A review of the corrosion of laser nitrided Ti-6Al-4V

Purpose: The purpose of this paper is to consider the corrosion properties of laser nitrided Ti-6Al-4V alloys that have been reported previously by several researchers. Design/methodology/approach: Different kinds of surface nitriding methods of titanium alloys, such as plasma nitriding, ion nitriding, gas and laser nitriding, are introduced. Microstructure changes, such as phase formation and the influence of laser processing parameters in laser nitriding layers of Ti-6Al-4V alloys, were investigated using scanning electron microscope, transmission electron microscope, X-ray photo-electron spectroscopy, and X-ray diffraction. Based on investigations presented in the literature, the effect of laser nitriding on the corrosion behavior of Ti-6Al-4V alloy was reviewed. Findings: By regulating the laser processing parameter, the microstructure of the nitrided layer can be controlled to optimize corrosion properties. This layer improves corrosion behavior in most environments, due to the formation of a continuous TiNxOy passive film, which can retard the ingress of corrosive ions into the substrate and can maintain a constant value of a current density. Therefore, the laser gas nitrided specimens have a relatively noble corrosion potential and a very small corrosion current, as compared to untreated specimens. Originality/value: This paper comprises a critical review, and its collection of references is useful. It summarizes current knowledge in laser surface treatment research.