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 εmin 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 + M23C6) 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.