Color tone and interfacial microstructure of white oxide layer on commercially pure Ti and Ti–Nb–Ta–Zr alloys

Abstract

In this study, the relationships among oxidation condition, color tone, and the cross-sectional microstructure of the oxide layer on commercially pure (CP) Ti and Ti–36Nb–2Ta–3Zr–0.3O were investigated. "White metals" are ideal metallic materials having a white color with sufficient strength and ductility like a metal. Such materials have long been sought for in dentistry. We have found that the specific biomedical Ti alloys, such as CP Ti, Ti–36Nb–2Ta–3Zr–0.3O, and Ti–29Nb–13Ta–4.6Zr, form a bright yellowish-white oxide layer after a particular oxidation heat treatment. The brightness L* and yellowness +b* of the oxide layer on CP Ti and Ti–36Nb–2Ta–3Zr–0.3O increased with heating time and temperature. Microstructural observations indicated that the oxide layer on Ti–29Nb–13Ta–4.6Zr and Ti–36Nb–2Ta–3Zr–0.3O was dense and firm, whereas a piecrust-like layer was formed on CP Ti. The results obtained in this study suggest that oxide layer coating on Ti–36Nb–2Ta–3Zr–0.3O is an excellent technique for dental applications.