Development of Next-Generation Ni-Base Single Crystal Superalloys

Abstract

Based on a fourth generation single crystal (SC) superalloy, TMS-138, we designed new SC alloys that contain higher amount of refractory elements, Nb, Ta, Mo, or Re, for strengthening. The Ru content was also increased to improve the phase stability. The creep strength and microstructure of these alloys were examined and compared with those of the base alloy TMS-138 and a third generation SC superalloy, CMSX-10K. As predicted by our alloy design program, TMS-162 (Mo and Ru addition) and TMS-173 (Re and Ru addition) exhibited excellent creep properties. Their times to 1% creep deformation at 1100 C/137MPa were about 2.5 times as long as that of TMS-138 and 5 times as long as that of CMSX-10K. The temperature capability of TMS-162 has reached a project target of 1100 C under stress at 137MPa and a creep rupture life as long as 1000 h, which is the highest ever reported.

Diffusion and γ′ Phase Coarsening Kinetics in Ruthenium Containing Nickel Based Alloys

“…12,13) Intensive researches are being conducted concerning the role of Ru as a new potent alloying element in the next generation of the single crystal nickel based superalloys. [14][15][16][17][18] The interdiffusion of refractory elements in Ni based superalloys is a field of interest since it is important in explaining the beneficial effect of these elements on high temperature processes. Some of the results regarding this topic in Ni based binary and some ternary systems have been reported in literature.…”

Classification and microstructural stability of high generation single crystal Nickel-based superalloys

“…As more dislocations settle at the interface, the mesh spacing gets smaller and will further prevent dislocations from entering and shearing the γ' precipitates [21]. A clear relationship between mean dislocation network spacing at the γ/γ' interfaces and the minimum creep rate was shown in the work of Koizumi et al [22]. As the spacing becomes finer, the creep rate drastically decreases.…”

“…The opposite effect to Mo and Re was observed for Ta and Nb, which tend to bring lattice misfit between γ and γ' phases closer to zero. In consequence, the dislocation network becomes coarser and creep deformation by dislocation cutting is easier to occur [22]. Another element, which improves creep properties, is Co.…”

Creep deformation behaviour of Rhenium free Ni-based single crystal superalloys LSC-15

“…In general, more refractory elements such as rhenium improve the creep resistance of the materials for advanced turbine blade [1][2][3][4]. It has also been reported that the γ /γ rafting behaviour is effective for creep resistance in case of the single crystal (SX) superalloys [5,6]. However, the price of rhenium, which is primarily consumed for the production of nickel base superalloys, has been substantially increasing for several years.…”