Multicomponent hard and superhard submicro- and nanocomposite coatings on the basis of titanium and iron nitrides

Electron microscopy, X-ray structure analysis as well as micro- and nanohardness measurements are used to study the relation between the fine structure and variation of strength properties of nanostructured and nanocomposite Ti-Si-B-N and Ti-Al-Si-N coatings with high oxygen and carbon content. For all studied alloys and deposition modes we have revealed the crystalline phase Ti_1-xSi_xN with the lattice parameters a = (0.416-0.420) ± 0.001 nm. In the conditions of low-temperature (T = 200 °C) coating deposition a two-level grain structure with the fragmentation of 0.1-0.3 μm grains into 15-20 nm subgrains and with {200} texture is formed. The generality of the conclusion about the two-level grain structure formation at a columnar growth of the coating is substantiated for (Fe, Cr, Ni)₄N coatings. With silicon content growth texture-free coatings with lattice grain size less than 15 nm and high fraction of the amorphous phase are formed. At coating deposition temperatures 400-450 °C one can see a nanocomposite structure with the grain size d = 10-15 nm and no texture. At optimal compositions and synthesis conditions the hardness values exceed 40-50 GPa. We suppose that it is possible to achieve superhardness for multiphase grain boundary interlayers more than 1 nm thick.