Nanotechnologies / Materials
Aerospace, Energy

3D printing of TiAl turbine blades for aircraft engine
applications
Division of Materials and Manufacturing Science, Graduate School of Engineering
Associate Professor Ken Cho

https://researchmap.jp/choken

Professor Hiroyuki Yasuda

https://researchmap.jp/read0051691

Professor Takayoshi Nakano

https://researchmap.jp/read0013987

Nanotechnologies / Materials

Abstract
Metal-based 3D printing (3DP) has attracted much attention
since the process can build 3D objects by adding layer on layer ofmaterials. In the present study, we carried out systematic studies
on the fabrication of TiAl low-pressure turbine blades for aircraft
engines by electron beam powder bed fusion (EB-PBF). As a result, it was found that the microstructure of TiAl alloys depends
strongly on the process parameters such as beam current andscanning speed. Furthermore, the mechanical properties of TiAl alloys are closely related to the microstructure. In particular, at lower
beam currents and higher scanning speeds, the cooling rate is so
fast that microstructure evolution through massive transformation
occurs, resulting in excellent high temperature strength, comparedwith conventional TiAl alloys.

high temperature strength, compared with conventional TiAl alloys.
Therefore, EB-PBF not only can reproduce complex shapes of turbine blades, but also control the microstructure. Recently, we also
succeeded in prototyping TiAl turbine blades with 20 cm in longand its microstructure control.

▍ Background & Results
In general, 3DP has been used as a tool for shape control. However, the microstructure and mechanical properties of TiAl alloys
can be freely controlled by changing the process conditions of3DP. Furthermore, we also succeeded in establishing a manufacturing process for TiAl turbine blades with 20 cm in long. The simultaneous control of shape and microstructure by 3DP is expected tolead to new trend in the development of new turbine blades.

▍ Significance of the research and Future perspective
TiAl intermetallic compounds has been used as low-pressure
turbine blades of aircraft engines due to their lightweight, highstrength, and excellent oxidation resistance. In general, TiAl turbine
blade is manufactured by a precision investment casting. However,
TiAl is so active that contamination from crucible and oxidation
are big concerns. Metal 3D printing (additive manufacturing) has
attracted much attention since the process can build 3D objects
with arbitrary shape by repeated powder feed-fusion-solidification
cycles. In particular, electron beam powder bed fusion (EB-PBF) isan optimal process for fabrication of TiAl blades, since the process
is mold-free and done in vacuum. Anisotropic Design & Additive
Manufacturing Research Center at Graduate School of Engineering, Osaka University was established in December 2014, and has
been working on the development of EB-PBF process for TiAl turbine blades. As a result, it is possible to control the microstructureof TiAl by changing the process parameters such as beam current
and scanning speed of EB-PBF. For example, at higher beam currents and lower scanning speeds, the microstructure of EB-PBFed
specimens is similar to that fabricated by casting. In contrast, atlower beam currents and higher scanning speeds, the coolingrate is high, so that a “massive transformation” and subsequent
formation of nano-lamellar structure occurs, resulting in excellent

Fig. 1 A schematic drawing of EB-PBF process. It is possible to control internal
shape of 3D products by adding layer-on-layer of material.

Fig. 2 It is possible to control microstructure of TiAl alloys by EB-PBF. A nano-scaled layered microstructure can be obtained through a unique phase transformation. The strength of the alloys with the nano-scaled layered microstructureis 1.7 times higher than that of casting alloys.

P a t e n t Japanese Patent No. 6792837
Cho, Ken; Yasuda, Hiroyuki; Nakano, Takayoshi et al. Peculiar microstructural evolution and tensile properties of β-containing γ-TiAl alloys fabricated byelectron beam melting. Additive Manufacturing. 2021, 46: 102091. doi: 10.1016/j.addma.2021.102091
Tr e a t i s e
Cho, Ken; Yasuda, Hiroyuki; Nakano, Takayoshi et al. Improving the tensile properties of additively manufactured β-Containing TiAl alloys via
microstructure control focusing on cellular precipitation reaction, Crystals, 2021, 11 (7), p.1-13. doi: 10.3390/cryst11070809
http://www.mat.eng.osaka-u.ac.jp/sipk/am/UR
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http://www.mat.eng.osaka-u.ac.jp/msp6/nakano/K e y w o r d 3D printing, additive manufacturing, aerospacematerials, intermetallics, high temperature structural materials