Low voltage environmentally friendly plasma electrolytic oxidation process for titanium alloys.

Area of Science:

• Materials Science
• Surface Engineering
• Electrochemistry

Background:

• Plasma electrolytic oxidation (PEO) is a key surface treatment for protecting light metals like Mg, Al, and Ti.
• Titanium alloys require robust surface coatings for enhanced performance and durability.

Purpose of the Study:

• To develop an environmentally friendly PEO process for titanium alloys using nitrogen-containing electrolytes.
• To investigate the effect of nitrogenation on the properties of PEO-generated oxide coatings on T1 titanium alloy.
• To characterize the composition, morphology, and properties of the resulting composite coatings.

Main Methods:

• Utilized a low-voltage (120 V) plasma electrolytic oxidation process with nitrogen-containing electrolytes.
• Formed approximately 12-micron thick oxide coatings on T1 titanium alloy surfaces.
• Compared coatings produced with and without nitrogen-containing compounds, analyzing morphology, composition, hardness, and corrosion resistance.

Main Results:

• Achieved uniform, adherent, and porous oxide coatings with basalt-like morphologies.
• Identified coatings as composites of titanium oxides, silicates, and, with nitrogenation, titanium carbide (TiC) and titanium nitride (TiN).
• Demonstrated the single-bath production of TiₓOᵧ, Ti-Si-O, TiC, and TiN composite coatings without external nanoparticles.
• Observed improved hardness with nitrogenation, but also stress-induced cracking, potentially reducing corrosion resistance.

Conclusions:

• The study presents a novel, single-bath PEO method for creating complex titanium oxide composite coatings.
• Nitrogenation enhances coating hardness but can compromise corrosion resistance due to induced cracking.
• The resulting coatings exhibit visible light functionality, suggesting potential optoelectronic applications.