Laser-directed energy deposition of bioactive glass on Ti-6Al-7Nb titanium alloy substrate with highly refined grain structure

Abstract

The bioactive glass S520 was applied to an ultrafine-grained Ti-6Al-7Nb titanium alloy by a laser-directed energy deposition (LDED) process, in order to create a biocompatible material without potentially toxic vanadium for use in load bearing biomedical implants. The laser cladding process influenced the substrate's structure by melting the metallic material at the surface and infusing it with bioactive glass. Subsequently, the melted titanium alloy crystallised, resulting in the formation of relatively large grains. Deeper into the material, laser-induced heat triggered martensitic transformation, leading to the formation of α′ acicular martensite. In the lower regions of the HAZ, a distinctive band with refined grains was identified. Detection of certain amounts of Al directly in the bioactive glass raises concerns about potential toxicity as the glass dissolves in the human body. The nearly complete reduction in P concentration after 14 days highlights the high bioactivity of the material produced.