Microstructure engineering of a nickel base superalloy manufactured by powder bed fusion
Nickel-based superalloy Inconel 725 (IN 725) has been known for its excellent resistance to corrosion and superior mechanical properties even at elevated temperatures. The material has been widely used in oil and gas, marine, and aerospace industries. However, when the alloy is subjected to hy...
| Main Author: | |
|---|---|
| Other Authors: | |
| Format: | Final Year Project (FYP) |
| Language: | English |
| Published: |
Nanyang Technological University
2022
|
| Subjects: | |
| Online Access: | https://hdl.handle.net/10356/159113 |
| _version_ | 1826117632257949696 |
|---|---|
| author | Ng, Darren Teng How |
| author2 | Matteo Seita |
| author_facet | Matteo Seita Ng, Darren Teng How |
| author_sort | Ng, Darren Teng How |
| collection | NTU |
| description | Nickel-based superalloy Inconel 725 (IN 725) has been known for its excellent resistance to
corrosion and superior mechanical properties even at elevated temperatures. The material has been
widely used in oil and gas, marine, and aerospace industries. However, when the alloy is subjected
to hydrogen-present environments, its mechanical properties tend to degrade in a phenomenon
called hydrogen embrittlement (HE). Through microstructure engineering, it may be possible to
enhance IN725’s resistance to HE. Σ3 coherent twin boundaries (CTB) are known to be
susceptible to crack initiation but are resistant to crack propagation in the presence of hydrogen.
In this project, near dense Σ3-rich and Σ3-free microstructures were manufactured by varying the
volumetric energy density during laser powder bed fusion. Σ3-rich microstructures (with 48%
CTB fraction and 82.7% recrystallized grain fraction) and Σ3-free microstructures (with 0.127%
CTB fraction and 2.1% recrystallized grain fraction) were successfully fabricated. Tensile tests of
the homogenous samples showed higher ductility in samples with Σ3-rich microstructure while
samples with Σ3-free microstructures yielded higher strength. Alternating Σ3-rich and Σ3-free
microstructured heterogeneous lamella samples were printed with increasing domain thickness.
Electron Backscatter Diffraction scans showed domains printed with 3 or less layers of 35μm
theoretical layer thickness were indistinguishable from each other. Average actual thicknesses of
the two microstructures per theoretical 35μm layer were also calculated. Σ3-rich microstuructured
domains tend to be thicker while Σ3-free microstuructured domains are thinner when compared to
the theoretical thickness. This suggests that the melt pool geometries for both microstructures are
different.
The data obtained from this project could pave the way for future works on heterogeneous lamella
microstructured superalloy components for applications in extreme environments. |
| first_indexed | 2024-10-01T04:30:29Z |
| format | Final Year Project (FYP) |
| id | ntu-10356/159113 |
| institution | Nanyang Technological University |
| language | English |
| last_indexed | 2024-10-01T04:30:29Z |
| publishDate | 2022 |
| publisher | Nanyang Technological University |
| record_format | dspace |
| spelling | ntu-10356/1591132023-03-04T20:08:18Z Microstructure engineering of a nickel base superalloy manufactured by powder bed fusion Ng, Darren Teng How Matteo Seita School of Mechanical and Aerospace Engineering mseita@ntu.edu.sg Engineering::Materials::Material testing and characterization Engineering::Mechanical engineering Nickel-based superalloy Inconel 725 (IN 725) has been known for its excellent resistance to corrosion and superior mechanical properties even at elevated temperatures. The material has been widely used in oil and gas, marine, and aerospace industries. However, when the alloy is subjected to hydrogen-present environments, its mechanical properties tend to degrade in a phenomenon called hydrogen embrittlement (HE). Through microstructure engineering, it may be possible to enhance IN725’s resistance to HE. Σ3 coherent twin boundaries (CTB) are known to be susceptible to crack initiation but are resistant to crack propagation in the presence of hydrogen. In this project, near dense Σ3-rich and Σ3-free microstructures were manufactured by varying the volumetric energy density during laser powder bed fusion. Σ3-rich microstructures (with 48% CTB fraction and 82.7% recrystallized grain fraction) and Σ3-free microstructures (with 0.127% CTB fraction and 2.1% recrystallized grain fraction) were successfully fabricated. Tensile tests of the homogenous samples showed higher ductility in samples with Σ3-rich microstructure while samples with Σ3-free microstructures yielded higher strength. Alternating Σ3-rich and Σ3-free microstructured heterogeneous lamella samples were printed with increasing domain thickness. Electron Backscatter Diffraction scans showed domains printed with 3 or less layers of 35μm theoretical layer thickness were indistinguishable from each other. Average actual thicknesses of the two microstructures per theoretical 35μm layer were also calculated. Σ3-rich microstuructured domains tend to be thicker while Σ3-free microstuructured domains are thinner when compared to the theoretical thickness. This suggests that the melt pool geometries for both microstructures are different. The data obtained from this project could pave the way for future works on heterogeneous lamella microstructured superalloy components for applications in extreme environments. Bachelor of Engineering (Mechanical Engineering) 2022-06-10T01:42:56Z 2022-06-10T01:42:56Z 2022 Final Year Project (FYP) Ng, D. T. H. (2022). Microstructure engineering of a nickel base superalloy manufactured by powder bed fusion. Final Year Project (FYP), Nanyang Technological University, Singapore. https://hdl.handle.net/10356/159113 https://hdl.handle.net/10356/159113 en A119 application/pdf Nanyang Technological University |
| spellingShingle | Engineering::Materials::Material testing and characterization Engineering::Mechanical engineering Ng, Darren Teng How Microstructure engineering of a nickel base superalloy manufactured by powder bed fusion |
| title | Microstructure engineering of a nickel base superalloy manufactured by powder bed fusion |
| title_full | Microstructure engineering of a nickel base superalloy manufactured by powder bed fusion |
| title_fullStr | Microstructure engineering of a nickel base superalloy manufactured by powder bed fusion |
| title_full_unstemmed | Microstructure engineering of a nickel base superalloy manufactured by powder bed fusion |
| title_short | Microstructure engineering of a nickel base superalloy manufactured by powder bed fusion |
| title_sort | microstructure engineering of a nickel base superalloy manufactured by powder bed fusion |
| topic | Engineering::Materials::Material testing and characterization Engineering::Mechanical engineering |
| url | https://hdl.handle.net/10356/159113 |
| work_keys_str_mv | AT ngdarrentenghow microstructureengineeringofanickelbasesuperalloymanufacturedbypowderbedfusion |