Electrochemical behavior of TiAlSiN hard coatings synthesized by a multi-plasma immersion ion implantation and deposition technique

• Microstructure and electrochemical behavior of TiAlSiN coatings are presented.
• Al addition induces serious lattice distortions and dislocations.
• Si incorporation induces an obvious grain refinement effect.
• TiAlN coating shows a higher corrosion rate than the TiN coating.
• TiAlSiN coating with higher Si content shows better corrosion resistance.

The TiAlSiN coatings are synthesized by a multi-plasma immersion ion implantation and deposition technique. The microstructure and the electrochemical behavior of the as-deposited coatings are investigated by using X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and electrochemical tests. These studies reveal that huge lattice distortions and dislocations emerge in the coating after introducing a small amount of Al component. These structural defects can facilitate the corrosion process of the TiAlN coating. The TiAlN coating exhibits a worse corrosion resistance performance than the TiN coating. The TiAlSiN coating has a two phase microstructure, nc-TiAlN/a-Si3N4. The grain size is greatly reduced after introducing Si component, whereas the portion of the a-Si3N4 phase increases as the amount of Si increases in the coating. The reduced grain size and the increased percentage of the a-Si3N4 phase in the TiAlSiN coatings enhance their ability in corrosion resistance. The TiAlSiN coating with a larger amount of Si shows better corrosion resistance performance. This research provides a comprehensive understanding of the relationship between the microstructure and the electrochemical behavior of the TiAlSiN hard coatings.