Abstract
In advanced industrial gas-turbine systems, there has been a great demand for new single crystal (SC) superalloys with an excellent combination of high-temperature creep strength, hot-corrosion resistance and oxidation resistance. In this study, ten nickel-based SC superalloys were designed with the aid of the d-electrons concept. Their chemical compositions were in the range of 1.2-1.5% Ti, 3.8-6.5% Cr, 11% Co, 0-1.4% Mo, 6.5-7.4% Ta, 5.0-6.0% W, 3.6-5.4% Re, 5.1-5.5% Al, 0.12-0.14% Hf and balanced Ni in mass% units. A series of experiments such as creep rupture tests, burner rig tests and cyclic oxidation tests was conducted with the heat-treated SC specimens of these alloys. All the designed alloys were found to be superior in the creep rupture life to a second generation superalloy, CMSX-4. In the hot-corrosion resistance estimated from the barner rig tests, any designed alloys were comparable or even superior to CMSX-4. The oxidation resistance was very different amount the designed alloys, but some of them showed higher resistance than CMSX-4. Thus the SC alloys containing about 4-5 mass% Re had about 20 K higher temperature capability than CMSX-4, while exhibiting excellent hot-corrosion resistance and oxidation resistance.
