Influence of Si contents on tribological characteristics of CrAlSiN nanocomposite coatings

• The friction coefficient of CrAlSiN films decrease with increasing Si content.
• The wear rate of CrAlSiN films is dependent on resistance to plastic deformation.
• Si-induced amorphization is attributed to the absence of penetrated cracks.

The CrAlSiN coatings with Si contents from 0 at.% to 13.0 at.% were deposited on AISI 304 stainless steels and tungsten carbide by RF magnetron sputtering. In the ball-on-disc wear tests, the improved friction coefficient of (Cr0.5Al0.5)1 −xSixN coatings with increasing Si content was revealed. The hardness (H) and the reduced elastic modulus (E⁎) of (Cr0.5Al0.5)1 −xSixN coatings were acquired by a nanoindentation. The H3/E⁎2 ratio of (Cr0.5Al0.5)1 −xSixN coatings was found be proportional to the abrasion resistance of coatings, and therefore the (Cr0.5Al0.5)1 −xSixN coating with maximum H3/E⁎2 ratio as high as 0.475 by adding 9.0 at.% Si exhibited superior resistance to plastic deformation and wear. In addition, it was revealed that the columnar grains of the CrAlN coatings were switched to refined and equi-axial ones after Si addition. From the observation of crack propagation, it was evidenced that the equi-axial grains with sophisticated boundary of (Cr0.5Al0.5)1 −xSixN coating prevents the direct penetration of the cracks. On the basis of these improved tribological behaviors, the superior durability of (Cr0.5Al0.5)1 −xSixN coating is thus demonstrated.