The Structural and Mechanical Properties of CrAlTiN-Si Nanostructured Coatings Deposited by the Means of High-Power Impulse Magnetron Sputtering

CrAlTiN-Si coatings have demonstrated their ability to prolong the operational life and improve the performance of cutting tools, primarily attributable to their exceptional mechanical, thermal, and tribological properties. Consequently, this investigation focused on the deposition of CrAlTiN-Si coatings utilizing the high-power impulse magnetron sputtering (HiPIMS) technique. The chemical composition, morphology, and microstructure of these coatings, as well as their mechanical and tribological properties, were investigated. The obtained results revealed that the incorporation of silicon into the CrAlTiN matrix significantly influenced the chemical composition, microstructure, and mechanical properties of the coatings. Specifically, silicon contents ranging from 0 to 1.0 at.% led to the formation of a face-centered cubic (fcc) solid solution within the coatings, resulting in a reduction in the lattice parameter from 0.412 nm to 0.409 nm. However, when the silicon content reached 1.9 at.%, a nanocomposite phase comprising an fcc solid solution of CrAlTiSiN and an amorphous phase of SiNx was observed, along with an increase in the lattice parameter from 0.409 nm to 0.413 nm. An XPS analysis confirmed the presence of oxides in all the coatings, but only the sample with a silicon content of 1.9 at.% showed the presence of Si-N bonds. Furthermore, all the coatings exhibited a distinctive cauliflower-type morphology. The nano-hardness testing demonstrated that the incorporation of silicon resulted in coatings with high nano-hardness values, from 20.0 GPa for the sample without silicon to 22.2 GPa when the silicon content was 1.9 at.%. Moreover, as the Si content increased, the presence of silicon contributed to enhancements in the toughness and fracture resistance of the coating.