Peculiarities of the Structural Phase Transformations during Annealing of Doped Titanium-Nitride Coatings

Abstract

Using the technique of electron-microscope dark-field analysis of the curvature–torsion of a crystal lattice in conjunction with microhardness measurements, a study has been performed of changes in the structural phase state and properties of titanium-nitride based coatings during annealings in vacuum to a temperature of 1573 K. It is shown that in coatings with submicron-size grains fragmented into nanosized subgrains, the magnitudes of local residual elastic stresses associated with elastoplastic curvature of the crystal lattice in regions of excess density of residual dislocations of one sign or with grain-boundary stress concentrators are of defining significance. It is established that in such coatings at high annealing temperatures (≥1373 K) grain coarsening and recovery of the intragrain defect structure develop non-uniformly while retaining high values of the density of the dislocations forming it and maintaining the low-angle boundaries at moderate lattice curvature. For annealings of nanocrystalline coatings, it is established that the intensity of precipitation of second-phase particles based on the doping elements has a defining influence on the hardness, characteristics of the structural state, and level of local stresses of titanium nitride nanocrystals.