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Laser Polishing of Nickel-Titanium Shape Memory Alloy Produced via Laser Powder Bed Fusion
Stanislav V. Chernyshikhin,Daniil V. Panov,Tran Van Tuan,Dmitriy Yu. Ozherelkov,Vadim A. Sheremetyev,Igor V. Shishkovsky 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.10
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 μm, and a laser spot of 500 μm. 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.
Mojtaba Jalali,Kaivan Mohammadi,Mohammad R. Movahhedy,Farzad Karimi,Sayed Khatiboleslam Sadrnezhaad,Stanislav V. Chernyshikhin,Igor V. Shishkovsky 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.9
Nitinol shape memory alloy is a biocompatible material that is suitable for biomedical applications due to its superelasticity,shape memory effect, good corrosion and fatigue resistance, and sound damping properties. With the selective laser melting(SLM) additive manufacturing process, it is possible to produce customized NiTi implants in the form of porous metamaterialswith complex geometries. This paper presents a review of modeling, production, and application of NiTi implants. First, the fundamentals of shape memory alloys and the SLM process are summarized. Then, the effects of the SLM processon the transformation temperatures and the impacts of Heat treatments on these temperatures for additive manufacturedparts are discussed. Next, a review of recent experimental works on the mechanical properties of NiTi lattice structures arepresented regarding the required functional properties of orthopedic implants. Also, in vitro and in vivo biological studies ofNiTi implants are reviewed. Finally, constitutive models developed for SMAs are presented and finite element simulationsof NiTi lattice structures are discussed.