EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

In laser powder bed fusion (L-PBF), the mechanical performance of fabricated parts are significantly improved by hot isostatic pressing (HIP) as the density increases (pores are closed) and the microstructure improves. HIP ensures consistent and defect-free material, and consequently, this high-temperature and high-pressure process is often a requirement for safety-critical aerospace applications. The use of HIP to directly consolidate intentionally-unmelted interior powder in a L-PBF part was recently demonstrated. By confining the laser melting to only the outer shell (contour) of the structure, L-PBF production times can be dramatically reduced. A subsequent HIP cycle, which may be mandatory for reliability reasons, and therefore does not add additional costs, can then be used to densify the entire structure. Production rates and energy efficiencies can therefore be improved in this way. This presetnation describes the exploration of the effect of relying on the HIP process to consolidate interior sections of test coupons, for which micro computed tomography (microCT), process simulation and tensile tests were conducted. MicroCT of coupons with varying shell thicknesses identify the minimum shell thickness required; and provide indications of the shrinkage ratio as a function of powder content relative to shell thickness. Preliminary results are presented in which any shrinkage has been shown to be compensated for during design with deformation simulations. The simulations allow for accomodatin the 50-60% metal powder density and the consequent collapse as the powders are consolidated with HIP.