Abstract
Oxidation resistant fourth and fifth generation Ni base superalloys were developed. The fourth generation superalloys TMS-138A were modified by increasing the content of Al and Cr and deceasing Mo. Designed alloys were cast as single crystal and examined in cyclic and isothermal exposures at 1100°C and creep rupture test. Under high temperature/low stress condition, 0·5 wt-% of Al addition was effective to improve the oxidation resistance but degrade creep property. Cr addition and Mo and W reduction were effective to improve the oxidation resistance and display creep property almost equal to the original TMS-138A. The fourth generation superalloy TMS-138 and fifth generation superalloy TMS-173 were also modified. By adding Cr and removing Mo and W, their oxidation resistances were dramatically improved. Thus it was found that it is possible to improve the oxidation resistance of Ru containing SC superalloys with keeping the high temperature strength by the increase in Cr and decrease in Mo and W.
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