Effect of Carbon Content on Recrystallization of Single Crystal Superalloy

The single crystal superalloy with 0.019% C, 0.048% C, 0.074% C and 0.094% C was cast using screw selecting method in the directionally solidified furnace. These alloys were grit blasted and heat treated at 1 250℃ and 1 300℃ at vacuum atmosphere respectively to investigate the effect of C content on the recrystallization. The results show that with the increase of carbon content, the volume fraction of carbide increases, and its morphologies change from blocky shape to framework-like shape and developed framework-like shape. With the increase of carbon content, the recrystallized layer depth of the alloy has no obvious variation It indicates that the addition of carbon has no suppression effect on the recrystallization in this alloy. With the rise of heat treatment temperature, the recrystallized layer depth dramatically increases. The suppression effect of the C content on recrystallization is related to the morphology and density of carbide formed in the alloy. If high-density carbide forms in the alloy surface layer, it can hold back the recrystallized grain boundaries by pinning effect, and thus inhibit recrystallization.