Home > Research > Research Centers > Research Center for Structural Materials (RCSM) > High Temperature Materials Design Group

High Temperature Materials Design Group

Novel high-temperature materials, which can be used in the temperature range between 400 and 800 ºC, are necessary in order to improve energy efficiency of combustion system and to reduce carbon-dioxide emission. Those materials need to keep high strength at high temperature, high creep resistance, and excellent oxidation resistance. Our current group is developing novel iron-based and Titanium-based alloys that can be used in the above temperature range. We are also cooperating with other groups in the present unit for the development and understanding of new strengthening mechanism, improvement of oxidation and corrosion resistances, development of suitable coating materials.

Specialized Research Field

All group members join the research project titled “High-temperature materials for a low carbon society” and are assigned to two subthemes.

1. Ferritic heat resistant alloys

"Fig.1 Typical microstructure of Precipitation-Strengthened 15 Cr Ferritic Heat-Resistant Steel.The high-temperature strength was improved drastically through the fine precipitates within ferrite matrix." Image

Fig.1 Typical microstructure of Precipitation-Strengthened 15 Cr Ferritic Heat-Resistant Steel.
The high-temperature strength was improved drastically through the fine precipitates within ferrite matrix.


"Fig.2 Stress dependence of creep rupture life of Precipitation-Strengthened 15 Cr Ferritic Heat-Resistant Steel and the conventional steels.The creep strength of NIMS-original steel after 10,000 hour (as shown by red symbols) is twice that of the conventional heat-resistant steels." Image

Fig.2 Stress dependence of creep rupture life of Precipitation-Strengthened 15 Cr Ferritic Heat-Resistant Steel and the conventional steels.
The creep strength of NIMS-original steel after 10,000 hour (as shown by red symbols) is twice that of the conventional heat-resistant steels.


The conventional ferritic heat-resistant steels are strengthened by the fine lath structure of tempered martensitic microstructure and the precipitation of carbonitrides. However, the strengthening effect of martensitic microstructure decreases during the exposure to high temperature for a long-term because of structural degradation. In the previous NIMS project, in order to improve the high-temperature, long-term stability of the microstructure and strength, we designed "Precipitation-Strengthened 15 Cr Ferritic Heat-Resistant Steel", which microstructure is ferrite matrix with very low dislocation density through solid-solution treatment, and is strengthened by the precipitation of intermetallic compounds (Fig. 1). Furthermore, we succeeded to double the creep-rupture strength of the new steels at 650 ºC (Fig. 2), although the thermal expansion coefficient, formability and cost of the new steels were kept same level as that of the conventional steels.


In the present project, we will investigate the creep strength of the Precipitation Strengthened 15 Cr Ferritic Heat-Resistant Steel at the higher temperature than 700 ºC, and try to solve the new mechanism of high-temperature creep strength. We'll also investigate the steam oxidation resistance and weldability of the steel, and will decide the optimum alloy compositions, heat treatment and microstructure. And we try to propose the new materials design concept for the application to high-temperature large structural components in power plants and so on.


2. High temperature light alloys

"Fig. 3  Development history of Ti alloysOur target is to design high-temperature Ti alloys that can be used above 600ºC" Image

Fig. 3 Development history of Ti alloys
Our target is to design high-temperature Ti alloys that can be used above 600ºC


High-temperature Titanium (Ti) alloys are commonly used in jet engine due to its small specific gravity. The application temperature for commercial aero-engines is limited up to 600 ºC because of drastic deteriorating of strength and heavy oxidation after short time performance. We are now developing novel high-temperature Ti alloys with new strengthening methods by introducing new kinds of precipitates and/or fine particles (oxides, carbides etc.) stabled at high temperature. New coating materials will be developed together with the new alloys that can survive above 600 ºC (Fig. 3).



"Fig. 4  Transformation temperature and output of shape memory alloysWe search new shape memory alloys indicating comparable output in TiNi in the temperature range between 400 and 600 degree C." Image

Fig. 4 Transformation temperature and output of shape memory alloys
We search new shape memory alloys indicating comparable output in TiNi in the temperature range between 400 and 600 degree C.


We are also developing new kinds of high-temperature materials indicating not only high strength at high temperature but also excellent functional properties. We focus high-temperature shape memory alloys that can recover their shapes by detecting temperature after deformation at high temperature. The alloy design of high-temperature shape memory alloys that can work in the temperature range between 400 and 600 ℃ will be established by controlling martensitic transformation (Fig. 4).


Inquiry about this page

Functional Structure Materials Group
1-2-1 Sengen, Tsukuba, Ibaraki, 305-0047 JAPAN
E-Mail: MITARAI.Yoko=nims.go.jp(Please change "=" to "@")
National Institute for Materials Science (NIMS)
1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, JAPAN
TEL.+81-(0)-29-859-2000
FAX.+81-(0)-29-859-2029