Microstructure and Corrosion Resistance of Selective Laser-Melted TC4 Alloy

TC4 alloy samples were fabricated via selective laser melting (SLM) under different process parameters. The effects of scanning speed and build orientation on the microstructure and corrosion behavior were systematically investigated using optical microscopy (OM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), X-ray diffraction (XRD), and electrochemical measurements. The results show that when increasing scan speed, TC4 alloy consists primarily of α/α’ phases with a minor amount of β phase, along with grain refinement and a higher fraction of low-angle grain boundaries. In 3.5% NaCl solution, the XOY-oriented sample processed at 1000 mm s−1 exhibited higher impedance and formed a stable, highly protective passive film. In simulated body fluid, the XOY orientation at 1200 mm s−1 displayed a larger capacitive arc, indicating superior corrosion resistance. These findings demonstrate that the corrosion performance of SLM-processed TC4 alloy can be optimized for specific service environments by tailoring both process parameters and build orientation.