Clean recycling of spent nickel-based single-crystal superalloy by molten magnesium

Nickel -based single -crystal superalloys are designed for extreme conditions due to their superior corrosion and creep resistance properties. However, these pose challenges in the subsequent recycling after reaching their endof -life. Molten magnesium (Mg) can rapidly corrode the stable spent nickel -based superalloys and selectively dissolve nickel (Ni). This waste -free process represents an effective method for recycling spent superalloys and accomplishing metal regeneration. This study investigates the mechanism of selectively dissolving Ni from DD5, a nickel -based single -crystal superalloy, by optimizing process temperature, time, and Mg content in an inert atmosphere. Vacuum distillation was employed to separate the resulting Mg, residual superalloy (i.e., the material left post -extraction), and Ni-rich alloy (i.e., the metal product selectively extracted). The findings revealed that the residual superalloy after selective Ni dissolution is characterized by a porous skeleton structure with pore sizes predominantly ranging from 2 to 30 nm and a low compressive strength which is 1/10 of the original DD5 superalloy.