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.