Efeito da composição e da sinterização na microestrutura e na resistência à corrosão de ligas Ti-Si-B

Abstract

Titanium alloys are widely used for dental, medical, automotive/aeronautic/aerospace applications due to their chemical, physical, biological and mechanical properties. Orthopedic dental implants of the alloy Ti–10Si–5B present good bone integration capacity as well as the Tiss +Ti6Si2B alloys exhibit higher oxidation resistance than the Tiss+Ti5Si3 alloys. In this way, this project aimed to evaluate the corrosion behavior of Ti-Si-B alloys using the potentiodynamic polarization methods in different medias: artificial saliva (AFNOR NF S90-701), simulated body fluid (SBF) and saline atmosphere (NaCl 3%). The alloys Ti-8Si-4B,Ti-10Si-5B, Ti-14Si-7B, Ti-20Si-10B and Ti-22Si-11B were produced by high-energy ball milling and sintered by two different routes: (a) conventional sintering and (b) spark plasma sintering (SPS). The alloys were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive spectrometry (EDS), confirming microstructures based on Tiss and Ti6Si2B phases. Porosity tests based on Arquimedes’ principle were also performed to evaluate the porosity and the density of the samples, which indicated that Ti-Si-B alloys produced by SPS demonstrated higher densification values. For Ti-22Si-11B alloy produced by conventional sintering, the corrosion process initiated faster and the density current at the active-passive transition is higher, which can be associated to the higher porosity. As expected, SPS technique produced denser Ti-Si-B alloys and finer microstructures. The Ti-22Si-11B alloy containing a higher amount of Ti6Si2B phase exhibited a lower value for passivation current density (0,08x10-6 A/cm2) and a higher corrosion potential (-0,232V) compared to Ti-8Si-4B alloy (-0,415V e 5,45x10-6 A/cm2), indicating a better corrosion resistance to all evaluated medias.