Experimental Measurement Of Interdiffusivities And Calculation Of Diffusion Kinetics In Some Fcc(Co,Ni)-based Alloys Systems

(Co,Ni)-based superalloys are widely used in the aerospace industry due to their excellent high temperature corrosion resistance and thermal stability.With the increasing demand for aero-engine performance in the defense and civil aerospace industries,the design and development of high-performance Co-based and Ni-based superalloys are of great significance for improving the level of China's aerospace industry.Kinetic mobility database is the basis of superalloy material design and process optimization.Based on diffusion kinetic data,combined with various calculation methods,the microstructure evolution and diffusion-related processes can be simulated to accelerate the efficiency of component screening and process optimization of(Co,Ni)-based superalloy material.Up to now,the kinetic mobility database of(Co,Ni)-based superalloys is still not perfect,and many ternary systems containing important additive elements have not been studied.Therefore,the present study is aimed at assessment of the atomic mobilities in Co-Mo-Cr,Co-Mo-V,Ni-Cr-W,Ni-Al-Nb and Ni-Al-Mo five ternary systems.Based on the thermodynamic information and kinetic parameters of each sub-binary systems,the atomic mobilities were optimized by using the experimental method of diffusion couple combined with DICTRA software.The brief achievements of the present work are as follows:(1)According to the thermodynamic phase diagram characteristics of five ternary systems of Co-Mo-Cr,Co-Mo-V,Ni-Cr-W,Ni-Al-Nb and Ni-Al-Mo,the alloy compositions were selected in the fcc single-phase regions and a series of diffusion couples were prepared.The concentration-distance curves of the diffusion couples were determined by EPMA,and the experimental values of the interdiffusion coefficients of the above five systems were calculated using the Whittle and Green method.(2)Combining with the published thermodynamic information of five ternary systems,eight binary systems' atomic mobility parameteis of Co-Cr,Co-Mo,Co-V,Ni-Cr,Ni-W,Ni-Al,Ni-Nb and Ni-Mo in fcc single phase,and the experimental values of the interdiffusion coefficients obtained in this study,the atomic mobility parameters in the above five ternary systems were assessed using the DICTRA software.(3)Based on the atomic mobility parameters evaluated in this study,the interdiffusion coefficients of the five ternary systems,the concentration-distance curves and the diffusion paths of the diffusion couples were calculated and compared with the experimental values.The calculated results agreed well with the experimental data.The error was within the acceptable range,indicating that the atomic mobility parameters obtained in this study were reliable.Based on the present database,it is possible to carry out related kinetic calculations and predictions for the two types of superalloys.