NIMS and Osaka University 3D Print Nickel Single Crystals Using PBF Laser

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NIMS and Osaka University Graduate School of Engineering have successfully used 3D printing to fabricate a nickel single crystal with only very few crystal defects by irradiating nickel powder with a flat laser beam at large Ray. Their research has been published in Additive Manufacturing Letters, an open access journal.

The nickel single crystal, with only very few crystal defects, was obtained by irradiating nickel powder with a large radius flat laser beam (i.e. a laser beam whose intensity is uniform over a beam cross-section). This technique can be used to make a wide variety of single crystal materials, including heat resistant materials for jet engines and gas turbines.

Previous studies have reported that single crystals can be fabricated using electron beam additive manufacturing. However, this technique requires expensive equipment and its operation is also expensive due to the need to create a vacuum, which limits its generalization. Although laser additive manufacturing can be done using less expensive equipment, previous efforts to manufacture single crystals using this technique had failed.

When a raw metal powder material is irradiated with a laser beam, it melts, forming a solid-liquid interface. It had been difficult to grow grains near the interface in the same direction and prevent the formation of strain-inducing defects caused by their solidification. This problem was found to be attributed to the intensity profile of conventional Gaussian laser beams (i.e. laser beams with a bell-shaped intensity over a cross-section of the beam), which causes polycrystals to form. composed of less oriented crystal grains with many grain boundaries.

Using a commercial SLM 280 3D printer from SLM Solutions, the research team from the Graduate School of Engineering at NIMS University in Osaka successfully fabricated single crystals using a laser beam flat, forming a flat molten puddle surface on nickel powders. The individual crystal grains grew in the same direction with fewer strain-inducing defects. Single crystals without grain boundaries, which are prone to cracking, are very resistant to high temperatures.

From left to right: laser beam irradiated on the powder bed and the resulting cylindrical single crystal objects produced. (Right) A flat laser beam can be applied to form aligned crystals in the same orientation while the application of a conventional Gaussian laser beam results in less oriented crystal grains.

This new technique makes it possible to minimize the generation of stresses and the cracking of the crystals during their solidification. In addition, this technique does not require the use of seed crystals, which simplifies additive manufacturing processes. In addition to nickel, this laser additive manufacturing technique can be used to transform other metals and alloys into single crystal objects.

Jet engine and gas turbine components are becoming increasingly complex and lightweight, and the demand for additive manufacturing of these components using heat-resistant nickel-based superalloys is growing. Because single crystals are stronger than polycrystals at elevated temperatures, their practical use as heat-resistant materials holds promise. Global R&D efforts to achieve this using cheaper and widely used laser additive manufacturing technology are expected to rapidly intensify.

This project was carried out by a research team consisting of Dennis Edgard Jodi (Junior Researcher, NIMS; PhD Student, Kyushu University), Tomonori Kitashima(Open in a new window) (Senior Researcher, NIMS; Associate Professor, University of Kyushu ), Makoto Watanabe(Open in a new window) (Director of Bonding and Fabrication Field, NIMS), Takayoshi Nakano (Professor, Graduate School of Engineering, Osaka University) and Yuichiro Koizumi (Professor, Graduate School of Engineering, Osaka University).

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