Hot ductility behavior of new Ni-based superalloy G27: Influence of solution annealing on the liquation cracking susceptibility

The hot ductility behavior of new Ni-based superalloy G27 was investigated using Gleeble™ 3800 under various standard solution-annealing conditions to study how solution annealing treatments, which result in different grain sizes, affect the alloy's liquation cracking susceptibility. Hot ductility loss is primarily attributable to subsolidus grain boundary (GB) liquation caused by boron (B) segregation. The 1010 °C/1h condition, which produces the finest grain size due to GB pinning by γ′, shows minor B segregation, the shallowest ductility drop, and the narrowest brittle temperature range (BTR). In contrast, the 1110 °C/1h condition, which results in the coarsest grains, exhibits pronounced B segregation, the steepest ductility drop, and the widest BTR. The extent of B segregation is suggested to be influenced by both grain size and the presence of Mo–B-rich precipitates. In the 1010 °C/1h condition, fine-grain size and Mo–B-rich particles—which bind significant amounts of B—minimize B segregation. Substantial B segregation at 1110 °C/1h results from the combined effects of coarse grains and the dissolution of Mo–B-rich precipitates, releasing all bound B atoms into the matrix that subsequently segregate to the GBs. The formation of a thicker intergranular liquid film enriched in B due to increased B segregation is believed to extend the resolidification temperature range during cooling, thereby widening the BTR in G27.