METHOD FOR MANUFACTURING COBALT-BASED ALLOY STRUCTURE, AND COBALT-BASED ALLOY STRUCTURE OBTAINED THEREBY

1 . A method for manufacturing a cobalt-based alloy structure, the cobalt-based alloy structure comprising a first structure region comprising a hollow space and a second structure region filled in the hollow space,

the method comprising the steps of:

forming the first structure region by additive manufacturing from a first cobalt-based alloy powder having a particle size distribution within a range from 5 to 85 μm and a volumetric basis 90% diameter within a range from 40 to 80 μm; and

forming the second structure region in the hollow space by hot isostatic pressing, the hollow space being filled with a second cobalt-based alloy powder having a particle size distribution within a range from 5 to 85 μm and a volumetric basis 90% diameter within a range from 40 to 80 μm.

2 . The method according to claim 1 ,

wherein the first and the second cobalt-based alloy powder comprising:

0.08 mass % or more and 0.25 mass % or less of carbon;

0.1 mass % or less of boron;

10 mass % or more and 30 mass % or less of chromium;

5 mass % or less of iron, 30 mass % or less of nickel, the total content of the iron and the nickel being 30 mass % or less;

at least one of tungsten and molybdenum, the total content of the tungsten and the molybdenum being 5 mass % or more and 12 mass % or less;

at least one of titanium, zirconium, niobium, tantalum, hafnium and vanadium, the total content of the titanium, the zirconium, the niobium, the tantalum, the hafnium and the vanadium being 0.5 mass % or more and 2 mass % or less;

0.5 mass % or less of silicon;

0.5 mass % or less of manganese;

0.003 mass % or more and 0.1 mass % or less of nitrogen; and

the balance being cobalt and impurities.

3 . The method according to claim 1 , wherein

the method further comprises the step of recycling the first cobalt-based alloy powder, the step of recycling the first cobalt-based alloy powder comprising the substeps of:

collecting the first cobalt-based alloy powder unused in the step of forming the first structure region; and

classifying the first cobalt-based alloy powder collected into the predetermined particle size, and

wherein the second cobalt-based alloy powder comprises the first cobalt-based alloy powder recycled in the step of recycling the first cobalt-based alloy powder.

4 . The method according to claim 2 , wherein

the method further comprises the step of recycling the first cobalt-based alloy powder, the step of recycling the first cobalt-based alloy powder comprising the substeps of:

collecting the first cobalt-based alloy powder unused in the step of forming the first structure region; and

classifying the first cobalt-based alloy powder collected into the predetermined particle size, and

wherein the second cobalt-based alloy powder comprises the first cobalt-based alloy powder recycled in the step of recycling the first cobalt-based alloy powder.

5 . A cobalt-based alloy structure manufactured by the method according to claim 1 , wherein

a predetermined portion of the structure has a 0.2% proof stress at room temperature of 500 MPa or more and a tensile strength at 800° C. of 300 MPa or more.

6 . The cobalt-based alloy structure according to claim 5 , wherein

the structure is a turbine stator blade, and

the portion is an outer ring side end wall.

7 . A cobalt-based alloy structure manufactured by the method according to claim 2 , wherein

a predetermined portion of the structure has a 0.2% proof stress at room temperature of 500 MPa or more and a tensile strength at 800° C. of 300 MPa or more.

8 . The cobalt-based alloy structure according to claim 7 , wherein

the structure is a turbine stator blade, and

the portion is an outer ring side end wall.