Nickel-base alloy for gas turbine applications
View Patent ↗A nickel-based alloy suitable for casting gas turbine components having a lower density and basic heat treating process while achieving improved strength is disclosed. Multiple embodiments of the alloy are disclosed capable of providing both directionally-solidified and equiaxed castings. Also disclosed is a method of making a cast and heat treated article utilizing the improved nickel-base alloy.
1. A turbine blade casting from nickel-based alloy having a density about 0.30 pounds per cubic inch, suitable for casting lower longitudinally-stressed gas turbine components, the nickel-based alloy comprising the following composition by weight percent:
Aluminum 3.35-3.65
Titanium 5.01-5.15
Tantalum 2.30-2.70
Chromium 12.01-12.5
Cobalt 11.50-12.50
Iron 0.01-0.15
Copper 0.01-0.10
Tungsten 3.3-3.7
Molybdenum 1.70-2.10
Carbon 0.04-0.12
Boron 0.010-0.020
Zirconium 0.01-20 parts per million
Hafnium 0.0-0.05
Sulfur 0.0001-0.0012
Nitrogen 0.1-25 parts per million
Oxygen 0.1-10 parts per million, and
the remainder Nickel and incidental impurities;
wherein the nickel-based alloy measures an ultimate tensile strength increase at the upper end of an operating spectrum of the turbine blade, greater than approximately 1200 degrees F. in both directionally solidified and equiaxed forms.
2. The nickel based alloy of claim 1 , wherein the nickel-based alloy is solution heat treated following a process comprising:
elevating said alloy to 2050 deg. F.+/−25 deg. F. and holding for 2 hours +/−15 minutes;
cooling said alloy by gas quench to 1100 deg. F. or below;
elevating said alloy to 1975 deg. F.+/−25 deg. F. and holding for 4 hours +/−15 minutes;
cooling said alloy by gas quench to 1100 deg. F. or below;
elevating said alloy to 1550 deg. F.+/−25 deg. F. and holding for 24 hours +/−30 minutes; and,
cooling said alloy to 1100 deg. F. or below.
3. The nickel-based alloy of claim 2 , wherein a thermal barrier coating is applied to the alloy prior to the steps of elevating said alloy to 1975 deg. F.+/−25 deg. F. and holding for 4 hours+/−15 minutes, cooling said alloy by gas quench to below 1100 deg. F., elevating said alloy to 1550 deg. F.+/−25 deg. F. and holding for 24 hours+/−30 minutes, and cooling said alloy to below 1100 deg. F.
4. The nickel-based alloy of claim 2 , wherein said gas for said cooling is selected from the group comprising Argon, Helium, and Hydrogen.
5. The nickel-based alloy of claim 1 , wherein the nickel based alloy comprises:
Aluminum 3.54 -3.56
Titanium 5.08-5.1
Tantalum 2.5
Chromium 12.1-12.2
Cobalt 12.1 -12.2
Tungsten 3.5
Molybdenum 1.9,
wherein a metallurgical stability factor of said alloy is expressed by the formula
N
V
3
=
∑
i
=
1
n
m
i
(
N
V
)
I
where N V3 is between 2.390 and 2.400.
6. A lower longitudinally-stressed gas turbine component nickel-based alloy casting having a density of about 0.30 pounds per cubic inch, the nickel-based alloy comprising the following composition by weight percent:
Aluminum 3.31-3.57
Titanium 4.02-4.98
Tantalum 2.59-3.05
Chromium 11.93-11.97
Cobalt 11.96-12.04
Iron 0.01-0.15
Copper 0.01-0.10
Tungsten 3.08-3.65
Molybdenum 1.44-1.98
Carbon 0.066-0.072
Boron 0.010-0.012
Zirconium 0.1-10 parts per million
Hafnium 0.0-0.05
Sulfur 0.0001-0.0012
Nitrogen 0.01-19 parts per million
Oxygen 0.1-9 parts per million and,
the remainder Nickel and incidental impurities wherein a metallurgical stability factor of the nickel-based alloy is expressed by a formula
N
V
3
=
∑
i
=
1
n
m
i
(
N
V
)
I
where N V3 of the casting is greater than or equal to 2.20 and less than or equal to 2.280 and wherein the tensile strength at 800 degrees F. is greater than or equal to 177 and less than or equal to 180.
7. A lower longitudinally-stressed gas turbine component nickel-based alloy casting having a density of about 0.30 pounds per cubic inch, the nickel-based alloy comprising the following composition by weight:
Aluminum 3.30-3.82
Titanium 5.1
Tantalum 2.4-3.0
Chromium 12.1
Cobalt 11.9-12
Iron 0.01-0.15
Copper 0.01-0.10
Tungsten 3.3-3.5
Molybdenum 1.5-2.0
Carbon about 0.04-0.12
Boron 0.010-0.020
Zirconium 0.1-20 parts per million
Hafnium 0.01-0.05
Sulfur 0.0001-0.0012
Nitrogen 0.1-25 parts per million
Oxygen 0.1-10 parts per million, and
the remainder Nickel and incidental impurities,
wherein the nickel-based alloy has a solution heat treatment window of at least 150 deg. F. in which a majority of a gamma prime strengthening phase dissolves, and
wherein a metallurgical stability factor of the nickel-based alloy is expressed by a formula
N
V
3
=
∑
i
=
1
n
m
i
(
N
V
)
I
where N V3 of the casting is about 2.31.