Development of a 4th generation DS superalloy

Ni-base directionally solidified (DS) superalloys have the advantage of production costs over the single crystal (SC) superalloys because of better yield rate of casting and a simpler heat treatment compared with SC superalloys. In our previous work, we developed a third generation DS superalloy TMD-103 which exhibits good creep strength, equivalent with second generation SC superalloys. In this study, we attempt to develop a fourth generation DS superalloy that have better creep strength than TMD-103. To strengthen the grain boundaries of the new DS alloys, C and B were added to the fourth generation SC superalloy, TMS-138, that has good phase stability and a long creep life by Ru and Mo addition. Creep behavior of the as-cast and heat-treated new DS alloy is investigated. As a result of creep tests at 1100 degrees centigrade under a load of 137 MPa, the creep time at 1% strain in the heat-treated alloy is twice as long as that of TMD-103.