Ni based superalloy, member of Ni based superalloy, and method for producing same
To provide a manufacturing process of a Ni based superalloy and a member of the Ni based superalloy which achieves both of excellent workability in a manufacturing step of the Ni based superalloy of the precipitation strengthening type which contains much amount of the gamma prime phase and excellent high temperature strength of the Ni based superalloy. The manufacturing process of a Ni based superalloy includes a step for softening the Ni based superalloy and improving the workability, in which the step for softening the Ni based superalloy and improving the workability is a step for precipitating the gamma prime phase that is incoherent with a gamma phase that is a matrix by 20 vol % or more.
1. A manufacturing process of a Ni based superalloy softening material comprising:
a step for preparing a raw material of a Ni-based superalloy, the raw material of a Ni-based superalloy being subjected to a softening step in a next step;
a step for softening the raw material of the Ni based superalloy and improving workability, the step being performed subsequently to the step for preparing a raw material of a Ni-based superalloy, wherein
the step for softening the Ni based superalloy and improving workability is a step for precipitating a gamma prime phase that is incoherent with a gamma phase that is a matrix of the Ni based superalloy by 20 vol % or more, and the step of softening the Ni based superalloy and improving workability comprises:
a first step for hot-forging the Ni based superalloy at a temperature below the solvus of the gamma prime phase; and
a second step, being performed subsequently to the first step, for precipitating the gamma prime phase that is incoherent with a gamma phase that is a matrix by 20 vol % or more by slow cooling at equal to or more than 10° C./h and equal to or less than 100° C./h from a temperature below the solvus of the gamma prime phase and increasing the amount of the gamma prime incoherent phase,
wherein the solvus of the gamma prime phase is 1,050° C. or above; and further comprising a step of cooling the Ni based superalloy by quenching after the second step.
2. The manufacturing process of a Ni based superalloy softening material according to claim 1 , wherein
vickers hardness at the room temperature of the Ni based superalloy softening material after the step for softening the Ni based superalloy and improving workability is 400 or less, and 0.2% proof stress at 900° C. is 300 MPa or less.
3. The manufacturing process of a Ni based superalloy softening material according to claim 1 , wherein
the temperature of starting slow cooling of the second step is a forging temperature of hot forging in the first step and equal to or below the solvus of the gamma prime phase.
4. The manufacturing process of a Ni based superalloy softening material according to claim 1 , wherein
the composition of the Ni based superalloy contains, in mass %, 10% or more and 25% or less of Cr, 30% or less of Co, 3% or more and 9% or less of the total of Ti, Nb and Ta, 1% or more and 6% or less of Al, 10% or less of Fe, 10% or less of Mo, 8% or less of W, 0.03% or less of B, 0.1% or less of C, 0.08% or less of Zr, 2.0% or less of Hf, and 5.0% or less of Re, with the balance including Ni and inevitable impurities.
5. The manufacturing process of a Ni based superalloy softening material according to claim 1 , further comprising a step of cooling the Ni based superalloy to the room temperature by quenching after the second step.