Effects of Hf and carbides formation behavior on the weld solidification cracking susceptibility of 247LC superalloy.

This study quantitatively and fundamentally evaluated the effects of B and Hf on weld solidification cracking susceptibility for 247LC superalloy, and the behavior was compared with that of 247LC's original composition. To this end, the transverse-Varestraint test was performed by measuring the cracking temperature during weld solidification. The solidification brittle temperature range (BTR) values of the Boron (B)- and Hafnium (Hf)-free 247LC alloys were 206 and 172 K, respectively, which were significantly lower than that of the original 247LC alloy (400 K). Contrastingly, the minimum strain for solidification cracking ε min was similar in both alloys. The metallurgical mechanism for the largely reduced BTR (from 400 K to 172 K) was elucidated especially for the Hf-free 247LC alloy, which was highly dependent on its weld mushy zone range (170 K) calculated by non-equilibrium weld solidification. It was attributed to the suppression of carbide (MC + M 23 C 6) formation for Hf-free 247LC (area fraction: 0.15%) as compared with that of 247LC (area fraction: 4.72%) by direct identifying the solidification cracking surfaces. • Solidification cracking susceptibilities of 247LC and Hf,B-free alloys studied. • Brittle temperature range (BTR) reduced from 400 K to 170 K by nonaddition of Hf. • The reduced BTR attributed to suppressed carbide formation. [ABSTRACT FROM AUTHOR]