Abstract: A Ni-base superalloy of the present invention essentially includes, by weight %, Co: 9 to 11%, Cr: 9 to 12%, Mo: up to 1%, W: 6 to 9%, Al: 4 to 5%, Ti: 4 to 5%, Nb: up to 1%, Ta: up to 3%, Hf: 0.5 to 2.5%, Re: up to 3%, C: 0.05 to 0.15%, B: 0.005 to 0.015%, Zr: up to 0.05%, and the balance of Ni and inevitable impurities. This alloy, as a component material of an industrial gas turbine, has an excellent resistance to corrosion at high temperatures to deal with low-quality fuel and a resistance to oxidation at high temperatures and high-temperature strength to deal with improvement in thermal efficiency due to high-temperature demands and can ensure a high yield at a casting process.

Abstract: A Ni-base superalloy of the present invention essentially includes, by weight %, Co: 9 to 11%, Cr: 9 to 12%, Mo: up to 1%, W: 6 to 9%, Al: 4 to 5%, Ti: 4 to 5%, Nb: up to 1%, Ta: up to 3%, Hf: 0.5 to 2.5%, Re: up to 3%, C: 0.05 to 0.15%, B: 0.005 to 0.015%, Zr: up to 0.05%, and the balance of Ni and inevitable impurities. This alloy, as a component material of an industrial gas turbine, has an excellent resistance to corrosion at high temperatures to deal with low-quality fuel and a resistance to oxidation at high temperatures and high-temperature strength to deal with improvement in thermal efficiency due to high-temperature demands and can ensure a high yield at a casting process.

Abstract: A Ni-base directionally solidified alloy casting is produced by casting a Ni-base directionally solidified alloy having a composition of 10 to 14 wt. % Co, 2 to 3 wt. % Cr, 1.5 to 2.5 wt. % Mo, 5 to 6.5 wt. % W, 5.7 to 6.5 wt. % Al, 5.5 to 6.5 wt. % Ta, 4.5 to 5.0 wt. % Rd, 0.01 to 1.5 wt. % Hf, 0.01 to 0.30 wt. % C, 0.01 to 0.03 wt. % B, and the balance of Ni and inevitable impurities. The Ni-base directionally solidified alloy casting is subjected to a solid solution treatment process at a temperature in the range of 1250 to 1300° C. Then the Ni-base directionally solidified alloy casting is subjected to a two-stage aging process for aging the Ni-base directionally solidified alloy casting at a temperature in the range of 750 to 1200° C.