In the components, which are used under
high temperature such as in aircraft engines and industrial gas turbine,
Nickel(Ni)-based heat-resistant superalloys are generally used because of its excellent heat-resistance properties.
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Tohoku University research group headed by
Prof. Kiyohito Ishida,
Graduate School of Engineering, has succeeded in
developing cobalt(Co)-based high temperature alloys having an even higher
strength at high temperatures than the conventional Ni-base super alloys.
The research group has conducted studies
to calculate on the alloy phase diagram, which shows structure and stability of
phase in alloys using computing simulations. |
A typical electron maicrograph taken from
the Co-Al-W superalloy. Cuboid particles strengthen the Co-based alloy at high temperatures. |
In this process, a new intermetallic
compound with a L12 structure, represented by γ' Co3(Al,W), was found in the
alloys composed of cobalt, aluminum and tungsten. Alloys, strengthened by the
compound Ni3Al with the L12 structure, are known as a Ni-based high temperature
heat-resistant materials, where this compound, generally called γ’ phase, shows
a unique mechanical property to harden as the temperature rises.
On the other hand, in conventional
Co-based alloys, no intermetallic compound suitable for strengthening at high
temperatures as well as the NiзA1 has been reported.
This study has contributed to reveal that
the new discovered ternary compound, γ' Co3(Al,W), has the same L12
structure as the NiзA1. Furthermore, it was also confirmed that the Co-Al-W
based alloys with a fine dispersion at the γ' phase show a smaller loss of
strength at high temperatures and can obtain higher temperature strength than
the conventional Ni-base superalloys.
From this, we can imply that it is possible to
apply the Co-based high temperature alloys to aircraft engines and industrial
gas turbine to reduce its effects on environment such as the yield of high
thermal efficiency and the reduction of CO2 emissions.
Research achievements were made by the
following members; Prof. Kiyohito Ishida and Assoc. Prof. Katsunari Oikawa of
School of Engineering, and Prof. Ryosuke Kainuma of
Institute of
Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University.
The findings have been published in the “Science” (April 7, 2006), a major US
science journal.
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Contact:
Prof. Kiyohito Ishida
Graduate School of Engineering,
Tohoku University
Tel: +81-22-795-7321 Fax: +81-22-795-7321
