Features of the modification of microstructure and properties for copper-doped titanium nitride coatings

Abstract

Features of a defective microstructure and the mechanical properties of titanium nitride coatings having different copper content are investigated by means of transmission electron microscopy, X-ray structural analysis, microhardness measurement, and scratch tests. It is shown that, under a relatively low deposition temperature and ion-induced surface activation during the growth of a TiN-Cu coating, a highly defective single-phase crystalline state of titanium nitride is formed at a copper concentration of up to 12 at %. The noted state is characterized by a scale hierarchy of the lattice fragmentation from sizes of ∼10–15 to 100 nm, high bending-torsion of the crystal lattice (tens of degrees per micron), and a level of local internal stresses from ∼E/40 to ∼E/120 (E is the modulus of elasticity). The revealed high gradients, including those of a dipole character, for the bending-torsion on characteristic scales up to some tens of nanometers can be described within the framework of a model for the continuous distribution of dislocation-disclination ensembles. The effect of the copper content on an increase in the degree of dispersion of the subgrained structure, a decrease in the local bending-torsion of the crystal lattice within subgrains, the level of local internal stresses, and variation of the hardness and strength in scratch tests is revealed.