Influence of Magnetron Sputtering-Deposited Niobium Nitride Coating and Its Thermal Oxidation on the Properties of AISI 316L Steel in Terms of Its Medical Applications

Abstract

An NbN coating was produced on AISI 316L steel using reactive DC magnetron sputtering. The effects of oxidation of the NbN coating in air on the microstructure, mechanical properties, corrosion resistance, contact angle and bioactivity were investigated. Phase composition was determined using X-ray diffraction (XRD), the coatings’ cross-sectional microstructure and thickness including surface morphology using a scanning electron microscope (SEM), microhardness via the Vickers method, corrosion by means of a potentiodynamic polarisation test in Ringer’s solution and bioactivity by observation in an SBF solution, while the contact angle was studied using a goniometer. The NbN coating and the oxidised coating were shown to demonstrate a Ca/P ratio close to that of hydroxyapatite, as well as increased microhardness and corrosion resistance. The best combination of mechanical, corrosion, bioactivity and hydrophilic properties was demonstrated by the air oxidised NbN coating, which featured an orthorhombic Nb2O5 structure in the top, surface layer.

Keywords

• NbN
• Nb₂O₅
• magnetron sputtering
• oxidising
• SBF
• microstructure