Influence of Si content on the structure and internal stress of the nanocomposite TiSiN coatings deposited by large area filtered arc deposition

Abstract

TiSiN coatings were deposited by using a large area filtered arc deposition technique from TiSi targets with different Si content. The influence of the Si content in the targets on the surface morphology, composition, bonding structure, crystalline structure and internal stress of the TiSiN coatings were systematically studied by using scanning electron microscopy, x-ray photoelectron spectroscopy, x-ray diffraction and the substrate curvature method, respectively. It was found that by increasing Si content in the TiSi targets to 20 at%, the Si content in the coatings increases linearly to 7.7 at%. Both XRD and XPS results indicate that all the TiSiN coatings consist of a nanosized TiN phase and an amorphous Si3N4 phase except for the coatings with Si content of above 4.5 at%, in which 5% of amorphous TiSi2 phase exists. With increasing Si content in the coating, the coatings change orientation from the (1 1 1) to the (2 2 0) preferred orientation. The TiN grain size decreases linearly to 5.4 nm with an increase in Si content up to 4.5 at%, and then increases slightly with a higher Si content in the coatings. The substrate curvature method shows that the increase in the Si content from 0 to 4.5 at% results in a rapid increase in the internal stress in the coating from 2.2 to 3.9 GPa, but a further increase in the Si content leads to a slight decrease in the internal stress in the coating. The decrease in the grain size with increasing Si content contributes to the increase in the internal stress in the TiSiN coatings.