Tantalum coated NiTi alloy by PIIID for biomedical application

Plasma immersion ion implantation deposition (PIIID) technique was employed to fabricate tantalum coatings on NiTi alloys with the aim to obtain a more adherent, corrosion resistant and radiopaque coatings in our present study. The surface characteristics and corrosion behavior were investigated by SEM, AFM, XRD, AES, XPS and electrochemical measurement. The results show that a relatively rough, dense and adhesive tantalum coating has been successfully fabricated on NiTi alloy by the PIIID method with the thickness of about 3.3 μm. The surface topography of the tantalum coatings is characterized by regularly spaced grain facets. The coating is combined with a mixture of predominantly α-phase tantalum with a small concentration of β-phase tantalum. The outmost surface of the coating is oxidized, consisting of majority of stoichiometric Ta2O5 and a small quantity of Ta2O5 − X. It can be concluded that the dense and adhesive tantalum coatings on NiTi alloy improve its corrosion resistance, implying the decrease of Ni ions released into human body fluids.

► A dense and adhesive tantalum coating has been successfully fabricated on NiTi alloy by PIIID.
► The coating is combined with a mixture of predominantly α-phase tantalum with low concentration of β-phase tantalum.
► Tantalum coating has improved the corrosion resistance of NiTi alloy.