Microstructures, mechanical properties, and tribological behaviors of Cr–Al–N, Cr–Si–N, and Cr–Al–Si–N coatings by a hybrid coating system

Cr–Al–N, Cr–Si–N, Cr–Al–Si–N coatings were successfully deposited on WC–Co substrates by a hybrid coating system combining an arc ion plating technique using Cr target, and a magnetron sputtering method using Al and Si targets under N2/Ar atmosphere. XRD, HRTEM, and XPS analyses revealed that the synthesized Cr–Al–N coatings consisted of solid-solution (Cr,Al)N crystallites, and the Cr–Si–N and Cr–Al–Si–N coatings with Si content of ∼ 9 at.% were fine composites consisting of (Cr,Si)N and (Cr,Al,Si)N crystallites, respectively, embedded in an amorphous Si3N4/SiO2 matrix. The hardness values of the Cr–Si–N (∼ 35 GPa) and the Cr–Al–Si–N (∼ 55 GPa) coatings were significantly increased compared with those of CrN (∼ 23 GPa) and Cr–Al–N (∼ 25 GPa) coatings. Besides, the average friction coefficients of the Cr–Si–N (∼ 0.30) and the Cr–Al–Si–N (∼ 0.57) coatings with Si content of about 9 at.% were largely decreased compared with those of CrN (∼ 0.50) and Cr–Al–N (∼ 0.84) coatings. A comparative study on microstructural characteristics among Cr–Al–N, Cr–Si–N, and Cr–Al–Si–N coatings is reported in this paper.