BRPI0715480B1 - ALLOY BASED ON NICKEL - Google Patents

Description

"CONNECT TO NICKEL BASIS".

FIELD OF INVENTION

The present invention relates to gas turbines. More particularly, embodiments of the present invention relate to nickel based alloys for use in casting gas turbine components.

BACKGROUND OF THE INVENTION

[002] Gas turbine engines are known to operate in extreme environments, exposing engine components, especially those in the turbine section, to high temperatures and operating voltages. In order for turbine components to withstand these conditions, they must be manufactured from a material with properties capable of withstanding prolonged exposure to such high operating temperatures and stresses, while receiving adequate cooling to reduce their effective operating temperatures. This is especially true for turbine vanes, or blades, as well as nozzles, or fins, which lie directly in the hot gas path stream of a combustion section.

[003] In an effort to improve the efficiency of a gas turbine engine, operating temperatures may be increased in the combustion section to more fully burn the fuel. As a result, the temperatures in the turbine section are also increased. For turbine materials to operate at a higher temperature without compromising component integrity, both additional turbine component cooling and increased material capacity are required. However, by redirecting air to cool turbine components, the amount of air available for the combustion process is reduced, reducing its efficiency. This is counterproductive to the goal of improving gas turbine efficiency by raising the operating temperature. Therefore, it is desirable to provide operational improvements without reducing present airflow levels and engine efficiency.

One result of the higher firing temperatures is the additional structural change in the material. That is, as operating temperatures increase for a given material, its load-bearing capacity decreases. As operating temperatures for gas turbine engines have increased over time to improve engine efficiency, numerous materials have been introduced with higher temperature compatibility. An example such as this is an alloy commonly referred to as CM-247 produced by the Cannon-Muskegon Corporation of Muskegon, Michigan. One form of this alloy is disclosed in US 4,461,659. This alloy is one of many that have been developed with greater strength by reducing grain boundary cracking.

[005] Another alloy enhancement for gas turbine applications has been developed by General Electric Company. GTD-111, a nickel based alloy with higher resistance to hot corrosion, was developed for use in the production of gas turbine blades and fins. The properties of this alloy are disclosed in US patents 6,416,596 and 6,428,637.

In addition to improved alloys, casting techniques have been developed to improve the strength of vanes and nozzles and other gas turbine components. As is well understood by those skilled in the art of gas turbine airfoils, the strength of a cast casting and any inherent weakness therein are a function of the size and location of the grain contours of the casting. Specifically, casting techniques have evolved from a conventional, or equiaxial, process where a metal is cast and grain outlines are free to form as the cold part, to a directional solidification (DS) casting process where the metal is poured and cooled in such a way as to form only grain outlines in one direction, preferably so that the crystallographic direction <001> is parallel to the longitudinal direction of the airfoil. By aligning grain boundaries, typically the weakest portion of a casting in a direction generally perpendicular to the airfoil load, significant improvements in mechanical strength, ductility, and thermal fatigue strength of the casting are realized. More recently, improvements have been made in the casting process to eliminate grain contours completely by cooling the castings to form a single crystal, or grain structure, thereby eliminating grain contours. This type of casting is the toughest type of casting to date, however it is the most expensive casting to manufacture because of the various processing requirements and costs of alloys. Typically, single crystal castings are limited to applications where extremely high temperatures are encountered, there are excessively high mechanical loads, or turbine geometry dictates a cast part as parking. An additional issue with the casting and alloying process used says respect to the processing required. That is, depending on the casting technique and the alloy involved, time consuming and expensive processes have to take place to form the turbine component of that particular alloy.

Although significant improvements have been made in alloy development, cooling technology and casting processes, there is still significant scope for further improvement. Specifically, there is a need in the industry for an alloy with at least the capabilities of state-of-the-art alloys, which has even greater tensile strength, better castability, lower operating stresses and lower fabrication costs.

[008] The present invention provides embodiments of a nickel based alloy suitable for the production of gas turbine components with improved stability, mechanical properties and lower operating stresses. A stress reduction such as this is found in longitudinal stress, which is a function of alloy density which, for the alloys disclosed herein, is smaller than other well-known alloys used in gas turbine applications. In addition, the nickel-based alloy undergoes a heat treatment process without the use of excessively long high temperature furnace settings, while having a larger window in which such heat treatment can occur. [009] Nickel-based alloy compositions suitable for multiple forms of precision casting are disclosed. It includes a composition suitable for equiaxial castings and for directional solidification (DS) castings. In a further aspect of the present invention, a method of fabricating a heat-treated cast and article from the nickel-based alloy is provided, comprising the elemental composition as well as the heat treatment process.

BRIEF DESCRIPTION OF THE DRAWING

[0010] The present invention is described below with reference to the figures in the accompanying drawing, in which: Figure 1 is a graph representing the maximum strength limit and temperature-dependent yield limit for an alloyed embodiment. of the present invention compared to a prior art alloy.

Figure 2 is a graph representing the breaking stress as a function of the normalized time and temperature parameter for an alloy embodiment of the present invention compared to prior art alloys.

Figure 3 is a cross section of a gas turbine engine identifying the location where vanes and nozzles according to the present invention are present.

Figure 4 is a perspective view of a formed superalloy vane according to one embodiment of the present invention.

Fig. 5 is a perspective view of an alternate vanes formed from the superalloy according to one embodiment of the present invention.

Figure 6 is a graph depicting the maximum temperature-dependent strength limit for a directionally solidified embodiment of an alloy of the present invention compared to a prior art alloy.

Figure 7 is a graph depicting the maximum temperature-dependent strength limit for an equiaxial embodiment of an alloy of the present invention compared to prior art alloys.

Figure 8 is a graph representing the temperature-dependent flow limit for an equiaxial embodiment of an alloy of the present invention compared to prior art alloys.

Figure 9 is a graph depicting the temperature-dependent flow limit for a directionally solidified embodiment of an alloy of the present invention compared to a prior art alloy.

Figure 10 is a graph depicting elongation of material as a function of temperature for a directionally solidified embodiment of an alloy of the present invention compared with an alloy of the prior art.

Figure 11 is a graph depicting elongation of material as a function of temperature for an equiaxial embodiment of an alloy of the present invention compared to prior art alloys.

Figure 12 is a graph depicting the unbroken creep life of a spade manufactured from the equiaxial mode of an alloy of the present invention compared to a prior art alloy.

DETAILED DESCRIPTION OF THE INVENTION

The subject matter of the present invention is specifically described herein to meet statutory requirements. However, the description itself is not to limit the scope of this patent. Instead, the inventors have contemplated that the subject matter claimed may also be designed in other ways to include different steps or combinations of steps similar to those described herein in conjunction with other current and future technologies. In addition, while the terms "step" and / or "block" may be used herein to connote different elements of methods employed, the terms shall not be construed as implying any particular order between two or more of the various steps disclosed herein unless except when the order of individual steps is explicitly described.

The present invention provides a nickel based alloy suitable for the production of gas turbine components and method of producing a heat treated nickel based alloy and cast part. An exemplary embodiment of the present invention is described below.

For the sake of clarity, it is best to identify part of the common terminology which will be discussed in more detail with respect to embodiments of the present invention. A "gas turbine engine," as the term is used herein, is an engine that provides mechanical output in the form of both thrust to propel a vehicle and shaft power to drive an electric generator. Gas turbine engines typically comprise a compressor, at least one combustor, and a turbine. A "shovel," as the term is used herein, is an airfoil attached to a disc that rotates about an axis of the gas turbine engine. Blades are used both to compress the air flow through a compressor and to rotate the disc and the shaft of a turbine by air passing along the airfoil surface. The term "shovel" is generally used interchangeably with "reed", and this is done here, and is not to limit the nature of the term. A "vane" as used herein is an airfoil that is typically found in both compressor and turbine sections, and serves to redirect air flow through a compressor or turbine. The term "fin" is generally used interchangeably with "nozzle", and so is done here, and is not to limit the nature of the term. These types of aerodynamic planes are usually fused from a liquid metal. Metal can be cast and cooled in a variety of media, including to form equiaxial (EQ) and directionally solidified (DS) castings. In an equiaxial casting, as can be understood in the art, the casting is naturally cooled so that the grain outlines of the solidified metal are free to form in either direction. In a DS cast part, the metal is cooled in one direction to form a set of grain outlines that extend in a specific direction.

An alloy with excellent casting properties, lower density and better stability was developed by the inventors. The alloy has an acceptable range of chemical compositions depending on the type of casting process to be used, each of which results in better mechanical properties. This has been achieved with chemical compositions that are free of expensive elements such as rhenium (approximately $ 1,778 / kg) or very reactive elements such as zirconium and hafnium.

The nickel-based alloy of the present invention, in the form originally conceived by the inventors, essentially consists approximately of the weight composition set forth in table 1 below.

Table 1 - Alloy composition The development of this alloy focused on identifying an effective nickel based alloy without expensive or overly reactive alloy additions, so that the alloy could be suitable for casting directionally solidified components as well as as equiaxials. Initially, seven chemical compositions were produced in directionally solidified ingot molds.

One area addressed during alloy development that is important with respect to alloy functionality was its structural stability. Alloys undergo complex solid phase reactions during service that may lead to precipitation of brittle phases. Controlling the chemical composition of the alloy to prevent the formation of these topologically dense packing (TCP) phases can be achieved with some success by calculating the electronic gaps per alloy atom, a value called Nv3. The structural stability of an alloy is generally calculated according to equation [0030] by SAE AS 5491 Rev. B. The higher Nv3, the less stable the alloy and the more susceptible it is to TCP structures. Previous studies have shown that even For more stable alloys of this type, TCP phases can form if Nv3> 2.45 to 2.49. Some commercial alloys such as Rene 80 and Inconnel 738 become unstable if Nv3> 2.32 to 2.38.

For the seven previously mentioned chemical compositions, the stability data are listed below in Table 2. As will be shown, depending on the shape of the cast, the fact that the metallurgical stability, or structural stability, of the alloy ranges from 2 .22 - 2.40.

Table 2 - Alloy Round Stability 0032] Although alloys 5 and 6 did not exceed the Nv3 value of 2.32, where TCP phases are known to form, a detailed review of the specimens revealed slight instabilities. Alloy 2 with an Nv3 value of 2.31 showed the best results with respect to structural stability, yet without showing TCP phase indications.

In order to improve the mechanical properties of the nickel-based alloy, it is necessary to heat treat the alloy. In order to heat treat a precipitation hardened alloy such as a nickel-based alloy of the present invention, the alloy must first be heated to a temperature close to the solvus temperature a the temperature above which the main hardening phase γ 'is present. dissolves. This is commonly referred to as a solubilization heat treatment. Subsequent exposure to a lower aging temperature will cause the hardening phase y 'to precipitate in a manner that enhances mechanical properties. The strength of the alloy increases with the amount of γ '. Its distribution and crystalline parameters are also factors that affect the degree of resistance that can be conferred by precipitation of γ '.

In the heat treatment window, the difference between the solvus and solidus temperature (temperature at which melting begins) is greatly increased in the present invention. It is this window in which the solubilization heat treatment has to be carried out in order to safely treat the part without melting. Relatively small changes in the amounts of aluminum, titanium and tantalum can cause very large changes in solvus γ 'temperature. If the alloy contains higher levels of aluminum, titanium or tantalum, then the solvus γ ’temperature increases, thereby decreasing the heat treatment window. In order to determine the solvus and solidus γ \ temperatures, differential thermal analyzes (DTA) were performed. As those skilled in materials engineering understand, an OTD measures the difference in temperature between a sample and a thermally inert reference as the temperature rises. The graph of this differential provides information about reactions occurring in the sample, including phase transitions, melting points and crystallization. Some typical results of these analyzes are shown below in table 3.

Table 3 - Heat Treatment Characteristics Ό035] As can be seen from the data presented, the heat treatment window of alloy 2, the most structurally stable of the alloys, also had a large heat treatment window, approximately 83Ό, depending on the composition. of the alloy, the heat treatment window can range from 67-89Ό. A window grain like this indicates that the alloy can be safely heat treated under production conditions without the possibility of melting. This is especially critical because often the heat treatment of large parts in large batches cannot be done with very precise temperature control, often varying up to ± 14 “Ό.

Another benefit of the alloy heat treatment of the present invention is with respect to its tensile and creep rupture properties. It has been found that no appreciable benefit is achieved by heat treating the solubilization of the alloy of the present invention at higher temperatures, or by subjecting it to more complex aging treatments, as is the case for other high temperature nickel alloys. . The alloys developed by the present invention were heat treated by solubilization at 1121 ° C ± 14 ° C for 2 hours ± 15 minutes, followed by a gas-cooled quench below 593 ° C. Quenching preferably takes place in a gas environment selected from the group comprising argon, helium and hydrogen. The alloys were then raised to 1079 ± 14 ° C and aged for 4 hours ± 15 minutes followed by gas quenching back below 593 ° C. Finally, the alloy was elevated to 84313 ± 14 ° C and stabilized for 24 hours ± 30 minutes followed by cooling below 593Ό but most likely at room temperature. This heat treatment cycle occurs at a relatively low temperature and involves fewer cycles compared to those of other well known alloys, thus making this cycle a very economical heat treatment cycle. This is best understood by comparing the heat treatment cycles disclosed herein with those of other similar alloys shown in table 4 below.

Table 4 - Some Commercial Alloy Heat Treatment Requirements 0037] Depending on the type of gas turbine component being melted, the timing of the heat treatment cycles may vary. For example, if a gas turbine blade or vane is to be coated with a thermal barrier coating (TBC) for additional protection from high operating temperatures, then the second and third steps in the heat treatment process may occur after TBC. The step of raising the alloy temperature to 1079Ό ± 14 ° C and holding for 4 hours also serves to treat the coating as part of the coating process. Another important feature of the present invention is its density. As versed in the gas turbine airfoil technique, the longitudinal stress on an airfoil is proportional to the squared density, or [stress σ α (density p) 2]. That is, the lower the density of the alloy used to produce the airfoil, the lower the longitudinal stresses presented by the airfoil.

Specific densities for alloy 2 were both calculated and measured from the sample coatings. To more accurately calculate the density in this particular chemical composition range, an equation was developed. This equation is not sensitive to cobalt and chromium levels, and is defined as: D = 0.307667639 + (% Mo) (0.000452137} + (% W) {0.001737591) - (% Al) (0, 004497133) - (% Ti) (0t001240936) + (% Ta) (0.002133375) with% Mo being% by weight molybdenum,% W being% by weight tungsten,% Al being% by% aluminum weight,% Ti being the weight percentage of titanium and% Ta being the weight percentage of tantal.

The degree of fit of the equation is excellent, as can be seen by comparing the measured densities of the sample cast with the calculated densities shown in table 5 below.

Table 5 - Experimental Alloy Density * Fused using Alternative Supplier As previously discussed, the density of this new alloy is significant due to the lower inherent operating stresses. The density of the alloy in the present invention is less than or equal to 8.3 g / cm3. The lower density level of this alloy can be better perceived when compared to other alloys commonly used in gas turbine applications shown in table 6 below.

Table 6 - Densities of Multiple Gas Turbine Alloys Ό042] Another important factor regarding alloy density concerns the weight and frequency of the resulting component. The lower the density, the lower the component weight. For a spinning turbine blade, the blade attachment pushes a disk while the blade is being held in the disk. This push is a function of the weight of the blade. A lower shovel weight will have less pushing on the disc and as a result will have lower attachment stresses.

Density also affects the natural frequency of an airfoil, whether it is a shovel or a fin. As those skilled in the art understand, the natural frequency of a rotary is critical as it must remain outside the critical motor frequency (60 Hz for a motor operating at 3,600 revolutions per minute). The airfoils are not only intended to be outside the engine operating frequency (60 Hz in this example), but also their order (ie 120 Hz, 180 Hz). The present turbine blades made from a higher density alloy have a natural frequency just above the motor frequency. If a blade or vane resides at the motor's natural frequency, or any order of the motor over a long period of time, blade failure may occur because of high cycle fatigue. Manufacturing turbine blades / vanes from a lower density alloy not only reduces component weight and blade attachment stresses, but also increases their natural frequency, which shifts the blade or fin frequency further to out of motor frequency, thus reducing the chance of high cycle fatigue failure.

The mechanical properties for two data points for the first round of alloys are shown in tables 7 and 8 below. Table 7 represents maximum strength limit (UTS) data and yield limit (YS) data at temperatures of 42713 and 760Ό, while table 8 represents creep break data at 760Ό. Each of these tables also includes data referring to a "baseline". Comparisons are made in the following tables and figures between the developed alloys and a baseline alloy and GTD-111. The baseline is an alloy currently used by the applicant in certain aerofoil productions, with the baseline having similar properties to those of GTD-111.

As previously discussed, a goal of this development program is to produce a stable, higher strength alloy that has better casting capacity and lower manufacturing costs. Referring to Table 7, two alloy 2 casting experiments are highlighted as well as one alloy baseline. As can be seen from the data, alloy 2 (both casting experiments) has a UTS within approximately 3% of the baseline alloy at a temperature below 427 ° C, while still having a higher YS. While alloy 7 has a larger UTS, it has a smaller heat treatment window (7513 versus 8513 for alloy 2). Alloy 3 also has a smaller heat treatment window than alloy 2 and has a smaller UTS. Disadvantages in the other development alloys become apparent at higher operating temperatures., At typical turbine operating temperatures, closer to 76013, alloy 2 (both casting experiments) has a UTS and YS greater than baseline. Also, as previously discussed, alloy 2 was structurally all stable and had the largest heat treatment window, serving the best fabrication conditions. As can be seen, the other alloys at 760 ° C neither had the strength of alloy 2 nor began to exhibit structural instabilities (TCP phases), as previously discussed in table 2 and reproduced below.

Table 7 - Mechanical Properties of the Alloy Casting Experiment In addition to the strength of the various alloys, another measure of alloy capacity is creep rupture (see table 8 below). Creep is a plastic deformation caused by slippage that occurs along crystallographic directions because of a constant ear-ga / stress applied at an elevated temperature. Creep is typically measured as a percentage of strain and the number of hours required at this load and temperature to cause strain. From the data in table 8, it can be seen that all alloys showed improvement in creep life and hours for 0.5%, 1% and 5% creep deformation. Although alloy 3 had better creep life than alloy 2, alloy 3 had other drawbacks with respect to heat treatment windows and structural stability, shown in Table 7, Table 8 - Creep Burst Data from Casting Experiments From these and other data, it was determined that alloy 2 was the preferred composition that provided the necessary strength, structural stability, and allowed for a more convenient manufacturing process.

More detailed analysis and development of alloy 2 was then conducted to determine the final composition. More specifically, four small runs (13.6 kilograms) were fused as directionally solidified plates and evaluated. These race sizes have been selected as the most representative of the sizes and weights for typical gas turbine castings applications. Of these runs, the number of electronic gaps, Nv3, ranged from 2.220 - 2.280. The resulting chemical compositions of these four alloys are shown below in table 9.

Table 9 - Alloy Variations Chemical Compositions The mechanical properties of 2A - 2D alloys were compared with a baseline to determine a preferred alloy. Referring to Table 10, it can be seen that alloy 2C provided higher YS and UTS at 4270 relative to the baseline as well as a larger YS in the transverse direction at 760 * 0. A graph of the capacity of alloy 2C as a function of GTD-111 is shown in figure 1. Tensile stress data for 2C and 2D alloys are compared with a baseline alloy and GTD-111 in figure 2. From this In the graph, it can be seen that 2C alloy has a longer stress rupture life than the baseline and thus is similar to that of GTD-111.

Table 10 - Tensile Properties of Alloy 2 Variations Ex-0051] Having determined that Alloy 2 is the preferred alloy and more particularly that Alloy 2C is the preferred elemental composition because of its higher strength limit at 427Ό It has been noted that the industrial production quantities of the alloy can be produced in either directionally solidified (DS) or conventional or equiaxial foundries. To evaluate castings on a production scale, two 172 kg main alloy runs were produced. As skilled in the art of precision casting, it is understood that in order to fuse a nickel-based alloy such as that of the present invention with different solidification techniques, DS versus equiaxial, it is necessary to modify the carbon content. Specifically, an equiaxial casting requires a higher carbon content, approximately 0.07 - 0.10%, whereas a DS casting requires only about 0.03 - 0.06%. For the fused sample runs in each configuration, the chemical analyzes are shown in table 11.

Table 11 - Chemical Analysis of (181 kilogram) Production Races Having concluded that the 2C alloy could be successfully fused to either DS or equiaxial type, the next step in the development of the alloy was to transfer experience race casting to smelting of gas turbine components from experience. A cross section of a typical gas turbine engine is shown in figure 3, with each engine section noted. For 2C alloy, two turbine section blades compatible with each of the General Electric Frame second and third stage turbine were fused. The second stage blades are approximately 45.7 centimeters long and each weighs approximately 8.6 kilograms. A diagram of this type of gas turbine blade is shown in Figure 4. This blade is typically cast in a directionally solidified manner because of the operating temperatures and stress levels observed by the blade. It is fused to CM 247, a nickel-based alloy that has a higher density than the alloy disclosed herein, the details of which have been previously discussed and disclosed in US Patent 4,461,659. An average production yield (% of acceptable castings) for this CM-247 cast airfoil is approximately 80%. Experimental turbine blade castings of this stage resulted in a 100% yield. Although the sample size was small, there was no indication that this yield would be different in a production environment.

As for the third stage shovel, it is approximately 58.4 centimeters in length and weighs approximately 11.8 kilograms. A diagram of this type of gas turbine blade is shown in Figure 5. This blade is typically cast in the same manner as a conventional or equiaxial type of CM 247. However, the typical yield of this part is only approximately 20% when it is CM 247 casting. The use of the alloy of the present invention increased the casting yield to 100%. Although the sample size was small, there was no indication that this yield would be different in a production environment.

By further testing and analysis, slight modifications to the 2C alloy composition were made to produce a more reproducible composition as well as to further improve the capabilities of the material. The resulting composition differs slightly between the equiaxial form and DS, but both are covered by the alloy composition listed below in table 12.

Table 12- Alloy Composition 0055] By such analysis and testing, a better understanding of the material capacities for 2C alloy in both equiaxial and directionally solidified form was measured. The equiaxial form of alloy 2C was designated as PS M1 16 and the DS form of alloy 2C was designated as PSM117. PSM117 was analyzed for both longitudinal and transverse directions. As skilled in the art they understand, "longitudinal" and "long" refer to along the grain contours, while "transverse" or "cross member" is the 90 degree direction to the grain direction. Modifications made to create the form of production of the equiaxial alloy and DS included minor changes in elemental concentrations, some increasing, some decreasing. Through mechanical testing of production specimens, it was determined that the maximum strength limit improved over alloy 2C, and prior art GTD-111 alloy. This was true for both equiaxial and DS shapes at the upper end of the operating spectrum of a turbine blade, greater than approximately 64913 (see figures 6 and 7). As can be seen from Figure 7, the equiaxial shape of the alloy of the present invention also has a higher maximum strength limit over most of the temperature profile, compared to prior art Canon-Muskegon 247 and Inconnel 738 alloys.

In addition, for the same operating spectrum, the flow limit of the equiaxial alloy, PSM116, was also slightly higher compared to the prior art alloy 2C, GTD-111, CM-247 and IN-738 alloys (see figure 8). Referring to Figure 9, similar improvements in yield strength compared to the prior art GTD-111 alloy can be seen for the DS alloy specimens of the present invention. These improvements in yield strength and maximum strength limit at the upper end of the operating envelope are important, since turbine blades made from this alloy tend to operate at these higher temperatures (64913 or higher).

Referring now to Figures 10 and 11, elongation of the material at high temperature is shown, respectively, for directionally solidified and equiaxial forms of the present invention. In general, for both alloy shapes, the percent elongation is greater at higher operating temperatures than at lower temperatures. Referring to Figure 10, the DS shape of the alloy has slightly greater elongation than the prior art alloy GTD-111. However, at higher operating temperatures, above approximately 760 ° C, the percent elongation of the DS form (PSM117) is lower than that of GTD-111. It is this arrangement that is most desirable for gas turbine technology. For turbine blades and fins operating at higher temperatures, lower elongation values are indicative of a stronger component. Referring to Figure 11, the percent temperature elongation for the equiaxial alloy form of the present invention, PSM116, is shown. The percent elongation is greater for the equiaxial alloy in most of the temperature profile compared to the previous technology alloys.

Referring to Figure 12, an additional benefit of the alloy of the present invention is shown in terms of creep rupture life over the percentage extent of the alloy formed blade. Component life is measured in hours to breakage. As can be seen from Figure 12, for a given temperature and mechanical load, the equiaxial shape of alloy 2C, PSM116, shows improvement in the unbroken life (shown in dimensionless scale) of the route of an alloy-formed blade to at least 80 % of the extension site compared to the equiaxial shape of the prior art GTD-111 alloy.

In addition to the alloy composition which is disclosed, there is disclosed a method of making a nickel based alloy heat-treated cast and article comprising providing the alloy according to the previously described composition levels and subjecting the alloy to the previously disclosed heat treatment process.

The present invention has been described with respect to particular embodiments, which are intended in all respects to be illustrative rather than restrictive. Alternative embodiments will be apparent to those skilled in the art to which the present invention pertains without departing from its scope.

From the foregoing, it is understood that this invention is well adapted to achieve all the purposes and objectives presented, along with other advantages that are obvious and inherent to the system and method. Certain features and subcombinations are understood to be of use and may be employed without reference to other features and subcombinations. This is contemplated and in accordance with the scope of the claims.

Claims (5)

1. Nickel-based alloy with a density of 0.30 lb / in3 (8.3 g / cm3) for the production of lower longitudinally traction gas turbine components, characterized in that it consists of the following composition as a percentage by weight: aluminum 3.35-3.65 titanium 4.85-5.15 tantalum 2.30 - 2.70 chrome 11.50-12.50 cobalt 11.50-12.50 iron 0.0-0.15 copper 0.0-0.10 tungsten 3.3 - 3.7 molybdenum 1.70-2.10 carbon 0.04-0.12 boron 0.010-0.020 zirconium 0.0 - 20 parts per million hafnium 0.0 - 0.05 sulfur 0.0-0.0012 nitrogen 0.0 - 25 parts per million oxygen 0.0-10 parts per million, and the remaining nickel and incidental impurities. Nickel-based alloy according to claim 1, characterized in that said weight percent carbon composition is 0.08 - 0.12 and said weight percent zirconium composition is up to 10%. parts per million. Nickel-based alloy according to claim 2, characterized in that it further comprises a weight percent silicon composition of up to 0.05. Nickel based alloy according to claim 1, characterized in that said weight percent carbon composition is 0.04-0.07, said weight percent sulfur composition is up to 10%. parts per million, and said weight percent nitrogen composition is up to 10 parts per million. Nickel-based alloy according to claim 4, characterized in that it further comprises a weight percent silicon composition of up to 0.06, a weight percent phosphorus composition of up to 15 parts per million, and a weight percent lead composition of up to 1 part per million.