Overview of Inconel 939 Alloy Parts Developed by Additive Manufacturing Process

The related paper was published in Heliyon under the title "A systematic review of Inconel 939 alloy parts development via additive manufacturing process".

IN939 is a modern nickel based high-temperature alloy that can work continuously at high temperatures due to its excellent fatigue resistance, creep resistance, and corrosion resistance. The unique performance of IN939 is related to the composition of the alloy and specific post-treatment processes (such as solution treatment and aging treatment), resulting in features such as γ 'residues and MC and M23C6 carbides. This also includes the lack of eutectic and primary melting phases. For this alloy, the main component development is carried out through the powder bed melting process using a laser powder bed melting machine. Meanwhile, a separate study emphasized the synthesis of EB-PBF devices. The additive manufacturing process of these alloys is hindered by machine parameters, which have been found to be unable to obtain fully dense structures with the required properties alone. The purpose of these parameters is to improve its core performance while minimizing defects related to powder metallurgy processes, such as porosity, harmful precipitation, grain anisotropy, etc. This study aims to provide an overview of research progress related to IN939, with a clear focus on benchmarks achieved through additive manufacturing technology. Researchers discussed the work done in this field, compared the results of different studies, and identified gaps in current research. Through these works, researchers aim to gain a comprehensive understanding of the potential of IN939 and its applications in extreme environments.

Figure 1. Main aspects of developing IN939 components.

Figure 2. Microstructure of the casting sample.

Figure 3. Microstructure of the sample annealed at 1100 ℃ for 4 hours and then water quenched.

Figure 4. Main categories and software usage of additive manufacturing.

Figure 5. Simple schematic diagram of selective laser melting process for metal/alloy parts.

Figure 6. Schematic diagram of electron beam melting process.

Figure 7. Schematic diagram of direct energy deposition through (a) powder material feeding and (b) metal wire material feeding.

Figure 8. Schematic diagram of metal adhesive spraying process.

Figure 9. Fracture surfaces of (a) undisturbed specimen, (b) LTH specimen, (c) HTH specimen, and (d) cast LTH specimen subjected to creep rupture at 816 ℃/250 MPa.

Figure 10. Optical image of partially recast layer of the sample.

Figure 11. Scanning electron microscopy images of SLM samples (a, b) after aging without solution treatment, (c) after solution treatment+aging.

Figure 12. a, b) Cut the pit thickness and recast area of the sample. (c) Optical microscope images of the recast layer and HAZ area of CFG and (d) wire EDM methods.

Figure 13. Scanning electron microscopy microstructure images of the sample at different heights (b, c) 40mm, (d, e) 30mm, (f, g) 20mm, and (h, i) 10mm along the molding direction.

Inconel 939 additive manufacturing has been explored for advanced applications, which has led to further exploration of the impact of components and process parameters on this age hardening alloy. However, finished IN939 samples typically exhibit residual thermal strain, stress, and porosity, which may have a negative impact on their performance. To address these challenges, post-processing is considered crucial in achieving sample homogenization, controlling its microstructure, and reducing porosity. Although these processing methods have many benefits, they often require multiple steps and complex loops to form the required stages. These advances in AM and post-processing technology are expected to broaden the application range of IN939 parts and improve their performance in extreme environments. However, in addition to optimizing the microstructure and mechanical properties of IN939 parts, the performance of IN939 parts still needs to be further improved. Researchers can develop more targeted methods to optimize the performance of IN939 components and expand their potential applications by understanding their behavior in extreme environments rather than current developments. Combining hot isostatic pressing with optimized parameters at different stages of the multi-step heat treatment process can result in components with uniform microstructure and excellent isotropic mechanical properties.

Source: Yangtze River Delta Laser Alliance