Synthesis and characterization of Cr–B–N coatings deposited by reactive arc evaporation

Nanocomposite Cr–B–N coatings were deposited from CrB_0.2 compound targets by reactive arc evaporation using an Ar/N₂ discharge at 500 °C and −20 V substrate bias. Elastic recoil detection (ERDA), x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and selected-area electron diffraction (SAED) were used to study the effect of the N₂ partial pressure on composition and microstructure of the coatings. Cross-sectional scanning electron microscopy (SEM) showed that the coating morphology changes from a glassy to a columnar structure with increasing N₂ partial pressure, which coincides with the transition from an amorphous to a crystalline growth mode. The saturation of N content in the coating confirms the formation of a thermodynamically stable CrN–BN dual-phase structure at higher N₂ fractions, exhibiting a maximum in hardness of approximately 29 GPa.