Fig.1 Phase diagram of Ir-Pt-Al at 1500°C
NEDO Industrial Technology |
Development of refractory superalloys for propulsive engine of space plane |
Representative researcher : Yoko Yamabe-Mitarai
Hiroko Aoki (Visiting researcher)
Fig.1 Phase diagram of Ir-Pt-Al at 1500°C |
Fig. 2 Minimum creep rate of Ir-Pt-Al alloys |
A space plane which is a reusable system that produces little air pollution using liquid hydrogen as a propellant is very promising one in order to decrease cost of transport and to protect environment. To develop the space plane, the properties of the propulsive engine need to improve. It is necessary to produce a heat exchanger by high temperature materials. The heat exchanger is generally exposed to high temperature but not subjected to high stress. The material, which has long creep life under low stress at high temperature that fabricability, is great demand. To offer high temperature material for the heat exchanger, we have developed materials based on Ir with high melting temperature. Our target is that development of an alloy with long creep life of more than 160 hours at 1500°C at 100MPa, that offers good ductility at room temperature and good fabricability.
Ir-Pt-Al alloys were investigated because it is expected that solid solution hardening effect by Pt and Al, and precipitation hardening effect by IrAl with B2 structure. The microstructure and creep property of the Ir-Pt-Al alloys were investigated and then the phase diagram was determined experimentally.
The phase diagram is shown in Fig. 1. The fcc+Pt3Al two-phase region was widely existed. On the other hand, the fcc+IrAl two-phase region was narrow. In the fcc+IrAl region, fine precipitates were observed.
The minimum creep rates of the Ir-Pt-Al alloys are shown with those of the Ir-Pt and Ir-Al alloys at 1500°C, 30MPa in Fig. 2. The Ir-Al alloy showed the smallest minimum creep rate and its creep life was over 160 hours. Under this condition, the precipitation hardening of IrAl is effective. However at 100MPa, the creep life was short. Other solid solution elements are under investigation.
Budget in 2001: 8800000yen Original paper : 1 Presentations : 2
Topics : Corroboration work wkth Furuya Co. Ltd..