Ni-Based Alloy Softened Powder and Method for Manufacturing Same

Abstract

An objective of the invention is to provide an Ni-based alloy softened powder that is formed of a high precipitation-strengthened Ni-based alloy material, has better forming/molding processability than ever before, and is suitable for powder metallurgy. The Ni-based alloy softened powder has a chemical composition allowing γ′ phase precipitated in γ phase as a matrix to have an equilibrium precipitation amount of 30-80 volume % at 700° C., has an average particle size of 5-500 μm, and includes particles comprising a polycrystalline body of fine crystals of the γ phase. The γ′ phase is precipitated on grain boundaries of the γ phase fine crystals in an amount of 20 volume % or more. And, the particles have a Vickers hardness of 370 Hv or less at room temperature.

1 . An Ni-based alloy softened powder, having a chemical composition allowing γ′ phase precipitated in γ phase as a matrix to have an equilibrium precipitation amount of 30 volume % or more and 80 volume % or less at 700° C., the softened powder having an average particle size of 5 μm or more and 500 μm or less, the softened powder comprising particles comprising a polycrystalline body of fine crystals of the γ phase, the γ′ phase being precipitated on grain boundaries of the fine crystals of the γ phase in an amount of 20 volume % or more, the particles having a Vickers hardness of 370 Hv or less at room temperature. 
     
     
         2 . The Ni-based alloy softened powder according to  claim 1 , wherein
 the chemical composition comprises:   5 mass % or more and 25 mass % or less of Cr;   more than 0 mass % and 30 mass % or less of Co;   1 mass % or more and 8 mass % or less of Al;   the total amount of Ti, Nb and/or Ta being 1 mass % or more and 10 mass % or less;   10 mass % or less of Fe;   10 mass % or less of Mo;   8 mass % or less of W;   0.1 mass % or less of Zr;   0.1 mass % or less of B;   0.2 mass % or less of C;   2 mass % or less of Hf;   5 mass % or less of Re;   0.003 mass % or more and 0.05 mass % or less of O; and   a balance being Ni and inevitable impurities.   
     
     
         3 . The Ni-based alloy softened powder according to  claim 1 , wherein
 the chemical composition is a chemical composition that allows the γ′ phase to have a solvus temperature of 1,100° C. or higher.   
     
     
         4 . The Ni-based alloy softened powder according to  claim 3 , wherein
 the Ni-based alloy softened powder has a chemical composition that allows the γ′ phase to have the equilibrium precipitation amount of 45 volume % or more and 80 volume % or less at 700° C.   
     
     
         5 . The Ni-based alloy softened powder according to  claim 1 , wherein
 the particles have a Vickers hardness of 350 Hv or less at room temperature.   
     
     
         6 . A method for manufacturing an Ni-based alloy softened powder having a chemical composition allowing γ′ phase precipitated in γ phase as a matrix to have an equilibrium precipitation amount of 30 volume % or more and 80 volume % or less at 700° C., the softened powder having an average particle size of 5 μm or more and 500 μm or less, the softened powder comprising particles comprising a polycrystalline body of fine crystals of the γ phase, the particles having a Vickers hardness of 370 Hv or less at room temperature, the method comprising:
 a precursor powder preparation step of preparing a precursor powder that has the chemical composition and comprises particles comprising a polycrystalline body of fine crystals of the γ phase; and 
 a powder softening high temperature and slow cooling heat treatment step of subjecting the precursor powder to a high temperature and slow cooling heat treatment in which the precursor powder is heated to a temperature that is equal to or higher than the solvus temperature of the γ′ phase and lower than the melting point of the γ phase to cause the γ′ phase to enter into solid solution in the γ phase and subsequently cooled slowly from this temperature to a temperature lower than the solvus temperature of the γ′ phase at a cooling rate of 100° C./h or less to produce the Ni-based softened powder in which the γ′ phase is precipitated on grain boundaries of the fine crystals of the γ phase in an amount of 20 volume % or more. 
 
     
     
         7 . A method for manufacturing an Ni-based alloy softened powder having a chemical composition allowing γ′ phase precipitated in γ phase as a matrix to have an equilibrium precipitation amount of 30 volume % or more and 80 volume % or less at 700° C., the softened powder having an average particle size of 5 μm or more and 500 μm or less, the softened powder comprising particles comprising a polycrystalline body of fine crystals of the γ phase, the particles having a Vickers hardness of 370 Hv or less at room temperature, the method comprising:
 a single-phase precursor powder preparation step of preparing a single-phase precursor powder that has the chemical composition and comprises particles comprising a polycrystalline body of single-phase fine crystals of the γ phase; and 
 a powder softening sub-high temperature and slow cooling heat treatment step of subjecting the single-phase precursor powder to a sub-high temperature and slow cooling heat treatment in which the single-phase precursor powder is heated to a temperature that is equal to or higher than a temperature 80° C. lower than the solvus temperature of the γ′ phase and lower than the solvus temperature and cooled slowly from this temperature at a cooling rate of 100° C./h or less to produce the Ni-based softened powder in which the γ′ phase is precipitated on grain boundaries of the single-phase fine crystals of the γ phase in an amount of 20 volume % or more. 
 
     
     
         8 . A method for manufacturing an Ni-based alloy softened powder having a chemical composition allowing γ′ phase precipitated in γ phase as a matrix to have an equilibrium precipitation amount of 30 volume % or more and 80 volume % or less at 700° C., the softened powder having an average particle size of 5 μm or more and 500 μm or less, the softened powder comprising particles comprising a polycrystalline body of fine crystals of the γ phase, the particles having a Vickers hardness of 370 Hv or less at room temperature, the method comprising:
 a single-phase precursor powder preparation step of preparing a single-phase precursor powder that has the chemical composition and comprises particles comprising a polycrystalline body of single-phase fine crystals of the γ phase; and 
 a powder softening high temperature and slow cooling heat treatment step of subjecting the precursor powder to a high temperature and slow cooling heat treatment in which the single-phase precursor powder is heated to a temperature that is equal to or higher than the solvus temperature of the γ′ phase and lower than the melting point of the γ phase and subsequently cooled slowly from this temperature to a temperature lower than the solvus temperature of the γ′ phase at a cooling rate of 100° C./h or less to produce the Ni-based softened powder in which the γ′ phase is precipitated on grain boundaries of the single-phase fine crystals of the γ phase in an amount of 20 volume % or more. 
 
     
     
         9 . The method for manufacturing an Ni-based alloy softened powder according to  claim 6 , wherein
 the chemical composition comprises:   5 mass % or more and 25 mass % or less of Cr;   more than 0 mass % and 30 mass % or less of Co;   1 mass % or more and 8 mass % or less of Al;   the total amount of Ti, Nb and/or Ta being 1 mass % or more and 10 mass % or less;   10 mass % or less of Fe;   10 mass % or less of Mo;   8 mass % or less of W;   0.1 mass % or less of Zr;   0.1 mass % or less of B;   0.2 mass % or less of C;   2 mass % or less of Hf;   5 mass % or less of Re;   0.003 mass % or more and 0.05 mass % or less of O; and   a balance being Ni and inevitable impurities.   
     
     
         10 . The method for manufacturing an Ni-based alloy softened powder according to  claim 6 , wherein
 the precursor powder preparation step comprises an atomization sub-step.   
     
     
         11 . The method for manufacturing an Ni-based alloy softened powder according to  claim 6 , wherein
 the chemical composition is a chemical composition that allows the γ′ phase to have a solvus temperature of 1,100° C. or higher.   
     
     
         12 . The method for manufacturing an Ni-based alloy softened powder according to  claim 11 , wherein
 the Ni-based alloy softened powder has a chemical composition that allows the γ′ phase to have an equilibrium precipitation amount of 45 volume % or more and 80 volume % or less at 700° C.   
     
     
         13 . The method for manufacturing an Ni-based alloy softened powder according to  claim 6 , wherein
 the particles have a Vickers hardness of 350 Hv or less at room temperature.   
     
     
         14 . The method for manufacturing an Ni-based alloy softened powder according to  claim 7 , wherein
 the single-phase precursor powder preparation step comprises an atomization sub-step.   
     
     
         15 . The method for manufacturing an Ni-based alloy softened powder according to  claim 8 , wherein
 the single-phase precursor powder preparation step comprises an atomization sub-step.