Effects of hot isostatic pressing treatment on the microstructure and tensile properties of Ni-based superalloy CM247LC manufactured by selective laser melting

This study manufactured CM247LC Ni-based superalloy, which has outstanding mechanical properties, using the laser powder bed fusion (L-PBF) method and selective laser melting (SLM). Furthermore, the effect of hot isostatic pressing (HIP) post treatment on the microstructure and mechanical properties of SLM-built CM247LC was investigated. The defect characteristics of SLM-built superalloy changed significantly according to scan speed and hatch space, and it achieved the optimal microstructure at an intermediate scan speed (600 mm/s). SEM, EBSD, and ECCI analyses of the as-built alloy identified grains that developed in the build direction, sub-grains consisting of dislocation networks and MC carbides. In addition, gamma' phase formed evenly throughout the sample after HIP post treatment. The as-built CM247LC showed a yield strength of 933.5 MPa and tensile strength of 1144.0 MPa. In the case of the HIP alloy, the yield strength remained at a similar level, but tensile strength increased significantly up to 1457.1 MPa, and tensile elongation increased four times compared to the as-built alloy. Based on the above findings, this study discussed the correlations between microstructure, improved tensile properties and deformation mechanism.

Automated summary

This study demonstrates that the CM247LC alloy manufactured using the L-PBF and SLM methods has excellent mechanical properties. The microstructure and mechanical properties of the SLM-built CM247LC alloy can be improved through HIP post treatment. The study also reveals that the defect characteristics of the alloy vary significantly with different scan speeds and hatch spaces, with the optimal microstructure achieved at an intermediate scan speed.