Experimental and theoretical study of redistribution of alloying elements in Ni-based weld joints at high temperatures

Ni-based diffusion couples were investigated experimentally at 1000 and 1200 °C. The experimental results were compared with theoretical calculations. Equilibrium calculations needed were obtained using CALPHAD approach. The diffusion processes were simulated by means of DICTRA program. The thermodynamic database TCNI was used for equilibrium calculations. User kinetic database was taken for evaluation of diffusion fluxes. The experimental techniques of light microscopy and analytical electron microscopy (TEM, SEM, EDAX) were used. An additional microhardness measurement was also performed. Some particular aspects of the joining of the Ni-based superalloys are discussed. An experimental evidence of validity of local phase equilibrium assumption is given.