Directed energy deposition (DED) of Inconel 939 (IN939) alloy is useful for fabricating and repairing geometrically complex components used in gas turbine systems. Repeated laser scanning produces a non-equilibrium microstructure that can support high mechanical strength. However, because the microstructure of DED IN939 differs from that of conventionally manufactured IN939, it may evolve differently under the same post-heat-treatment conditions. Therefore, this study applied different aging temperatures to investigate the microstructural evolution and mechanical properties of DED IN939 alloys and to identify suitable post-heat-treatment conditions. Quantitative microstructural characterization showed that both the γ′ phase fraction and γ′ size increased as the first and second aging temperatures increased. Consistent with γ′ evolution under the different aging conditions, specimen strength was positively correlated with aging temperature, whereas elongation decreased because excessive γ′ formation and growth narrowed the γ′ channel width. Consequently, aging at 840 °C for 8 hours followed by aging at 740 °C for 8 hours provided the best combination of high strength and ductility in room-temperature tensile tests.

1. Introduction 
2. Experimental 
    2.1. Materials 
    2.2. DED processing parameters 
    2.3. Post-heat treatment 
    2.4. Microstructure Characterization 
    2.5. Mechanical Properties 
3. Results and Discussion 
    3.1. Microstructure 
    3.2. Mechanical Properties 
4. Conclusion 
Funding
Conflict of Interest 
Data Availability Statement 
Author Information and Contribution 
Acknowledgments
References

• 김영우(경상국립대학교 나노신소재융합공학과) | Youngwoo Kim (Department of Materials Engineering and Convergence Technology, Gyeongsang National University, Jinju 52828, Republic of Korea)
• 성예찬(경상국립대학교 나노신소재융합공학과) | Ye Chan Sung (Department of Materials Engineering and Convergence Technology, Gyeongsang National University, Jinju 52828, Republic of Korea)
• 강호성(경상국립대학교 나노신소재융합공학과) | Ho Seoung Kang (Department of Materials Engineering and Convergence Technology, Gyeongsang National University, Jinju 52828, Republic of Korea)
• 김정기(경상국립대학교 나노신소재융합공학과) | Jung Gi Kim (Department of Materials Engineering and Convergence Technology, Gyeongsang National University, Jinju 52828, Republic of Korea) Corresponding author