Effect of post-treatment on the microstructure and tensile properties of Ni–Co-based superalloy manufactured by selective laser melting

ABSTRACT

A newly designed Ni–Co-based superalloy was manufactured by selective laser melting (SLM) and the effect of hot isostatic pressing (HIP) and heat treatment on the microstructure and tensile properties was investigated. The as-built sample showed epitaxial grains including sub-structures, whereas recrystallisation occurred in the HIP-treated samples. Furthermore, carbide particles appeared at the grain boundaries, and the γ’ phase formed extensively. The sample that was subjected to HIP-solution-treatment and aging (STA) contained a larger fraction of carbide and γ’ phase compared to the HIP sample, with a needle-shaped topologically close-packed (TCP) phase also generated inside the γ matrix. The yield and tensile-strengths increased by approximately 60% after HIP, and the elongation increased by 0.8%. However, the HIP-STA sample underwent a significant decrease in elongation by TCP phase. The correlation between the microstructure and mechanical properties of the SLM-built superalloy is also discussed on the basis of the fractography results.

KEYWORDS:

• Ni–Co superalloy
• selective laser melting
• microstructure
• tensile
• hot isostatic pressing

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The authors gratefully acknowledge the support of Korea Institute for Advancement of Technology grant funded by the Korea Government (MOTIE) ([grant number P0002007], The Competency Development Program for Industry Specialist).