Abstract
In recent years, the opportunity of the hard tissues such as bones, hip joints and tooth to be replaced by metallic biomaterials is increasing. In general, metallic biomaterials lack bioactivity, which is the ability to directly form a chemical bond with bones. Therefore, the bioactive surface modifications on surface of metallic biomaterials have been investigated and applied. Among them, the calcium phosphate invert glass coating method, which is dip-coating treatment (DCT), can be granted the bioactivity on the surface of a β-type titanium alloy, Ti-29Nb-13Ta-4.6Zr (TNTZ) alloy, for biomaterial applications. In this study, aging characteristics and mechanical properties of TNTZ alloy surface-modified with DCT were investigated.
There is an oxide layer and α case near boundary between calcium phosphate invert glass layer and TNTZ surface in TNTZ surface-modified with DCT (TNTZDCT). A very fine ω phase precipitates in an equiaxed β phase with an average diameter of 20 μm at a distance of 200 μm from specimen surface. On the other hand, the microstructure of aged TNTZDCT has an α phase. The tensile strength of TNTZDCT is around 30% greater than that of as-solutionized TNTZ (TNTZST). On the other hand, the elongation is around 48% smaller than that of TNTZST. Tensile strength of aged TNTZDCT is around 26% greater than that of TNTZDCT. While the elongation of aged TNTZDCT is around 52% smaller than that of TNTZDCT. Fatigue limit of TNTZDCT is nearly equal to that of TNTZST. Fatigue limit of aged TNTZDCT is around 80 MPa greater than that of TNTZST. Fatigue limits of TNTZDCT and aged TNTZDCT, where their fatigue specimen surfaces are mirror-polished, rise as compared with those of TNTZDCT and aged TNTZDCT, where their fagigue specimen surfaces are shot-blasted.
