Globular surface layer in electron beam powder-bed fusion Ti-6Al-4V after standard powder removal blasting and hot isostatic pressing

Abstract

A globular α recrystallization has been discovered at the surface of net shape electron beam powder-bed fusion (PBF-EB) Ti-6Al-4V alloy parts. This recrystallization is the result of powder recovery blasting followed by hot isostatic pressing treatment (HIP), which mimics the thermomechanical treatment necessary to achieve globularization in wrought Ti-6Al-4V. The thickness of the globular surface α is variable depending on the blasting intensity as well as the presence of surface protrusions that block the line-of-sight of the blasting media. The globular layer contains a 0001 orientation relationship parallel to the blasting direction, plus a low intragranular orientation deviation, when compared to the bulk. The results indicate that this globular α at the surface may be present for all net-shape Ti-6Al-4V components that have been manufactured via PBF-EB and subjected to a HIP treatment. Tunable fatigue and wear performance may be possible through controlled blasting parameters and globular surface layer thickness.