Joining of calcium phosphate invert glass-ceramics on a β-type titanium alloy

A bioactive calcium phosphate invert glass-ceramic containing beta-Ca-3(PO4)(2) crystals could be joined strongly with a Ti-29Nb-13Ta-4.6Zr alloy consisting of a beta-titanium phase by heating the metal on which the mother glass powders with a composition 60CaO(.)30P(2)O(5)(.)7Na(2)O(.)3TiO(2) (mol%) were placed, at 800degreesC for 1 h in air; the tensile joining strength was estimated to be similar to26 MPa on average. A compositionally gradient layer was developed on the metallic substrate during the heating. When the metal with glass powders on it was heated at 850degreesC in air, the phosphate glassy phase flowed viscously, permeating the oxide layer formed around the surface of the metal, which was thicker than that formed by heating at 800degreesC; a compositionally gradient layer was not developed, and a strong joining was not realized. The joining between the glass-ceramic and the metal is suggested to be controlled by viscous flow of the glassy phase in the glass-ceramic and by reaction of the glassy phase with the oxide phase formed around the surface layer of the metal.