Effect of returned materials addition ratio on precipitation behavior of inclusions in superalloy
In order to realize the pure smelting of superalloy with high return ratio,the effects of different addition ratios of returned materials on the evolution of inclusions in superalloy smelting process were studied,and the pre-cipitation behavior and formation mechanism of inclusions were discussed in combination with thermodynamic calcu-lations.The results show that the addition of returned material has no obvious effect on the types of inclusions in su-peralloys,but has a great influence on the number and size distribution of inclusions.As the returned material ratio increases from 0％to 60％,the number density of inclusions increases from 19.30 pieces/mm2 to 30.74 pieces/mm2.Among them,the number of carbonitride composite inclusions with oxide as the core increases from 4.47 pieces/mm2 to 10.11 pieces/mm2,and the proportion of large size(particle size greater than 5 μm)inclusions increases from 8.7％to 13.9％.Thermodynamic calculation results show that the theoretical nucleation radius of MgO·Al2O3 in-clusions decreases with the increase of oxygen activity in the melt,and the lattice mismatch between MgO·Al2O3 inclusions and TiN inclusions is low.Compared with the new material,the addition of returned material brings more impurity elements,which leads to a significant increase in the nucleation rate of MgO·Al2O3 inclusions and pro-motes the non-uniform nucleation of TiN and Ti(C,N)inclusions.The calculation results of nucleation kinetics show that with the increase of returned material proportion,the concentration of nitrogen in the system increases,TiN inclusions precipitate earlier,and the size of precipitation also increases gradually.The research results can provide necessary theoretical basis and data support for low-cost production and purification smelting of superal-loys.
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