Composition and Thickness Effect of TiAlN-Type Nanocoatings on the Strength of Their Bond with Iron: Quantum Chemical Analysis

Atomic structures arising during the vacuum deposition of TiAlN nanocoatings on the iron surface are studied using quantum chemistry methods. The effects that appear during the deposition of the first atomic layers of such coatings are considered. Calculations of the bond strength of such coatings with the surface are carried out. Within the framework of the model used in this study, it is shown that the most durable is the coating, the lower layer of which consists of Ti atoms, located directly on the iron surface. The upper layers consist of a mixture of Ti, Al, and N atoms. The bond strength of such a coating with iron can increase by 13% compared to its bottom value. When modeling the interaction of the coating with the substrate, it is has been established that the strength of the bond between the components is almost independent of the substrate thickness, if the substrate consists of three or more iron atomic layers. This fact testifies to the short-range nature of the interatomic forces at the coating–substrate interface, which greatly simplifies the theoretical analysis of the strength properties of such systems. The paper shows that when calculating the atomic configurations appearing on the iron surface during vacuum deposition, it is necessary to look for configurations with a minimum energy. It is these configurations that are most likely to form on the substrate surface. Traditional methods of studying atomic structures based on the principle of the minimum system enthalpy are not applicable in this case. The results of this study are compared with known experimental data related to similar objects.