Experimental Investigation On The Phase Equilibriums Of Partial Ta/Ru-containing Ternary Alloys In Ni-based Superalloys

Ni-based superalloys are widely applied in aerospace industry due to their excellent mechanical properties at elevated temperature.With the development of aerospace technology,material researchers need to improve the properties of Ni-based superalloys.Recent results show that alloying can significantly improve the comprehensive properties of Ni-based superalloys.Proper additions of Ta,Ru,Mo,Nb,Ti and other elements can enhance the solid solution strengthening effect and have a beneficial impact on the oxidation resistance,corrosion resistance and creep resistance of the alloys.However,excessive addition can easily lead to the formation of TCP phase,which seriously deteriorates the properties and service life of the alloys.Therefore,it is necessary for design of Ni-based superalloys to systematically investigate the phase relationship of Ta/Ru-containing ternary Ni-based alloys.In this study,ten isothermal sections of the Ni-Ta-X(X:V,Ti,Cr)and Ni-Ru-X(X:Mo,Nb)ternary systems were experimentally determined using electron probe microanalysis,X-ray diffraction analysis and differential scanning calorimeter by lmeans of alloying method.The main results were as follows:(1)Two full-composition isothermal sections of the Ni-Ta-V ternary system at 1000? and 1200? were established.The corresponding results indicated that C14(V2Ta)phase had a large solid solubility in both two isothermal sections,and the Ni addition stabilized the C14 phase at 1000?.Besides,the addition of Ta decreased the melting point of the Ni-V alloys.No ternary compound was found in this system.(2)The full-composition phase diagrams of the Ni-Ta-Ti ternary system at 1000 ? and 1200 ? were determined.The results showed that a ternary compound ?phase with small solid solubility existed at both two termperaturcs of this system.(3)Two full-composition isothermal sections of the Ni-Ta-Cr ternary system at 1200? and 1300 ? were experimentally determined.The results showed that the(Ni,Cr)2Ta(HT)phase with C14 structure had a large compositions,which was stabilized by the Ni addition at low temperature.Furthermore,the addition of Ta in Ni-Cr alloys reduced the melting point of the alloys.No ternary compound was found in this system.(4)Two full-composition isothermal sections of the Ni-Ru-Mo ternary system at 1000 ? and 1200 ? were experimentally determined.The results showed that the ?phase and solid solution(Ru)with hep structure had large solid solubility.Additionally,the a phase was stabilized by the Ni addition at 1000?.The phase diagrams of Ni-rich side of the Ni-Ru-Nb ternary system at 1000? and 1200 ?were established.The Ni3Nb and solid solution(Ru)had large solid solubility in this system.