Preparation and characterization of TaCxN1 − x coatings on biomedical 316L stainless steel

In this paper, TaCxN1 − x coatings deposited on 316L stainless steel (SS) by RF magnetron sputtering at various substrate temperatures (Ts), were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), atomic force microscopy (AFM), scratch test and nanoindentation techniques. Then the corrosion resistance in phosphate buffered saline (PBS) and the hemocompatibility of the coating were further evaluated by potentiodynamic polarization, blood clotting test and platelet adhesion test. The substrate temperature (Ts) could significantly change the microstructure of TaCxN1 − x coatings. When Ts was less than 200 °C, the TaCxN1 − x coatings were in amorphous condition, whereas when Ts was increased to 200 °C, Ta2CN phase was formed, exhibiting in the form of fine particulates with the crystallite sizes of about 6–9 nm. The appearance of the nanocrystalline Ta2CN phase above 200 °C was associated with the pronounced increase in the hardness of TaCxN1 − x coating from 10 GPa to over 30 GPa. The scratch test results demonstrated that TaCxN1 − x coatings deposited above 200 °C exhibited good adhesion performance. The corrosion resistance of the 316L SS was improved significantly because of the deposited TaCxN1 − x coatings. The blood clotting test and the platelet adhesion test results indicated that the TaCxN1 − x coatings deposited at Ts of 25 °C and 200 °C possessed better hemocompatibility than the coating deposited at Ts of 400 °C.