A new approach to develop palladium-modified Ti-based alloys for biomedical applications

A new powder mixing/coating technique combined with selective laser melting (SLM) or hot isostatic pressing has been used to modify Ti-6Al-4V (Ti64) with Pd with the aim of further improving its corrosion resistance. The modified alloy samples were characterised in terms of porosity, surface structure, microstructure and composition using optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and electron microprobe analysis (EPMA). Their corrosion properties were evaluated via electrochemical tests and the mechanical properties measured via tensile tests. Using a new physical powder mixing technique, Pd was homogeneously distributed among the base Ti alloy powder particles without damaging their sphericity. After HIPing Pd is mainly located at grain boundaries while during SLM Pd has dissolved into the matrix. The porosity in the as-SLMed samples and surface roughness both increase continuously with increased laser scanning speed. Pd did not cause significant improvement in tensile properties but did enhance corrosion resistance in 2 M HCl by shifting the corrosion potential into the passive region of Ti64. The current work suggested that the new approach is a feasible route of synthesising modified alloys with both chemical and microstructural homogeneity as well as improved performance for biomedical application.