Mechanical properties of biocompatible beta-type titanium alloy coated with calcium phosphate invert glass-ceramic layer

The presence of calcium phosphate invert glass-ceramic (designated as CPIG) layer on the surface of artificial implant products can improve the bonding between these products and bones. In this study, the morphology of the CPIG layer on the surface of a β-type titanium alloy, Ti-29Nb-13Ta-4.6Zr (TNTZ), was investigated for biomaterial applications by a dip-coating treatment. Furthermore, the mechanical properties of TNTZ coated with the CPIG layer were also investigated. In the CPIG layer, a compositionally gradient zone with a thickness of approximately 2.0 μm exists on the surface of the TNTZ. The titanium concentration in the zone increases with the decreasing distance from the CPIG surface toward the base materials. On the other hand, calcium and phosphorus concentrations in the zone increase with the distance from the TNTZ surface. The tensile bonding strength between TNTZ and the CPIG layer is 25 MPa and that between aged TNTZ and the CPIG layer is 18.6 MPa. For easily understanding the change in mechanical properties by a dip-coating treatment, the values of those on TNTZ and TNTZ coated with CPIG layer were shown as follows. The tensile strength increases remarkably by a dip-coating treatment as compared with that of as-solutionized TNTZ while the elongation is a reverse trend. Young's modulus of TNTZ and aged TNTZ coated with the CPIG increases by 15 to 27GPa after the dip-coating treatment as compared with that of as-solutionized TNTZ (approximately 60 GPa). The fatigue limit of TNTZ coated with the CPIG layer is nearly equal to that (approximately 300 MPa) of as-solutionized TNTZ. On the other hand, the fatigue limit of aged TNTZ coated with the CPIG layer is a 100 MPa higher than that of as-solutionized TNTZ.