Tailoring the creep properties of second-generation Ni-based single crystal superalloys by composition optimization of Mo, W and Ti

摘要

With the aim of further improvement of the high temperature creep resistance performance of Ni-based super-alloys, the composition optimization of Mo, W and Ti elements in second-generation Ni-based single crystal superalloys was conducted by combined thermodynamic calculations and orthogonal experiment approach. The relative content of γ' and topologically close-packed (TCP) phase and solvus temperature of γ' phase were predicated by using Thermo-Calc software and TTNI8 database. Orthogonal experiments involving nine single crystal superalloys were carried out on the size and shape of γ' precipitates, eutectic and TCP phases of heat-treated alloys, and the creep strain and creep lives of these superalloys under the condition of 1030°C and 230 MPa. From Larson-Miller curve, it has been confirmed that some alloys exhibit superior creep performance to Rene N5 alloy. Based on the above results, the influence of alloying elements on the phase composition has been discussed. And the quantitative relations have been established between the creep lives and the solid solution strengthening index, volume fraction of γ' precipitates and TCP phases. Eventually, an appropriate composition range of Mo, W and Ti elements has been confined, and Ni-based single crystal superalloys with superb creep resistance performance have been developed.