A comparative evaluation of hot cracking susceptibility of new Ni-based superalloy G27 and Alloy 718
Achmad Ariaseta, Joel Andersson, Olanrewaju Ojo
Abstract
The hot cracking susceptibility of G27, a new superalloy designed for superior mechanical performance relative to Alloy 718, is compared to that of Alloy 718 by Varestraint testing. G27 is found to be more prone to solidification cracking than Alloy 718. Thermodynamic calculations show that G27 has a wider solidification temperature range (STR) and a higher crack susceptibility index (CSI) based on the steepest slope of the temperature vs. square root of the fraction solid (f s ) curve at f s = 0.98. The higher B and Zr contents in G27, compared to Alloy 718, are likely to be the primary factor contributing to the higher cracking susceptibility, as these elements and their interactions show the strongest influence on the calculated STR and CSI compared to the other elements based on the Scheil simulation. Regarding heat-affected zone (HAZ) liquation cracking, G27 also shows greater susceptibility, likely due to its larger resolidification temperature range of HAZ intergranular liquid and a lower fraction of special boundaries compared to Alloy 718. Although G27 is more prone to hot cracking than Alloy 718, the difference in cracking response between the two is relatively modest, making G27 a promising alternative to Alloy 718 due to its superior mechanical properties. • The hot cracking susceptibility of G27 is compared to that of Alloy 718. • G27 is found to be more prone to solidification cracking than Alloy 718. • Regarding liquation cracking, G27 also shows a greater susceptibility. • The difference in the hot cracking susceptibility of the two alloys is discussed.