Controllable Preparation And Tribo-Corrosion Behavior Of VAlTiCrCu-based High-Entropy Alloy Film

In recent years,high-entropy alloys have received extensive attention and research due to their unique structure and excellent performance.At present,most of them are devoted to the research of as-cast high-entropy alloys,and there are relatively few studies on high-entropy alloy films.In this work,the VAlTiCrCu series high-entropy alloy thin films were successfully and controllably synthesized by magnetron sputtering using a novel spliced composite target which independently developed by the research group,and the effects of different deposition temperatures（100℃,200℃,300℃and 400℃）,nitrogen flow rate（0 sccm,100 sccm and 800 sccm）and annealing temperatures（700℃,900℃and 1100℃）on the microstructure and wear resistance of this series of high-entropy alloy films were systematically investigated.The main research results are as follows:（1）The VAlTiCrCu high-entropy alloy films with different deposition temperatures have a uniform element distribution and a single BCC phase.The mixed entropy,mixed enthalpy,atomic size difference,and valence electron concentration meet the high-entropy alloy thermodynamic criteria,which is attributed to the high solubility of Cr-Al,Ti-Al and V-Al,the complete miscibility of Cr-V and Ti-V,and the promotion effect of high entropy effect on their mutual solubility.（2）When the deposition temperature is 300℃,it promotes the diffusion and mutual dissolution of the elements,the structure of the film is dense and uniform,the hardness and elastic modulus reach the highest values of 10.93 GPa and 230.04 GPa.And the film shows good tribo-corrosion resistance:in 0.5mol/L H₂SO₄,the SO₄^2-hindered pitting nucleation and formed a dense passivation film,while the loose and porous corrosion products were formed in1.0 mol/L Na OH and the film were strongly pitted by Cl^-in 3.5 wt.%Na Cl.（3）The BCC phase of the nitrided VAlTiCrCu high-entropy alloy film disappears.After nitriding,the grain size is coarse,the structure is not as dense as the non-nitrided film,the thickness of the film is reduced,and its tribological performance and corrosion resistance are greatly reduced,especially when the nitrogen flow rate is 100 sccm.（4）Annealing treatment at 900℃and 1100℃promoted grain refinement and denser structure.The two phases of FCC and BCC coexisted,and their hardness/elastic modulus increased from 10.93 GPa/230.04 GPa to 13.81GPa/294.13 GPa and 12.49 GPa/285.07 GPa,respectively.The self-corrosion current density decreased from 3.34×10^-8 A/cm² to 2.29×10^-8 A/cm² and4.11×10^-9 A/cm²,respectively.The wear resistance and corrosion resistance are greatly improved.