Effect of crystal orientation on the nanoindentation deformation behavior of TiN coating based on molecular dynamics

In order to investigate the mechanism of nanoindentation deformation of TiN and the protective properties of TiN coating in [001] and [111] crystal orientation, molecular dynamics simulations were established for single-crystal TiN and bilayer TiN/FeCrNi models in this study. The hardness and reduced elastic modulus were obtained by analyzing the indenter load displacement curves obtained from the simulations. Combined with the atomic-scale analysis, it was found that the trigonal defect structure generated in the [111] crystal orientation of the single-crystal TiN enhanced the hardness of the material. The analysis of the simulation results of bilayer TiN/FeCrNi found that the coating withstood high stresses to effectively protect the substrate from damage, and the lower substrate hardness also improved the plastic deformation of the coating to avoid fragmentation, which showed basically the same hardness in both crystal orientations. The results of the study can provide theoretical support for the preparation and application of TiN coatings and provide useful insights to defect-formation, defect/defect interactions and plausible strengthening mechanisms upon loading.