Theoretical calculation of adhesion performance and mechanical properties of CrN/α-Fe interface

The lattice mismatches between CrN and alpha-Fe low-index crystallographic plane were calculated by Bramfit two-dimensional lattice mismatch theory. The surface properties of alpha-Fe(100) and CrN(100), and the interfacial relationship of CrN/alpha-Fe were calculated by first-principles method. The tensile, shear and nano-indentation behaviors between CrN/alpha-Fe interface were analyzed by molecular dynamics (MD) simulations. The results show that the mismatch between CrN(100)/alpha-Fe(100) is the smallest, which is 3.78% < 6%. It indicates that the lattice matching is very effective. According to different stacking methods, CrN(100)/alpha-Fe(100) interfaces can be divided into two interfaces, namely Fe-N and Fe-Cr ones. The adhesion work of Fe-Cr interface is the largest (1.065 eV/angstrom(2)) and its interfacial energy is the smallest (1.051 eV/angstrom(2)), which indicates that the Fe-Cr interface is the most stable. From the density of states and charge density analysis, it is found that there are covalent bonds, ionic bonds and metal bonds in the Fe-Cr and Fe-N interface structures. The adhesion between CrN/alpha-Fe interface is affected by the thickness of the CrN film. When the thickness of the CrN film is 5 angstrom, both tensile and shear forces are the largest, which are 1245.964 nN and 198.346 nN, respectively. In the nano-indentation simulation of CrN film with a thickness of 5 angstrom and alpha-Fe matrix, it is found that the larger the loading speed is, the larger the maximum load is. The hardness of the CrN film is increased linearly with the increase of the loading speed. When the speed is 50 m/s, the hardness is 13.33 GPa; when the speed is increased to 130 m/s, the hardness is also increased to 19.73 GPa. (C) 2019 Elsevier B.V. All rights reserved.