Fig. 5: Effect of cooling condition and common elements in the superalloys on crack susceptibility, and qualitative critical process window of LPBF process for the superalloys.
a Effect of crystal growth rate on the solidification behaviours under rapid solidification conditions of AM. Variations of solute partition coefficient and freezing range coefficient with the Peclet number (Pe) in the Ni–X binary system (X = Mo, Nb, C, Hf and Zr). V and R are the velocity and width of the solid/liquid interface, respectively. D is solute diffusion coefficient in the liquid, and mv is the slope of liquid. b Maps of the operating conditions and the corresponding cracking densities. The subfigure is redrawn from the data in the reference11. El is linear energy density. c Influence of common elements in superalloys on crack susceptibility. The bottom axis and left bars are used to show the segregation range, and the top axis and right bars show the freezing range coefficients of the solute elements. d Qualitive critical process window for the superalloys in AM. The bottom axis is the mass fraction of the grain boundary strengthening elements (bars from the left to the right), including Zr, Hf, B and C, and the top axis is the mass fraction of the main preliminary elements in the γ′ phase (bars from the right to the left), Al, Ta, and Ti, which reflects the volume fraction of γ′ phase. The central bars occupying the remaining space are used to qualitatively estimate the width of the crack-free critical process window in additively manufactured superalloys.
