Laser Polishing of Nickel-Titanium Shape Memory Alloy Produced via Laser Powder Bed Fusion

Laser Powder Bed Fusion (LPBF) is considered a promising technology for NiTi intermetallic components production. However, different defects such as near-surface porosity inherent to the process are limiting the standardization and widespread of the technology due to the deterioration of the mechanical properties. In this work, a comprehensive study was implemented to reduce the near-surface porosity by the laser polishing of additively manufactured samples from pre-alloyed NiTi powder by LPBF. Different laser polishing process conditions were employed for the treatment of the near-surface region. Results have shown that the most effective treatment aimed at porosity healing occurs at a laser power of 540 W, a scanning speed of 25 mm/s, a hatch spacing of 200 mu m, and a laser spot of 500 mu m. The phase identification and martensite-austenite transformation temperatures characterization were carried out before and after the laser polishing of the NiTi samples; the influence of the laser polishing on the functional properties of the material was demonstrated. It was shown that the application of required linear energy density for successful healing of the near-surface porosity leads to the local solutionizing effect. Additionally, electrochemical studies were carried out in Hank's solution and demonstrated that the corrosion resistance was improved after laser polishing.