Carbide-forming elements are added to nickel-based superalloys so as to minimize grain defects, such as freckle and stray grain defects. More specifically, carbide-forming elements that form from the liquid in the mushy zone of the solidification front of single crystal (SC) and directionally solidified (DS) nickel-based superalloys are added so as to reduce the formation of freckle and stray grain defects in such alloys. A preferred nickel-based superalloy includes, by weight, between about 6.00%-9.25% tantalum, 4.75%-6.50% tungsten, at least about 2.75% rhenium, between about 5.00% to about 7.00% aluminum, at least about 0.10% hafnium and carbon in an amount sufficient (typically between about 0.10-0.15% by weight) to form carbides with other constituents to reduce significantly freckle formation in the mushy zone of the superalloy during casting.