Molecular dynamics investigation of friction properties in FeCoNiTi high-entropy alloy coatings on titanium substrate

Titanium (Ti) and Ti alloys are widely used in many important fields due to their excellent mechanical properties and corrosion resistance. However, due to their poor wear resistance, they are difficult to adapt to the complex service environment. The wear resistance of titanium-substrate materials can be effectively improved through surface coating technology. The friction performance of Ti-substrate Fe_0.05Co_0.4Ni_0.5Ti_0.05 high-entropy coating was investigated by molecular dynamics. The results show that the increase of friction depth D has a great influence on the tangential force and normal force, and leads to the increase of friction coefficient. The friction velocity V has limited effects on the tangential force, normal force, and friction coefficient of the three interfaces. The (001)_HEA||(\(1\overline{1}\)00)_Ti interface model has the smallest friction coefficient, the best wear resistance, and the smallest maximum stacking height and atomic loss ratio. When subjected to friction, the HEA coating absorbs and releases stress and activates dislocations during this process. The stacking faults caused by dislocation movement are mainly located in the HEA coating. This mechanism reduces the stress and defect depth in the Ti matrix, and effectively prevents the damage caused by friction to the lattice structure of the Ti matrix. At the same time, a large number of stationary dislocations are generated during the friction process, and tangles are formed, resulting in work hardening and improving the strength and hardness of the coating.