Dealloying Superalloy by Liquid Mg for the Selective Extraction of Ni

Liquid Mg is capable of quickly eroding the refractory Ni-based superalloy and selectively dissolve Ni, which opens up a new avenue for the recycling of superalloy scraps for comprehensive metal reclamation. This study aims at investigating the underlining mechanism and kinetics of the selective dissolution of Ni from Inconel 718 (one type of Ni-based superalloy) with liquid Mg, by experimenting at 750, 800, and 850 degrees C for various amounts of time in an inert atmosphere. This selective dissolution process is also known as liquid metal dealloying. Results show that a permeable dealloyed layer was formed resulting from the preferential dissolution of Ni over other metallic elements (e.g., Fe, Cr, Nb, Mo, and Ti). At the dealloying forefront, the grain boundaries of the matrix gamma phase were preferentially eroded by liquid Mg. The opposite concentration gradients of Ni (4-9 wt%) and Mg (12-18 wt%) cross the dealloyed layer suggested their counter diffusion. A higher heating temperature substantially increased the dealloying rate.

Automated summary

Liquid Mg can quickly erode refractory Ni-based superalloys, selectively dissolve Ni, and open up a new pathway for comprehensive metal reclamation of superalloy scraps. Higher heating temperatures substantially increase the dealloying rate, as shown by the experimental results.