Microstructure and mechanical properties of nanostructured Ti-Al-Si-N coatings deposited by magnetron sputtering

Reduction of wear and corrosion, along with increasing thermal stability of tools and mechanical components presents industrial challenges which demand continuous development of new coating materials and coating design concepts. Recently, the main attention has been placed on research and application of multilayer and nanocomposite coatings. In this study, TiAlN and TiSiN layers were alternatively deposited to produce a nanolayered nanocomposite TiAlSiN coating. Single-layer TiAlN and TiSiN coatings were deposited along with the nanolayered coating for better understanding of its properties. All coatings were prepared by sputtering in an industrial unit equipped with four unbalanced magnetron sources (two TiAl and two TiSi). Coating microstructure was analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). Chemical and phase compositions were determined by X-ray photoelectron spectroscopy (XPS). Mechanical properties were measured by nanoindentation technique. According to XRD and XPS measurements, nanolayered TiAlSiN coating consists of crystalline fcc-TiN like and amorphous Si3N4 phases. TEM analysis revealed that TiSiN layers block the growth of TiAlN crystallites which are equiaxed and size around 5 nm. As a result, TiAlSiN coating exhibits high hardness (H = 39 GPa) which is attributed to limited dislocation activity in small crystals and suppression of grain boundary sliding.