Enhancing wear resistance: In-situ ceramic phase precipitation for strengthening and toughening FeCoNiCrNx high-entropy alloy films

FeCoNiCr high-entropy alloys have attracted widespread attention because of their excellent toughness; however, their insufficient hardness limits their application in wear-resistant films. The introduction of non-metallic elements is an effective method for strengthening high entropy alloys films. In this study, high-entropy alloy films of FeCoNiCrNx with varying nitrogen content were fabricated using reactive magnetron sputtering. The influence of nitrogen content on the structure, mechanical properties, and tribological behavior of these high-entropy alloy films was studied. With an increase in nitrogen content, the FeCoNiCrNx film undergoes amorphization and simultaneous precipitation of Cr2N phases. At lower nitrogen flow rates (0-4 sccm), the film exhibits lower hardness (8.51-10.97 GPa) and poor wear resistance. At moderate nitrogen flow rates (8 sccm), the film exhibits enhanced hardness (12.8 GPa) and toughness, leading to favorable wear resistance (4.04 x 10-6 mm3 N-1 m-1). A further increase in the nitrogen flow rates (12-16 sccm), while raising hardness (13.08-15.17 GPa), leads to a slight reduction in toughness and consequently, a mild decrease in wear resistance (4.37-5.09 x 10-6 mm3 N-1 m- 1). A biphase structure design combining FeCoNiCr high entropy alloy and ceramic (Cr2N) improved the strength and toughness of FeCoNiCrNx and significantly enhanced its wear resistance, thus enhancing its application potential.