On the microstructure and tensile property of core-shell structured nickel-based superalloy part produced by laser powder bed fusion and hot isostatic pressing

Laser powder bed fusion (LPBF) has been increasingly used by industries to produce metal components. However, there remains a challenge to improve the productivity of the LPBF process, especially for high-volume production. In this study, we used Hastelloy-X (HX) as an example and demonstrated a hybrid approach of using a core-shell structured (0.5 mm thick dense shell + fast scanned porous core) part combining hot isostatic pressing (HIP) to improve the LPBF productivity. The microstructure evolution, mechanical properties, and the production rate of the parts built with and without the core-shell structure are compared and discussed in this work. The as-built core-shell HX showed a porous core enclosed by a dense shell, the density was restored through HIP. The HIP-processed core-shell HX revealed an artificially induced grain size gradient (large to small) from the shell to the core, while the HX without the core-shell structure presented uniformly distributed larger grains in the microstructure after HIP. The mechanical properties were studied using microhardness tests and uniaxial tensile tests. The core-shell HX showed an increment of the microhardness from the shell to the core, and the corresponding tensile properties were superior to the HX without the core-shell structure. The LPBF production rate using the core-shell approach was largely improved than the equivalent solid production route. The findings herein demonstrate the feasibility of using the core-shell approach to improve the productivity of the LPBF HX without sacrificing the tensile properties.