Fabrication of porous titanium parts by powder bed fusion of Ti–TiH2 blended powder

Abstract

When a high-energy laser is used to irradiate Ti–χTiH2 blended powder, hydrogen gas (H2) is generated by the decomposition of the titanium hydride (TiH2) powder and serves as a pore-former and active agent. In this study, the powder bed fusion (PBF) of Ti–χTiH2 (χ = 2, 5, 10 wt.%) blended powder was used to innovatively fabricate porous titanium parts. The trapped H2 in the rapidly solidified molten pool produces porosity in the deposited layer. The PBF test results showed that the beam interaction time to generate H2 through the decomposition of TiH2 is important in controlling the porosity formation. As the content of TiH2 increases, the porosity increases owing to the increased amount of H2 generated from TiH2. Additionally, the porosity increases with increasing scan rate. The faster the scan rate, the more H2 is trapped, because the rapidly solidified molten pool does not provide sufficient time for H2 to diffuse out. The variation in porosity with subsequent layering in the PBF process was also investigated. The results of this study show that the porosity can be actively controlled by adjusting the TiH2 mixing ratio (χ) and the laser-processing parameters.