Molecular Dynamics Investigation of Erosion Behavior and Mechanism of TiN Coatings at the Nanoscale: Implications for Wear in Oil Fracturing Environment

Due to its high strength and toughness, the TiN coating is considered one of the most promising coatings for resistance to particle impact and erosion wear in oil fracturing environments. In this study, based on the combined potential file of the Fe–Ti–N ternary system, nanoscale simulation models of TiN/Fe with different crystal planes ((001), (110), (111)) are established for the first time. Molecular dynamics simulations (MD) were used to investigate the effects and mechanisms of wear resistance and erosion resistance of the TiN coating under nanoscale indentation, scratching, and continuous impact. The difference in the surface properties of TiN coatings with different crystal faces is emphasized. The results indicate that there is no absolute best crystal plane. Due to the differences in molecular gaps between different crystal planes, surface groups on the lattice interface with the external environment, binding points between molecules within the lattice, types of forces, and modes of action, different crystal planes exhibit different surface properties under different wear forms. In the indentation and scratch stage, TiN(111) has better stability and greater hardness due to the structural advantages of its own triangular lattice, which can resist external loads, produce less wear debris, and basically does not appear with cracks and other surface damage except scratches. During the impact phase, TiN(001) exhibits greater elastic resilience, maintaining surface stability even after continuous particle impact.