Peculiarities of Structural Phase and Elastic Stress States of Superhard TiN-Based Nanocomposite Coatings

A new concept of designing nanocomposite coatings is proposed. The concept consists in microstructural self-organization through simultaneous nucleation of islands of different mutually insoluble or slightly soluble phases at the stage of coating formation. Physical principles on which to select compositions of the coatings were developed and were experimentally verified on multicomponent nanocomposite coatings. With a Sprut magnetron arc plasma complex, superhard (H-mu > 40 GPa) multicomponent nanocomposite coatings of the system Ti-Al-Si-Cr-Ni-Cu-O-C-N were obtained. The peculiarities of structural phase and elastic stress states of the multicomponent coatings before and after annealing at a temperature of up to 1000 degrees C were studied by transmission electron microscopy, X-ray diffraction analysis, microhardness measurements and scratch tests. The study reveals a wide range of lattice bending-torsion (up to 200 degrees mu m(-1)) of nanosized (less than 30 nm) coherent scattering regions in the two-level coating structure and of individual (up to 15 nm) TiN nanocrystals. Annealing of the coatings causes the two-level grain structure to relax with the formation of TiN-based nanocrystals of size less than 30-40 nm and with a decrease in lattice bending-torsion down to 40 degrees-50 degrees mu m(-1). Comparative analysis of acoustic emission signals and tracks of the multicomponent and TiN coatings in scratch tests points to an increase in fracture ductility in the multicomponent coatings.