Proceedings of the
9th International Conference of Asian Society for Precision Engineering and Nanotechnology (ASPEN2022)
15 – 18 November 2022, Singapore

Additive manufacturing of MoSi2 and NbSi2 products for ultrahigh-temperature structural materials

Koji Hagihara1,2 and Takayoshi Nakano1,3,a

1Osaka University Anisotropic Design & AM Research Center, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan

2Department of Physical Science and Engineering, Nagoya Institute of Technology, Gokiso, Nagoya 466-8555, Japan

3Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan


Transition metal disilicides such as C11b-MoSi2 and C40-NbSi2 are promising candidates for ultrahigh-temperature structural materials aiming at the use over 1200°C. However, their product fabrication has been limited owing to their significant brittleness. To overcome this, we have tried the additive manufacturing (AM) of their products via selective laser melting. As a result, we have succeeded their shape control by the appropriate selection of process parameters. In addition, strong texture control was achieved in them. It is to note here that the crystallographic features of the developed texture were different from those observed in cubic materials such as Ni-based superalloys and beta-Ti for biomedical implant. By the unidirectional scanning of the laser (X-scan), single crystalline texture in which [001] is aligned along the scanning direction could be developed in MoSi2, which possibly results in the fabrication of the products with better high-temperature strength. However, in the directional scanning with a subsequent rotation of 90° for each layer (XY-scan), only fiber-like texture in which <100] is weakly aligned along the building direction was developed. In case of NbSi2, on the other hand, the development of the so-called basal fiber texture wherein <0001> was parallel to the building direction was achieved in any scanning strategies, and the single crystalline texture was not developed. The C11b-MoSi2 and C40-NbSi2 have the tetragonal and hexagonal unit cell, respectively. A comparison of these results led us to the conclusion that crystal symmetry, i.e., the multiplicity of the preferential crystal growth direction, is one of the primary factors that governs the features of the textures developed in AM-built materials.

Keywords: Transition metal alloys and compounds, Selective laser melting (SLM), Crystallographic texture, High-temperature structural material.

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