Selective laser melting of Ti-TiN composites: Formation mechanism and corrosion behaviour in H2SO4/HCl mixed solution

Electrochemical measurements and microstructural analysis were performed to study the formation mechanism and corrosion behavior in mixed solution of the Ti-TiN composites produced by selective laser melting (SLM) and commercially pure titanium (CP-Ti) for comparison. The Ti-TiN composites comprise α′-Ti and δ-TiN, where the acicular α′ martensite is refined compared to that in the CP-Ti. The passive film of all samples comprises TiO2, Ti2O3 and TiO. Compared to CP-Ti, the Ti-TiN composites demonstrate higher corrosion resistance, owing to the fine grains, the initial rapid passivation and the corrosion shadow protection effect of the alloyed reaction layer on the α′-Ti.