Effect of ceramic types on the microstructure and corrosion behavior of titanium matrix composites produced by selective laser melting

Abstract

To find out which ceramic particles can efficiently improve the corrosion resistance of commercial pure titanium (CP-Ti), the ex-situ formed Ti-2.5TiN composite and in-situ synthesized Ti-2.5TiB composite were developed by selective laser melting (SLM) and their corrosion behavior in 3.5 wt% NaCl solution was investigated. The open-circuit potentials, polarization curves, and electrochemical impedance spectroscopy were measured and compared. The results demonstrated that the corrosion resistance of SLM-produced Ti-2.5TiB composite possesses is better than that of the SLM-produced Ti-2.5TiN and CP-Ti samples after immersion for 0 day (without immersion). Due to tiny TiB and TiB 2 particles acting as the micro-cathode in the titanium matrix, anodic dissolution of the titanium matrix was prominently facilitated in the early corrosion stage, followed by rapid passivation on the surface of the titanium matrix. However, the corrosion resistance of SLM-produced Ti-2.5TiN composite possesses is better than the SLM-produced Ti-2.5TiB and CP-Ti after immersion for 5 and 10 days. The fine grain size, the δ-TiN phase, and the higher relative density can help the Ti-2.5TiN surface to form a stable passive film. • CP-Ti, Ti-2.5TiN and in-situ Ti-2.5TiB composites are produced by selective laser melting. • Ti-2.5TiN has higher relative density and finer grain size than Ti-2.5TiB composite. • Secondary passivation behavior confirms that the passive film is a double-layer structure. • Refinement grains and δ-TiN phase improve corrosion resistance of Ti-2.5TiN. • The effect of ceramic particle types on the corrosion resistance of CP-Ti was discussed.