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Microstructure and hot tensile behavior of Hastelloy X superalloy laser powder-bed fusion-fabricated through different scanning patterns

Tailoring the microstructure of the additively manufactured metal parts through adjusting process parameters is a useful pathway to reduce the necessity of post-treatments, leading to a reduction in cost and production steps. This work deals with the effects of scanning patterns on microstructures a...

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Published in:Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2023-03, Vol.867, p.144717, Article 144717
Main Authors: Kangazian, Jalal, Kermanpur, Ahmad, Shamanian, Morteza, Sadeghi, Fazlollah, Badrossamay, Mohsen, Foroozmehr, Ehsan
Format: Article
Language:English
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Summary:Tailoring the microstructure of the additively manufactured metal parts through adjusting process parameters is a useful pathway to reduce the necessity of post-treatments, leading to a reduction in cost and production steps. This work deals with the effects of scanning patterns on microstructures and hot tensile behavior of the laser powder-bed-processed Hastelloy X Ni-based superalloy at the as-built condition. Two scanning patterns of meander and island were used to build fully-dense specimens. The scanning transmission electron microscopy observations revealed the generation of dislocation-cell structure within the columnar austenitic grains. Dense-dislocation tangles and some Cr- and Mo-rich precipitates decorated the cell walls. Both meander and island specimens had almost the same crystallographic texture, average local misorientation, and average geometrically necessary dislocations density. However, the specimen employing the island scanning pattern had a larger grain size and cell size than the meander one. It was due to a lower cooling rate in the island specimens than in the meander one. It was found that although the room-temperature tensile properties of both specimens were not significantly different, the island specimen had superior tensile properties at high temperatures. However, the meander and island tensile specimens both underwent intergranular brittle fractures at 760 °C and 860 °C, leading to ductility loss at elevated temperatures. The fractography observations illustrated that combined influences of the weakening of the grain boundaries with an increase in temperature and the accumulation of dislocations resulted in intergranular cracking, leading to brittle fracture and ductility loss at high temperatures. •The effect of the scanning pattern on the microstructure-hot tensile property relationship of the laser powder-bed-fabricated Hastelloy X was investigated.•The island scanning pattern showed a lower cooling rate than the meander one, leading to larger grain and cell sizes.•The island scanning pattern resulted in superior hot tensile properties compared to the meander one.•The ductility of both island and meander tensile samples decreased by increasing the test temperature.•The weakening of the grain boundaries and the accumulation of dislocations were dominant factors responsible for ductility loss at high temperatures.
ISSN:0921-5093
1873-4936
DOI:10.1016/j.msea.2023.144717