Research Development of Solidification Characteristics of a Mo-rich Ni₃Al Based Single Crystal Superalloy

As compared with traditional Ni based single crystal (SC) superalloy, the composition characteristic of Mo-rich Ni₃Al based SC superalloy is high Al and Mo contents, which indicate that this alloy has the advantage of low density. This work summarized the solidification characteristics of this alloy. Al was found to significantly increase the average liquid diffusion coefficient during solidification, and the liquid diffusion coefficients of Ni₃Al based SC superalloys were one to two orders of magnitude higher than those of Ni based SC superalloys, reaching 10^-8 m²/s magnitude. Meanwhile, high Al and Mo contents in experimental alloy led to the solidification of interdendritic primary γ' phase and Mo-rich phase at the last stage of solidification, which was significantly different from the typical interdendritic precipitation of Ni based SC superalloy (γ/γ' eutectic and γ' phase). Moreover, the influence of high Al and Mo contents on solidification characteristic temperatures was little. Mo had the strongest tendency to segregate to interdendritic residual liquid phase during solidification of Mo-rich Ni₃Al based SC superalloy, and this microsegregation behavior can decrease the tendency of freckle formation. The investigation of solidification behavior of this Mo-rich Ni₃Al based SC superalloy will be beneficial for the preparation technique and industrial application for this newly developed SC superalloy.