Microstructure and mechanical properties of additively manufactured GH4099 superalloy

Abstract

GH4099, a nickel-based superalloy, is widely used in high-temperature applications. Specimens were fabricated using laser-directed energy deposition (LDED) and conventional forging for comparison. Their microstructure and mechanical properties were examined in the as-fabricated condition and after heat treatment consisting of solutionizing at 1,100°C for 2 h followed by aging at 700°C for 8 h. LDED samples exhibited coarse, columnar grains aligned with the build direction, whereas forged samples showed fine, uniform equiaxed grains. After heat treatment, all samples showed significantly reduced grain size. Uniform Ni3(Al,Ti) precipitates formed at grain boundaries and within grains, contributing to boundary pinning and inhibition of grain growth. This microstructural refinement enhanced thermal stability and impeded dislocation motion. As a result, heat treatment markedly improved both hardness and tensile strength in all specimens. In particular, the heat-treated LDED specimen (LDED-3) achieved a tensile strength of 901.6 MPa and a hardness of 404.7 HV0.2, whereas the forged specimen (F-3) reached 1,176.3 MPa and 397.1 HV0.2, respectively. The forged sample displayed the highest tensile strength, while the heat-treated LDED specimen exhibited the highest hardness. These findings demonstrate that optimized heat treatment can significantly refine the microstructure and improve the performance of GH4099 alloy, providing valuable guidance for the production of high-performance nickel-based superalloy components for high-temperature applications.

Keywords

Laser-based directed energy deposition / Nickel-based superalloy / Heat treatment / Microstructure / Mechanical properties

Funding

This work was financially supported by the National Natural Science Foundation of China (grant number 52405433), the Fundamental Research Program of Shanxi Province (grant number 202403021212119), the China Postdoctoral Science Foundation (grant number 2024M763031), and Shanxi Provincial Key Research and Development Program (grant number 202102050201009); Shanxi Scholarship Council of China (grant number 2024-116).

Conflict of Interest

The authors declare that they have no competing interests.

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