Improved Corrosion and Long‐Term Immersion Behavior in 3.5 wt% NaCl Solution of Laser Powder Bed Fusion Produced Ti5Cu After Heat Treatment

Abstract

This work investigates the corrosion behavior and mechanism of laser powder bed fusion produced (LPBFed) Ti5Cu and its heat‐treated counterparts in 3.5 wt% NaCl solution. The results indicate that heat treatment can enhance the corrosion resistance of LPBFed Ti5Cu by generating Ti2Cu phase, and heat treatment at higher temperature enhances corrosion resistance by forming a stable oxide film with a lower electron diffusion rate. The existence of Ti2Cu phase in the heat‐treated sample acts as the microanode that decelerates the corrosion on α‐Ti phase (prior dissolution of Ti2Cu phase). The long‐term immersion test results also confirm that the Ti2Cu phase present in HT900 (at higher heat‐treatment temperature) provides a better protective effect against corrosion compared to the one in HT740 and as‐LPBFed samples. Compared with the heat‐treated counterparts, the worst corrosion resistance of the as‐LPBFed Ti5Cu is attributed to that the acidic environment (e.g., Cl−) increases the electron diffusion rate in the film/solution interface, which makes the thermodynamically unstable α'‐Ti phase be preferentially corroded.

Structural, Electrical and Corrosion Properties of Bulk Ti–Cu Alloys Produced by Mechanical Alloying and Powder Metallurgy

“…This indicates a resistive nature corresponding to the solution resistance between the working and reference electrodes [31]. In the PBS and Ringer medium and low-frequency range (from 10 3 to 10 −1 ), the Bode phase plot (Figure 6b) exhibited one-time constants within the frequency range of 10 0 to 10 2 Hz [32][33][34]. This observation aligns with the anticipated one-layer structure of the passive film.…”

“…The magnitudes of resistances for the barrier layer decrease with increasing copper concentration. Reducing the resistance of the electrical double layer resulted in the sample surface exhibiting lower resistance to the infiltration of corrosive ions, such as Cl − , onto the TiCu substrate [34]. The magnitudes of capacitances for the barrier layer increase with the concentration of copper.…”