Microstructure and corrosion resistance of novel β-type titanium alloys manufactured by selective laser melting

Abstract

Due to its unique characteristics selective laser melting offers the possibility to manufacture highly complex and functional parts out of otherwise difficult processable materials. One example is β-type titanium alloys, which have very promising properties for various engineering applications. Two novel β-type alloys Ti–42Nb and Ti–20Nb–6Ta were compared with commercially pure titanium and Ti–6Al–4V ELI alloy in this study. All four lightweight materials were SLM-processed and the microstructure and corrosion resistance were investigated. While pure titanium and Ti–6Al–4V showed only the martensitic α′-phase, Ti–42Nb consists solely of the β-phase and Ti–20Nb–6Ta of the orthorhombic martensitic α″-phase. Potentiodynamic polarization showed a superior corrosion resistance for both β-type alloys, whereas Ti–42Nb performed slightly better than Ti–20Nb–6Ta. Released V and Al could be clearly observed for the Ti–6Al–4V ELI alloy by mass spectrometry due to corrosion processes, in contrast the release of Nb or Ta was hardly detected for the new alloys.

Keywords

• Titanium alloys
• Additive manufacturing
• Selective laser melting
• Microstructure
• Corrosion
• Corrosion products