Effect of Si addition on the microstructure, mechanical properties and tribological properties of Zr-Si-N nanocomposite coatings deposited by a hybrid coating system

Zr-Si-N coatings with various Si contents were synthesized by a hybrid coating system combining arc ion plating and d.c. magnetron sputtering techniques. The influence of the Si content on the microstructure, mechanical properties and tribological properties of the Zr-Si-N coatings was investigated. The results showed that as the Si content increased from 0 to 5.8 at.%, the coatings transformed from a columnar ZrN to nanocomposite structure with a nano-sized ZrN crystallites embedded in amorphous Si3N4 matrix and further increases of Si content lead to amorphous-like coatings. The maximum hardness (H) of 33 GPa, Young's modulus (E) of 265 GPa, and H/E⁎ value of 0.12 were obtained at Si content of 5.8 at.% in the Zr-Si-N coatings, respectively. The coating with the lowest friction coefficient and the best wear resistance was also obtained at Si content of 5.8 at.%, which was mainly contributed to high value of H/E⁎ and formation of SiO2 or Si(OH)4 self-lubricating layer due to the interface tribo-chemical reaction.