Effect of structural evolution on mechanical properties of ZrO2 coated Ti–6Al–7Nb-biomedical application

Abstract Zirconia (ZrO 2 ) nanotube arrays were fabricated by anodizing pure zirconium (Zr) coated Ti–6Al–7Nb in fluoride/glycerol electrolyte at a constant potential of 60 V for different times. Zr was deposited atop Ti–6Al–7Nb via a physical vapor deposition magnetron sputtering (PVDMS) technique. Structural investigations of coating were performed utilizing X-ray diffraction (XRD) analysis. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) were used to characterize the morphology and microstructure of coatings. Unannealed ZrO 2 nanotube arrays were amorphous. Monoclinic and tetragonal ZrO 2 appeared when the coated substrates were heat treated at 450 °C and 650 °C, while monoclinic ZrO 2 was found at 850 °C and 900 °C. Mechanical properties, including nanohardness and modulus of elasticity, were evaluated at different annealing temperatures using a nanoindentation test. The nanoindentation results show that the nanohardness and modulus of elasticity for Ti–6AL–7Nb increased by annealing ZrO 2 coated substrate at 450 °C. The nanohardness and modulus of elasticity for coated substrate decreased with annealing temperatures of 650, 850, and 900 °C. At an annealing temperature of 900 °C, cracks in the ZrO 2 thin film coating occurred. The highest nanohardness and elastic modulus values of 6.34 and 218 GPa were achieved at an annealing temperature of 450 °C.