Metallurgical Research Laboratory, Yasugi Works, Hitachi Metals Ltd.
In order to improve oxidation resistance and creep-rupture strength of SC-83, a single crystal superalloy for gas-turbine blades, which has been developed by an alloy-designing method and possesses much higher temperature capability than conventional single crystal alloys, the effects of the addition of Hf and Co and the increase of "Solubility Index" were investigated.
The optimum solubility index value was 1.5 and the addition of small amounts of Hf and Co increased oxidation resistance greatly and creep rupture strength slightly.
The finally developed alloy SC-83K which contains 0.1% Hf and 1% Co has much higher creep rupture strength than conventional alloys as well as good structural stability and oxidation resistance.