The cracking behavior of the new Ni-based superalloy GH4151 in the triple melting process

In this paper, the mechanism of crack formation in VIM, ESR, and VAR of GH4151 alloy ingots is discussed. The cracks in VIM ingots are hot tearing, mainly caused by severe segregation of elements such as Nb, Ti, and Al in VIM electrodes, which promotes the precipitation of (y+y') eutectic and Laves phases and thus leads to the formation of hot tearing. On the other hand, cracks in ESR and VAR ingots are cold cracks caused by the uneven distribution of y' phases. The temperature range for the precipitation of (y+y') eutectic phases is 1160 degrees C-1148 degrees C, while that for y' phases is 1137 degrees C-1072 degrees C. At tem-peratures below 884 degrees C, the uneven precipitation of y' phases results in a maximum in-ternal stress of 1096 MPa at room temperature. Based on computational fluid dynamics (CFD) simulations, to avoid large internal stresses caused by the precipitation of y' phase, the ingot should be removed from the water-cooled crystallizer within 57 min. Annealing is an effective measure to improve the quality of electrodes. After annealing treatment, the y' phase in the alloy transforms from short rod-shaped to square-shaped, and the decom-position of Laves phase promotes the precipitation of mu phase and o- phase from the matrix, improving the mechanical properties of the alloy. (c) 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).