compared. XRD results showed that single-phase fcc (face-centered cubic) CrAlN films formed a solid solution whereby Cr atoms were substituted by Al atoms. High resolution TEM results demonstrate that the CrAlN film possesses a unique amorphous/crystalline nanocomposite micro-structure with ∼ 5 nm crystalline uniformly embedded into an amorphous matrix. In addition, CrAlN nanocomposite films exhibited relatively smaller grain size and denser structure when compared with CrN films. All the CrAlN nanocomposite films with the highest hardness being approximately 33.4 GPa exhibited much higher hardness and better wear resistance than traditional CrN films The excellent anti-wear performance of CrAlN nanocomposite films can be attributed to an amorphous/crystalline nanocomposite micro-structure and their high hardness. CrAlN nanocomposite films are considered as potential protective surfaces for such kinds of moving parts as gears, cutting tools and shafts used in engine and other mechanical mechanisms.