発電ガスタービン動翼用Ni基単結晶超合金の開発

摘要

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 percent Ti, 3.8-6.5 percent Cr, 11 percent Co, 0- 1.4 percent Mo, 6.5-7.4 percent Ta, 5.0-6.0 percent W, 3.6-5.4 percent Re, 5.1-5.5 percent Al, 0.12-0.14 percent Hf and balanced Ni in mass percent 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 percent Re had about 20 K higher temperature capability than CMSX-4, while exhibiting excellent hot-corrosion resistance and oxidation resistance.