Additively manufactured NiTi shape memory alloys are promising for biomedical devices, but their rough and defect-rich surfaces can destabilize the passive film, accelerate corrosion, and promote sustained Ni release. In this study, pure Ti coatings were deposited on additively manufactured NiTi alloy by direct-current magnetron sputtering, and the effect of substrate temperature on coating structure and long-term protective behavior was investigated. The results revealed that substrate temperature significantly affected crystallographic orientation, grain growth, coating compactness, corrosion resistance, and Ni-blocking performance. The coating deposited at 250 °C showed the best overall performance, with a hardness of 8.24 GPa and the lowest corrosion current density of 9.79 × 10 ⁻⁸ A·cm ⁻² . After 35-day immersion tests in Hank’s solution, the cumulative Ni release decreased to 0.0186 μg·cm ⁻² , corresponding to an inhibition efficiency of 94.66% compared with the uncoated additively manufactured NiTi sample. Post-immersion surface and XPS analyses showed that this superior performance resulted from a denser Ti barrier layer and a more stable TiO ₂ -dominated passive film. These results identify substrate temperature as a key processing variable for improving the long-term surface safety of additively manufactured NiTi alloy.

The effect of thermomechanical processing (TMP) parameters on the structural-phase evolution and properties of Ni-enriched Ti–50.8 at.% Ni shape memory alloy was investigated. Compression deformation was performed at T = 300–500 °C, accompanied by the development of dynamic aging (DA) processes, to true strains of e = 0.5–1.3, followed by post-deformation static aging (SA) at 430 °C for 1 and 10 h. The structural-phase state and properties were characterized using optical and transmission electron microscopy, X-ray diffraction, differential scanning calorimetry, and Vickers hardness measurements. The results confirmed that DA processes were activated during compression but proved insufficient for pronounced Ti₃Ni₄ precipitate growth compared with SA. The temperature range of 430–500 °C promoted the most intensive DA processes and facilitated ultrafine-grained structure formation. The processing route combining DA at 500 °C with short-term SA (1 h) resulted in the finest precipitates of Ti₃Ni₄ phase and most homogeneous substructure. These findings demonstrate that the proposed TMP strategy enables effective tailoring of precipitate dispersion, evolution of transformation temperatures and mechanical properties (hardness), providing a viable manufacturing pathway for tailoring TiNi SMA performance in advanced biomedical and engineering applications.