Prediction Of Phase Constitutions For 3D Printing Nickel-based Superalloys Based On Thermodynamic Analysis

With the continuous improvement of the thrust-to-weight ratio of modern aero-engines,the drawbacks of mechanically connecting the turbine disk and blade through the tenon and tongue groove are obvious.The preparation of an integral blade-disk can completely solve this problem by laser melting deposition.In the study of an integrated blade-disk by laser melting deposition,one of the key issues to realize effective transformation of microstructures and properties of the turbine disk and blade material is to design composition path for gradient materials with excellent performance.In this paper,CALPHAD(Calculation of Phase Diagrams)method was applied.The rapid solidified microstructures of turbine disk GH4169 and turbine blade DZ417G Ni-based superalloys were studied by using Ni-based alloys thermodynamic database,and the method of predicting phase constitutions for laser melting deposition Ni-based alloys was established.On this basis,phase constitutions,phase compositions and phase fractions of five GH4169/DZ417G gradient alloys after laser melting deposition were predicted by thermodynamic analysis.The main research results are as following:(1)CALPHAD method and Ni-based superalloy thermodynamic database were used to analyze the important binary and ternary phase diagrams of Ni-based superalloys,and those phase diagrams were compared with experimental data,the rationality of thermodynamic parameters was confirmed.Ni-X(Al,Ti,Nb,Fe),Fe-Nb,C-Nb binary systems and Ni-AI-X(Co,Cr),Ni-Cr-X(Co,Fe),Ni-C-X(Nb,Ti),Ni-Fe-Nb ternary systems were thoroughly analyzed,which laid the foundation for the solidification transformations analysis of multi-component nickel-based superalloys.(2)The equilibrium cooling processes of turbine disk GH4169 and turbine blade DZ417G nickel-based superalloys were thermodynamically calculated and analyzed.On this basis,phase compositions and phase transformations of rapidly solidified GH4169 and DZ417G alloys were thermodynamically analyzed and predicted by the Scheil model,and were compared with the laser melting deposited microstructures 哦of GH4169 alloy observed by experiments.The results show that the phase constitutions,phase compositions and phase fractions of in the laser-melted Ni-base superalloys can be reasonably predicted.Therefore,the method to predict the phase constitutions of laser melting deposited nickel-based alloys was established based on thermodynamic analysis.(3)Five different mass fractions of GH4169/DZ417G gradient alloys were designed.The phase constitutions,phase compositions and phase fractions of these alloys after laser melting were predicted by thermodynamic analysis.The matrix phase compositions and strengthening phases of each gradient nickel-based alloys can be effectively transformed,meanwhile brittle phases don’t obviously form in those nickel-based superalloys.The study results are beneficial for the design of turbine disk and blade gradient alloys with excellent performance.