JP2001214227A - Nickel base superalloy exhibiting only minimum defect of crystal grain - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide single crystal(SC) and directional solidified(DS) nickel base superalloys exhibiting only the minimum defect of crystal grains at the time of casting. SOLUTION: For minimizing the grain defect such as freckles and stray grains, carbide forming elements are added to nickel base superalloys. Concretely, carbide forming elements formed from a liquid in the massive zone on the solidified boundary of single crystal(SC) and directional solidified(DS) nickel base superalloys are added to reduce the formation of the defect such as freckles and stray grains in the alloys. The preferable nickel base superalloys contain, by weight, about 6.00 to 9.25% tantalum, about 4.75 to 6.50% tungsten, about >=2.75% rhenium, about 5.00 to 7.00% aluminum about >=0.10% hafnium and carbon by an amount (ordinarily, about 0.10 to 0.15%) sufficient for forming carbide for remarkably reducing the formation of freckles in the massive zone of the superalloys at the time of casting with the other components.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates generally to the field of nickel-base superalloys. In a preferred embodiment, the present invention provides a single crystal (S
C) and directional solidification (DS) nickel-base superalloys.

[0002]

2. Description of the Related Art In recent years, single crystal (SC) nickel-based superalloys designed for aircraft engines or large power generation turbine components have been used, and such alloys are known as freckles or stray crystal grains. It has been found that defects such as stray grains are likely to occur. Heretofore, these deficiencies have not been a major concern due to the relatively small dimensions of directional solidification components in aircraft engines or relatively low operating stresses and temperatures in power generating turbines.
However, recently, in order to improve turbine performance, it has been desired to increase the operating conditions of the turbine components for power generation to a higher temperature by making the wall thickness smaller than before. Under such operating conditions, defects such as freckles and stray crystal grains become life-limiting factors for turbine components for power generation.

[0003]

SUMMARY OF THE INVENTION Broadly, the present invention resides in the addition of carbide-forming elements to nickel-based superalloys to minimize grain defects such as freckles and stray grain defects.
More specifically, the present invention relates to the addition of carbide forming elements formed from liquids in the massy zone of the solidification interface of single crystal (SC) and directionally solidified (DS) nickel-based superalloys to provide freckles in such alloys. And the formation of stray crystal defect is reduced.

[0004] In a particularly preferred embodiment of the present invention, a nickel-based superalloy is provided which comprises, by weight, from about 4.00% to less than 9.25% tantalum, about 4.75%.
% To about 6.50% tungsten, about 2.75% or more rhenium, about 5.00% to about 7.00% aluminum, about 0.10% or more hafnium and in the superalloy massy zone during casting. Contain sufficient amounts of carbon to form carbides with other components to significantly reduce freckle formation.

[0005] The alloys of the present invention are particularly useful for casting turbine blades, particularly blades for power generation turbines. The casting may be used as it is, or may be subjected to further processing such as a high-temperature solution treatment, an aging treatment, and a coating treatment.

[0006] These and other aspects and advantages of the present invention will become apparent from the following description of a preferred exemplary embodiment of the invention.

[0007]

A preferred superalloy of the present invention comprises, by weight, from about 6.00% to less than 9.25% tantalum, from about 4.75% to about 6.50% tungsten, from about 2.50%. 75% or more rhenium, about 5.00% to about 7.00
% Aluminum, about 0.10% or more hafnium, carbon, with the balance being substantially nickel.

[0008] The superalloy composition of the present invention must contain carbon to such an extent that carbides are formed with other components to greatly reduce the formation of fleckles in the massy zone during SC or DS casting. Specifically, carbon is present with other components in an amount of about 0.10% or more, most preferably in an amount of about 0.10% to 0.15%. The relatively high levels of carbon present in the alloys of the present invention are contrary to the conventional belief that single crystal and / or directional solidification techniques must maintain relatively low levels of carbon content. .

[0009] Tantalum is present in the superalloys of the present invention at about 6.00.
It is present in an amount greater than or equal to wt% and less than 9.25 wt%. In addition, the superalloy of the present invention comprises at least about 0.10% by weight, more preferably about 0.12 to 0.30% by weight (preferably about 0.
15-0.25% by weight) of hafnium. Tantalum and hafnium are strong carbide-forming elements. It has been found that when alloyed with the level of carbon required in the present invention, the interaction reduces the tendency of the nickel-based superalloy to fleckle.

[0010] Rhenium is present in the superalloys of the present invention at about 2.75.
% By weight, typically from about 2.75 to 6.40% by weight. Rhenium is most preferably used in an amount sufficient to compensate for the reduced tungsten abundance. In this regard, specifically, tungsten may be present in an amount from about 4.74% to about 6.50%, typically from about 5.00% to about 5.50%.
It is present in an amount of 75% by weight.

Aluminum is present in an amount of from about 5.00% to about 7.00% by weight, more preferably from about 6.00% to about 6.00% by weight.
It is present in an amount of 6.40% by weight. However, the total amount of aluminum and tantalum should be about 12.45% or more.

[0012] Other components may be used in the superalloys of the present invention. For example, the superalloys of the present invention can include one or more elements selected from chromium, cobalt, molybdenum, boron, yttrium, ruthenium, and niobium.
If these optional ingredients are used, they are in the following weight percent ranges: Chromium ... 4.00 to 7.25 Cobalt ... 7.01 to 15.00 Molybdenum ... 0 to 2.00 Boron ... 0.003 to 0.010 Yttrium ... 0 to 0.03 Ruthenium ... 0 to 6.00 Niobium ... 0 to 1.00.

Particularly preferred nickel-base superalloys are in the following weight percent ranges: aluminum 6.00 to 6.40 tantalum 6.30 to 6.70 tungsten 4.75 to 5.25 Rhenium 2.75 to 3.25 Hafnium 0.20 to 0.30 Carbon 0.10 -0.15 Chromium ... 6.75-7.25 Cobalt ... 7.00-8.00 Molybdenum 1.30-1.70 Boron ... 0.003 to 0.005 Nickel (substantially).

Another preferred nickel-base superalloy is
The following weight% ranges: aluminum ... 5.50 to 6.00 tantalum ... 7.00 to 7.40 tungsten ... 5.75 to 6.25 rhenium ... .... 5.20 to 5.60 Hafnium 0.12 to 0.18 Carbon 0.10 to 0.15 Chromium 4.00 to 4.50 Cobalt 12.25 to 12.75 Molybdenum 1.50 or less Boron 0.003 to 0. 010 Ruthenium 6.00 or less Niobium... 1.00 or less Nickel (substantially).

The preferred high carbon content superalloys of the present invention are:
For example, US Pat. Nos. 5,445,120 and 5,270,701
No. 23, the entire disclosure of which is incorporated herein by reference.

"Substantially nickel" means that the superalloys of the present invention can contain traces (traces) of other components that do not substantially affect its basic and novel characteristics. Such trace components include, for example, sulfur, phosphorus, copper, and other elements commonly associated with trace amounts of similarly used alloy components.

The superalloy of the present invention is disclosed in US Pat.
09, which is incorporated in full herein by reference, manufactures components using single crystal casting techniques, as described in more detail, and U.S. Pat. No. 3,260,505, the disclosure of which is hereby incorporated by reference. The entire disclosure is hereby incorporated by reference and is particularly suitable for the production of parts by the directional solidification technique as described in more detail in US Pat.

Although the present invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, the present invention is not limited to the disclosed embodiments, but rather is defined by the following claims. It is intended to cover various modifications and equivalent configurations belonging to the technical idea and scope described above.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tresa M. Pollock, Cordoba Road, Pittsburgh, PA, USA, No. 1356 (72) Inventor Christine Louise Zemsky United States of America, Glenmont, NY Bacon Road, No. 42 Bee (72) Inventor Wendy Howard Muffy, Cincinnati, Ohio, United States, Boxwood Circle, No. 3621

Claims (12)

[Claims] 1. About 6.00% or more and 9.25% by weight
Less than about 4.75% to about 6.50% tungsten, less than about 2.75% rhenium, about 5.00% to
About 7.00% aluminum, about 0.10% or more hafnium, and an amount of carbides sufficient to form carbides with other components to significantly reduce freckle formation in the superalloy massy zone during casting. A nickel-based superalloy containing carbon, the balance being substantially nickel. 2. The superalloy of claim 1 wherein the carbon is present in an amount greater than or equal to about 0.10%. 3. The superalloy according to claim 1, wherein the carbon is present in an amount of about 0.10-0.15%. 4. The superalloy according to claim 1, wherein hafnium is present in an amount of about 0.12 to 0.30%. 5. The superalloy comprises about 5.00 to 6.40% aluminum, provided that the total amount of aluminum and tantalum is not less than about 12.45%.
The described superalloy. 6. The superalloy according to claim 1, further comprising one or more elements selected from chromium, cobalt, molybdenum, boron, yttrium, ruthenium and niobium. 7. The following constituents: 6.00% to 6.40% aluminum, 6.30% to 6.70% tantalum, 4.75% to 5.25% tungsten, 2.75% to Consists essentially of 3.25% rhenium, 0.20% to 0.30% hafnium, 0.10% to 0.15% carbon, and substantially balance nickel (or greater, by weight) Single crystal or directionally solidified nickel-based alloy. 8. The following components: 6.75% to 7.25% chromium, 7.00% to 8.00% cobalt, 1.30% to 1.70% molybdenum, and 0.003%. 8. The alloy of claim 7, further comprising ~ 0.005% boron (by weight, above). 9. The total amount of aluminum and tantalum is about 1
The alloy according to claim 7, which is at least 2.45%. 10. The alloy of claim 7, wherein hafnium is present in an amount of about 0.25%. 11. The following constituents: 5.50% to 6.00% aluminum, 7.00% to 7.40% tantalum, 5.75% to 6.25% tungsten, 5.20% to 5.60% of rhenium, 0.12% to 0.18% of hafnium, 0.10% to 0.15% of carbon, and substantially balance nickel (or more by weight) Single crystal or directionally solidified nickel-based alloy. 12. The following components: 4.00% to 4.50% chromium, 12.25% to 12.75% cobalt, up to about 1.50% molybdenum, 0.003% to 0.010 The alloy of claim 11, further comprising about 6.0% or less of boron, about 6.00% or less of ruthenium, and 1.00% or less of niobium (or greater, by weight).