Alloys or metallic compositions – Nickel base – Chromium containing
Reexamination Certificate
2001-08-30
2004-01-06
King, Roy (Department: 1742)
Alloys or metallic compositions
Nickel base
Chromium containing
C420S443000, C148S428000
Reexamination Certificate
active
06673308
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a nickel-base single-crystal superalloy applied to high temperature parts (heat resisting parts) of an industrial gas turbine, such as turbine blades and vanes, a method of manufacturing such superalloy, and gas turbine high temperature parts made of such a superalloy or manufactured in accordance with such method.
With a trend towards high efficiency of a gas turbine, combustion temperature therein rises, so that material for turbine rotor and stator blades has changed from a type of conventional cast alloy to a type of directionally solidified alloy, in which a crystal grain boundary along a stress axial direction is removed to improve creep strength at high temperatures and further to a type of single-crystal alloy, in which grain boundary strengthening elements, the presence of which is a cause for decreasing heat treatment window, are excluded by allowing the crystal grain boundary itself to disappear, so that an optimum heat treatment is applied to increase a volume fraction of gamma prime phase, whereby the creep strength at the high temperatures are further improved.
Development of the single-crystal alloy has switched from the first generation single-crystal superalloy to the second and third generation single-crystal superalloys, aiming at a still further improvement in the creep strength.
The first generation single-crystal superalloy contains no rhenium. Examples of such an alloy include “CMSX-2” disclosed in Japanese Laid-Open Patent Publication No. SHO 59-19032, “Rene′N4” disclosed in U.S. Pat. No. 5,399,313, “PWA-1480” disclosed in Japanese Laid-Open Patent Publication No. SHO 53-146223, and the like.
Stress rupture temperature of the second generation single-crystal superalloys contain about 3% of rhenium is increased by about 30° C. in comparison with that of the first generation single-crystal superalloys. Examples of such an alloy include “CMSX-4” disclosed in U.S. Pat. No. 4,643,782, “PWA-1484” disclosed in U.S. Pat. No. 4,719,080, “Rene′N5” disclosed in Japanese Patent Laid-Open Publication No. HEI 5-59474, and the like.
The third generation single-crystal superalloy contains about 5% to 6% of rhenium. Examples of such an alloy include “CMSX-10” disclosed in Japanese Patent Laid-Open Publication No. HEI 7-138683, and the like.
These single-crystal alloys have been remarkably developed mainly in a field of aircraft jet engines and small gas turbines. It has been intended to convert such technology into a field of large-sized gas turbines for industrial use because of achieving high temperatures directing to improvements in combustion efficiency.
The large-sized gas turbine for industrial use takes longer time for design life as compared with aircraft jet engine or small gas turbine. Accordingly, blade materials require characteristic properties to inhibit formation of TCP (Topologically Close-Packed phase), which serves as a deteriorating phase when used, i.e., a good structural stability.
In the third generation single-crystal superalloy, addition of rhenium in an amount of 5% to 6% makes it possible to increase creep strength in comparison with the second generation single-crystal superalloy. However, the TCP phase, which may serve as a initiation site of creep and low-cycle fatigue failure, tends to occur after using a long period of service time. In the light of such problems, it is therefore hard to apply the third generation single-crystal superalloy to material for the large-sized gas turbine. In view of increase in firing temperature, there has however been demanded material having further higher creep strength.
SUMMARY OF THE INVENTION
An object of the present invention is to substantially eliminate defects or drawbacks encountered in the prior art mentioned above and to provide a nickel-base single-crystal superalloy improved in creep strength and microstructural stability under a high temperature condition, a method of manufacturing such a superalloy and gas turbine high temperature (heat resisting) parts made thereof.
After studies of components of elements contained in a superalloy and amounts thereof, the inventors of the subject application had a finding that there can be obtained a single-crystal alloy, which has at least the same creep strength as that of a single-crystal alloy of the second generation at a temperature of up to 900° C. and under a stress of at least 200 MPa, and on the one hand, the creep strength larger than that of the above-mentioned single-crystal alloy of the second generation at a temperature of at least 900° C. and under a stress of up to 200 MPa, in addition to an excellent structural stability, a method for manufacturing such a specific superalloy and a high temperature (hest resisting) gas turbine part made thereof.
That is, the above and other objects can be achieved according to the present invention by providing, in one aspect, a nickel-base single-crystal superalloy, essentially consisting of, in percentages by weight, 4.0% to 11.0% of cobalt, 3.5% to less than 5.0% of chromium, 0.5% to 3.0% of molybdenum, 7.0% to 10.0% of tungsten, 4.5% to 6.0% of aluminum, 0.1% to 2.0% of titanium, 5.0% to 8.0% of tantalum, 1.0% to 3.0% of rhenium, 0.01% to 0.5% of hafnium, 0.01% to 0.1% of silicon, and a balance being nickel and inevitable impurity, a total amount of rhenium and chromium being not less than 4.0% and a total amount of rhenium, molybdenum, tungsten and chromium being not more than 18.0%.
Further, it is to be noted that an expression such as “4.0% to 11.0% of cobalt” in the present specification equivalently means “cobalt of not less than 4.0% and not more than 11.0%”, and this is to be applied throughout the present specification.
In another aspect, there is provided a nickel-base single-crystal superalloy, essentially consisting of, in percentages by weight, 5.0% to 10.0% of cobalt, 4.0% to less than 5.0% of chromium, 1.0% to 2.5% of molybdenum, 8.0% to 9.0% of tungsten, 5.0% to 5.5% of aluminum, 0.1% to 1.0% of titanium, 6.0% to 7.0% of tantalum, 2.0% to 3.0% of rhenium, 0.01% to 0.5% of hafnium, 0.01% to 0.1% of silicon, and a balance being nickel and inevitable impurity, a total amount of rhenium and chromium being not less than 4.0% and a total amount of rhenium, molybdenum, tungsten and chromium being not more than 18.0%.
In a further aspect, there is also provided a nickel-base single-crystal superalloy, essentially consisting of, in percentages by weight, 5.0% to 10.0% of cobalt, 4.0% to less than 5.0% of chromium, 1.0% to 2.5% of molybdenum, 8.0% to 9.0% of tungsten, 5.0% to 5.5% of aluminum, 0.8% to 1.5% of titanium, 5.0% to less than 6.0% of tantalum, 2.0% to 3.0% of rhenium, 0.01% to 0.5% of hafnium, 0.01% to 0.1% of silicon, and a balance being nickel and inevitable impurity, a total amount of rhenium and chromium being not less than 4.0% and a total amount of rhenium, molybdenum, tungsten and chromium being not more than 18.0%.
In a still further aspect, there is also provided a nickel-base single-crystal superalloy, essentially consisting of, in percentages by weight, all of elements listed in a following group A, at least one of elements selected from a following group B and a balance being nickel and inevitable impurity:
A: 4.0% to 11.0% of cobalt, 3.5% to less than 5.0% of chromium, 0.5% to 3.0% of molybdenum, 7.0% to 10.0% of tungsten, 4.5% to 6.0% of aluminum, 0.1% to 2.0% of titanium, 5.0% to 8.0% of tantalum, 1.0% to 3.0% of rhenium, 0.01% to 0.5% of hafnium, and 0.01% to 0.1% silicon,
B: less than 2% of niobium, less than 1% of vanadium, less than 2% of ruthenium, less than 1% of carbon, less than 0.05% of boron, less than 0.1% of zirconium, less than 0.1% of yttrium, less than 0.1 of lanthanum, and less than 0.1% of cerium.
In a still further aspect, there is also provided a nickel-base single-crystal superalloy, essentially consisting of, in percentages by weight, all of elements listed in a following group C, at least one of elements selected from a following group D and a balance being nickel and inevitable im
Harada Hiroshi
Hino Takehisa
Ishiwata Yutaka
Kobayashi Toshiharu
Koizumi Yutaka
Kabushiki Kaisha Toshiba
King Roy
Wilkins, III Harry D.
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