Fatigue performance of shelled additively manufactured parts subjected to hot isostatic pressing

X-ray tomography study of “squeezed pores” in additively manufactured titanium alloy subjected to hot isostatic pressing

“…Laser powder bed fusion of Ti6Al4V (ELI) was used to manufacture samples, using an EOS M290 machine located at Executive Engineering Pty Ltd, South Africa. Hot isostatic pressing was performed at Quintus Technologies Inc (Sweden) and CT scans performed at Stellenbosch University as reported previously in [10][11][12]. In this work, synchrotron tomography was additionally performed at the ID19 beamline of the ESRF.…”

“…However, pores connected to the surface caused imperfect pore closure. This concept was utilized in subsequent work to increase the LPBF-HIP combined process productivity by manufacturing only shells and thereby saving significant laser processing time [11,12]. Despite the success of this approach, pore closure is not expected to be fully successful, as the argon gas is not soluble in the titanium matrix, hence "squeezed pores" still exist in this material, which is of interest here.…”

The role of scan strategies in fatigue performance for laser powder bed fusion

“…Post processing may be undertaken to negate the effects of defects within AM components. Hot Isostatic Pressing (HIP) has been reported as a means by which to enhance the integrity of components by partially sealing micro pores and cracks [7]. As a result, tensile strength and elongation to failure have been enhanced and mechanical properties approach that of wrought equivalents.…”

“…In LPBF, generally two types of defect are distinguished: i) entrapped gas due to vapour recoil during melt pool formation also known as keyholing and ii) lack of fusion caused by insufficient laser penetration or energy. Entrapped gas bubbles are typically spherical and small in size, while lack-of-fusion defects are irregularly shaped and often still include partially-or unmolten powder particles [4,7,11].…”

Failure Modes in Dual Layer Thickness Laser Powder Bed Fusion Components Using a Novel Post-Mortem Reconstruction Technique

“…Only processing the shell of components allows for significantly reduced lasing time during builds. However, this approach was not as successful when specimens were subject to fatigue testing for shelled [17] or highly porous parts [18]. Additionally, some complex geometries associated with LPBF, such as internal lattices and cooling channels, are not appropriate for the HIP process, since the geometry is expected to morph drastically due to large shrinkage during the HIP process.…”