Bioactive calcium phosphate invert glass-ceramic coating on β-type Ti–29Nb–13Ta–4.6Zr alloy

A fine, strong coating consisting of a bioactive calcium phosphate invert glass-ceramic can be prepared easily by reaction of the glassy phase with an oxide layer formed on a new β-type titanium alloy, Ti–29Nb–13Ta–4.6Zr, when the metal, on which the mother glass powders with a composition of 60CaO–30P2O5–7Na2O–3TiO2 in mol% are placed, is heated at 800°C in air. A compositionally gradient layer is developed on the titanium alloy during the heating. Tensile bonding strength of the coating to the metal is significantly higher than those of the coatings to conventional metals such as Ti–6Al–4V alloy or pure titanium. The oxidized layer on Ti–29Nb–13Ta–4.6Zr alloy is relatively thinner than that on Ti–6Al–4V alloy even with heat treatment in air; large tensile stresses are not generated in the layer.