Structural Parameters and Behavior in Simulated Body Fluid of High Entropy Alloy Thin Films

Area of Science:

• Materials Science
• Corrosion Science
• Thin Film Technology

Background:

• High entropy alloys (HEAs) offer unique properties for various applications.
• Pulsed Laser Deposition (PLD) is a versatile technique for synthesizing thin films.
• Understanding the corrosion behavior of HEAs in physiological environments is crucial for biomedical applications.

Purpose of the Study:

• To investigate the structure, composition, and corrosion properties of AlCoCrFeNix HEA thin films.
• To evaluate the influence of nitrogen incorporation during PLD on film properties.
• To determine the suitability of these films for biomedical applications based on their corrosion resistance.

Main Methods:

• Synthesis of HEA thin films using Pulsed Laser Deposition (PLD) from VAR-produced AlCoCrFeNix targets.
• Deposition under residual vacuum and nitrogen atmosphere on Si and Ti substrates.
• Characterization using Grazing Incidence X-ray Diffraction (GIXRD), Scanning Electron Microscopy (SEM), X-ray Reflectivity (XRR), Energy Dispersive X-ray Spectroscopy (EDX), and X-ray Photoelectron Spectroscopy (XPS).
• Electrochemical evaluation in Simulated Body Fluid (SBF) using Open Circuit Potential (OCP) and Electrochemical Impedance Spectroscopy (EIS).

Main Results:

• Films exhibited face-centered cubic and body-centered cubic phases with a smooth surface containing droplets.
• Elemental composition closely matched target stoichiometry; nitrogen incorporation formed metallic nitride compounds.
• All films passivated in SBF, with HEN6 showing the most significant passivation and highest repassivation potential.
• HEN6 films displayed high corrosion resistance and acted as a physical barrier against corrosion for 24 hours in SBF.

Conclusions:

• The HEN6 HEA thin film, deposited under nitrogen, exhibits the most promising corrosion resistance and stability in SBF.
• PLD is effective in producing dense HEA films with tunable properties for potential biomedical applications.
• Nitrogen incorporation enhances the passivation and protective capabilities of HEA thin films in simulated physiological conditions.