Role of nonlocal thermoelastic peaks in the stress and texture evolution of TiN coatings formed by plasma based ion implantation and deposition
Résumé
A thermodynamic approach based on the concept of nonlocal thermoelastic peaks (NTP), which are generated by implanted ions, is used to explain the structure formation and stress state in TiN coatings synthesized by plasma immersion ion implantation and deposition by filtered vacuum-arc plasma. The radius, the depth of the accumulation and the temperature in the NTP are determined, depending on the energy that the ions acquire under the action of the accelerating potential. The structure and compressive stress level in the coatings are considered together, as a result of the competition between two different atomistic processes in the NTP: radiation-induced defects formation and their removal due to thermal migration. It is supposed that the result of competition provides a minimum of free energy of the synthesized coating. A structure-stress state diagram of nitride coatings deposited under conditions of ion implantation is proposed. Relaxation processes in coatings associated with decrease of stress and change of texture from [111] to [110] or [100] are activated when the peaks temperature exceeds 1/3 of the melting point Tm.