Nickel-based alloy compositions for component parts, having reduced cracking susceptibility and optimized high-temperature properties.

Abstract

The present invention provides nickel-based alloy compositions for component parts that have reduced cracking susceptibility and optimized high-temperature properties. [Solution] A nickel-based alloy composition consisting of, after removing unavoidable impurities, C: 0.04-0.10%, Ta: 8-13%, Cr: 12-20%, Co: 3-25%, Mn: less than 0.03%, Si: less than 0.06%, Mo: 0-6%, Fe: less than 5.0%, Al: 2-4%, Mg: less than 0.01%, V: less than 0.02%, W: 0-6%, Ti: less than 1%, Y: less than 0.03%, B: 0.005-0.015%, S: less than 0.003%, Zr: 0.005-0.04%, Hf: less than 3%, and the remainder being Ni. In addition, the nickel-based alloy composition has a total content of Mo and W of 4% to 10%, a ratio of Ta to the total content of Al and Ti of 1.6 to 6.5, a total content of Mn and Si of less than 0.07%, and a ratio of Cr to Al of 3 to 10.

Description

Technical Field

[0001] The present invention relates to nickel-based superalloys or alloy compositions, their use, a method of additive manufacturing components, in which the corresponding alloy powder is at least additionally processed, a method, the corresponding master alloy and component parts made from nickel-based superalloys.

Background Art

[0002] Component parts are preferably intended for use in the hot gas path of a gas turbine. For example, the component parts relate to cooled components having a thin-walled or intricate design. Alternatively or additionally, the component parts can be components for use in the automotive or aerospace fields.

[0003] In components such as rotor blades, guide vanes, ring segments, etc. in the hot gas path of a gas turbine, nickel-based superalloys with a particularly high proportion of the γ'-phase (gamma prime phase) are used in order to achieve the required high-temperature stability. This alloy was originally developed as a casting alloy and is optimized for this production route, but is basically considered to have reduced weldability or even non-weldability because it tends to crack in either the welding process or subsequent heat treatment. As a result, there are significant challenges in the defect-free additive processing of such alloys, for example laser-based powder bed methods (laser powder bed fusion, LPBF).

[0004] It has been found empirically that alloys that form a high proportion of the gamma prime phase and thus have a wide solidification interval tend to increase the tendency to cause hot stress cracking and solidification stress cracking during additive processing as a result of the microsegregation effect. The solidification or melting interval typically means the temperature interval between the solidus temperature and the liquidus temperature of a substance or substance phase.

[0005] Furthermore, subsequent heat treatments, which require, firstly, the establishment of a desired microstructure, but secondly, the dissipation of process-specific intrinsic stresses, lead to further significant macroscale cracking (post-weld heat treatment cracking or strain aging cracking, SAC) due to the superposition of these intrinsic stresses and the microstructural intrinsic stresses generated during heat treatment due to volume changes during γ' phase precipitation.

[0006] Therefore, due to the resulting defects, there is virtually no possibility of proper operation using the additive manufacturing components or parts produced from these alloys.

[0007] Turbines or mechanical components subjected to high thermomechanical stress are the subject of continuous improvement, particularly to increase their efficiency during use. However, in the case of heat engines, especially gas turbines, this results in even higher operating temperatures, among several other effects. Therefore, the metal materials and component designs of components that may be subjected to high stress, such as turbine blades, are constantly being improved in terms of their strength, lifespan, creep resistance, and thermomechanical fatigue.

[0008] Additive manufacturing is gaining attention for its potential to disrupt industries, particularly for the mass production of these components.

[0009] Additive manufacturing (AM), also colloquially known as 3D printing, includes, for example, powder bed fusion, selective laser melting (SLM) or laser sintering (SLS), or electron beam melting (EBM).

[0010] The production of gas turbine blades by the described powder bed-based method (LPBF) advantageously enables the realization of new geometries, concepts, solutions, and / or designs that can reduce manufacturing costs, construction time, and lead time, optimize the production process, and further improve the thermomechanical durability of the components.

[0011] Components produced by conventional methods, such as casting, are clearly inferior to additive manufacturing routes, for example, in terms of design flexibility, and also in terms of required lead time and associated high costs and manufacturing complexity.

[0012] Various methods currently known and documented in the literature are said to enable defect reduction or even defect-free additive processing of superalloys. This includes additive processing at increased temperature and / or optimization of process parameters in LPBF, such as laser power, scan speed, or line spacing.

[0013] In addition, heat treatments, such as hot isostatic pressing (HIP), can be extended, or the chemical composition can be adapted to improve weldability.

[0014] However, the first two methods mentioned are only practical within certain limits. Material-specific adjustments to the irradiation parameters are necessary in both cases, and this is also true for alloys that have relatively good suitability for welding. However, depending on the suitability for welding, the parameters can only be adjusted within perceptible limits, that is, within the range that allows for a proper structural outcome for the component. Pure optimization of the component structure to overcome susceptibility to hot cracking or solidification cracking is not possible simply through appropriate adjustment of irradiation parameters.

[0015] Even in this manner, the susceptibility to strain aging cracking (SAC) cannot be significantly reduced. Additive processing using high preheating temperatures, e.g., above 1000°C, is not feasible under industrial conditions. Furthermore, there are technical limitations, for example, with regard to related problems arising from temperature and sintering effects. The HIP process can contribute to closing thermal or solidification cracks present in the resulting structure to a certain extent. However, even in this way, it is not possible to close or neutralize relatively large cracks near the surface or even open cracks on the component surface. Instead, such cracks may progress further in the "HIP" process. In principle, due to the described problems associated with the susceptibility of the corresponding alloy to cracking, there are no means of additive powder bed-based processing (welding) of the corresponding material.

[0016] Minor adjustments to the chemical composition of already established casting and forging alloys have been adequately described and implemented to some extent in the literature on solutions to the effects already mentioned. This typically involves adjustments to grain boundary active elements, such as carbon (C), boron (B), or zirconium (Zr), or equivalent elements, such as silicon (Si). The goal is generally to reduce the levels of these elements.

[0017] Precipitation-hardened gamma-prime nickel-based superalloys for use in powder-bed additive manufacturing methods are known, for example, from (Patent Document 1).

[0018] Another method for increasing suitability for welding or basic weldability is the reduction of γ' formation levels. However, this method generally involves changes in high-temperature stability and / or creep resistance and ductility. Therefore, achieving slight adjustments to the chemical composition of alloys developed for various production routes is not very productive.

[0019] Except for the method according to (Non-Patent Document 1), the above-described method is additionally based on the adjustment of the conventionally known casting alloy IN738LC ("LC" = low carbon). Zhou et al. performed alloy modification based on CM247, but the present invention is the result of a completely different "ab initio" or clean-sheet alloying method in which the alloy composition was fully adapted to additive manufacturing from the beginning.

Prior Art Documents

Patent Documents

[0020]

Patent Document 1

Non-Patent Documents

[0021]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0022] Therefore, an object of the present invention is to provide a clearly improved alloy composition that is fully compatible with additive manufacturing, particularly powder bed-based processing, whereby the material class in question is suitable for welding in any case, and thus for the first time it is ensured that the corresponding additive manufacturing route can be verified.

Means for Solving the Problems

[0023] This object is achieved by the subject matter of the independent claims. Advantageous configurations are the subject matter of the dependent claims.

[0024] One aspect of the present invention relates to a nickel-based alloy, alloy composition or corresponding preform of a nickel-based superalloy in an un(melted), preferably powdered (raw) state, comprising nickel as a main component and further components in weight percent (% by weight): 0.04 to 0.10% carbon (C), preferably 0.04 to 0.07% carbon, 8 to 13% tantalum (Ta), 12 to 20% chromium (Cr), 3 to 25% cobalt (Co), less than 0.03% manganese (Mn), less than 0.03% silicon (Si), 0 to 6% molybdenum (Mo), less than 5% iron (Fe), preferably less than 0.7% iron, 2 to 4% aluminum (Al), less than 0.01% magnesium (Mg), less than 0.02% vanadium (V), 0 to 6% tungsten (W), less than 1% titanium (Ti), less than 0.03% yttrium (Y), 0.005 to 0.015% boron (B), less than 0.003% sulfur (S), 0.005 to 0.04% zirconium (Zr) and less than 3% hafnium.

[0025] In contrast, in the cited publication by Zhou et al. where a high γ' volume fraction of over 50% and low lattice misfit are described, the benefits based on tantalum as a γ'-phase forming element are not recognized, and the use of niobium (Nb) is additionally proposed. In addition, a low ratio of Ta to the sum of aluminum, niobium and titanium (Al + Nb + Ti) is proposed. Since cobalt-free alloys are not excluded in any case, the technical effects of cobalt are not recognized either. Also, clearly, in contrast to the present solution (see below), it aims to form an aluminum oxide layer as an outer layer.

[0026] The alloys described herein, in contrast, preferably allow for a moderate to high volume content of the γ' phase (gamma prime phase), e.g., about 30%, and high lattice mismatch (γ / γ'). In addition, tantalum is assumed to be a γ' phase-forming element that can take advantage of its slow precipitation behavior. Furthermore, among the elements used, cobalt is used to lower the γ' sorbus temperature in particular, without reducing the volume percentage at the operating temperature of the component during the process. Moreover, a chromium oxide layer is used as the outer layer, rather than an aluminum oxide layer (see Cr / Al ratio below).

[0027] In one configuration, the corresponding preliminary form of a nickel-based alloy, alloy composition, or nickel-based superalloy consists of nickel as the main component and further components in weight percent (W%) units: 0.05-0.10% carbon (C), 8-13% tantalum (Ta), 12-20% chromium (Cr), 3-25% cobalt (Co), less than 0.03% manganese (Mn), less than 0.03% silicon (Si), 0-6% molybdenum (Mo), 0 It contains less than 0.5% iron (Fe), 2-4% aluminum (Al), 0.0005-0.1% magnesium (Mg), less than 0.02% vanadium (V), 0-6% tungsten (W), less than 1% titanium (Ti), less than 0.03% yttrium (Y), 0.005-0.015% boron (B), less than 0.002% sulfur (S), 0.005-0.03% zirconium (Zr), and less than 3% hafnium.

[0028] In one configuration, the sum of molybdenum and tungsten is 4% to 10%, the ratio of tantalum to the sum of elemental aluminum, niobium, and titanium is 1.6 to 6.5, the sum of manganese and silicon is less than 0.03% or less than 0.07%, and / or the ratio of chromium to aluminum is 3 to 10.

[0029] High levels of tantalum, compared to the remaining elements that form the γ' phase, such as aluminum, titanium, and niobium, offer significantly greater resistance to strain aging cracking because tantalum diffuses into nickel quite slowly. The precipitation behavior of the γ' phase is slow only when tantalum plays a major role in its formation. Below this level, the precipitation behavior is too rapid, creating a risk that the produced component parts will fail as a result of strain aging cracking. If the Ta / (Al, Ti, Nb) ratio is too high, it can have the effect of forming a harmful secondary phase (e.g., the η phase).

[0030] A slow precipitation behavior scheme is chosen, which is preferably achieved through a relatively high Ta / Al ratio, resulting in a relatively low Al content. The relatively slow precipitation behavior advantageously generates smaller amounts of γ' phase in later stages during addition and subsequent heat treatment. Therefore, the intrinsic stress resulting from the AM process can dissipate before causing SAC due to the superposition of intrinsic stresses from γ' formation. To still achieve sufficiently high high-temperature oxidation and corrosion resistance, it is also necessary to select a correspondingly high Cr content to produce the specified high Cr / Al ratio.

[0031] The adverse effects on hot stress cracking resistance are generally attributed to two elements, manganese and silicon. However, literature reports suggest that manganese and silicon can, individually and in small amounts, achieve other beneficial effects on desired properties. For this reason, the content of these two elements is preferably limited to less than 0.07%.

[0032] In one configuration, the alloy composition contains, in weight percent, 0.05 or 0.04 to 0.070% carbon, 9 to 12% tantalum, 14 to 16% chromium, 8 to 21% cobalt, less than 0.01% manganese, zero or substantially zero silicon, 2 to 3% molybdenum, less than 0.5 or 0.7% iron, 3 to 3.5% aluminum, about 0.001% magnesium, zero or substantially zero vanadium, 2 to 3% tungsten, zero or substantially zero titanium, 0 to 0.01% yttrium, 0.005 to 0.01% boron, zero or substantially zero sulfur, 0.015 to 0.025% zirconium, and less than 3% hafnium.

[0033] Therefore, in contrast to obvious methods, such as the specific adjustment of individual elements in existing casting alloys, this study explored a new overall development method for novel nickel-based superalloys by addressing multiple issues. It is noteworthy that this alloy exhibits good workability by additive manufacturing, due to its low susceptibility to hot cracking (solidification cracking) and strain aging cracking (SAC), without the typical reduction in high-temperature resistance. As described in this context, this is achieved through numerous adjustments, including the adjustment of the solidification interval or its final progression, and solid solution solidification during additive manufacturing, which reduces susceptibility to hot cracking.

[0034] In addition, the substitution of conventional γ' formations (Ti) slows down the precipitation behavior of the γ' phase, so that even if precipitation occurs during the addition beam welding process, preferably no significant precipitation is present. Furthermore, the harmful superposition of process-specific intrinsic stresses during subsequent heat treatment and microstructural intrinsic stresses caused by volume changes resulting from γ' phase precipitation is reduced, thereby reducing the alloy's susceptibility to cracking due to strain aging cracking.

[0035] In addition, the proposed compositions, through the adjustment of typical and / or alternative γ' formations, enable the establishment of the maximum proportion of the γ' phase and the maximum γ / γ' lattice mismatch, thereby ensuring high strength and hardness of the alloy.

[0036] Furthermore, grain boundary active elements are carefully tuned to ensure crack-free processing while preventing unfavorable weakening of grain boundaries, and thus a reduction in high-temperature strength. In the case of nickel-based alloys, these elements include boron, carbon, and zirconium. If they are grain boundary active elements, they accumulate at the grain boundaries and strengthen them. This advantageously prevents particle slippage during the handling of component parts. In additive manufacturing, the perfect match of these elements to the remaining alloy composition is crucial; otherwise, solidification or remelt cracks may occur during processing.

[0037] The proposed alloy not only enables weldability but also achieves high strength comparable to component parts made of IN738LC, preferably. It is noteworthy that the proposed alloy has at least equal corrosion and oxidation resistance to the latter, because the elements required for this purpose, particularly Cr and Al, are present in sufficient proportions in the alloy.

[0038] In one configuration, the alloy or alloy composition consists of the components described above, excluding any unavoidable impurities or residues.

[0039] At a carbon content of 0.05–0.10 wt%, favorable formation of metal carbides occurs in such nickel-based alloys. At the defined concentration, carbon is, in this case, preferably Cr 23 Forms C6 and TaC. Cr 23 C6, in particular, precipitates at grain boundaries, thus promoting their strengthening. Metallic carbides such as TaC, already formed in the molten state, can bond with tantalum and other elements, potentially influencing the "replenishment" of the molten material. Thus, carbides can influence solidification cracks.

[0040] Tantalum carbide (TaC) is stable even at high temperatures and cannot be completely melted by heat treatment. Therefore, it is necessary for high creep resistance because it inhibits particle growth even at high temperatures near its melting point. Furthermore, carbon not only indirectly affects solidification properties through carbide formation, but also directly affects the alloy by reducing its melting point. The range of 0.05 to 0.1% is advantageous as a good compromise between sufficient particle growth, favorably low susceptibility to solidification cracking, and favorably high grain boundary cohesiveness. A carbon content of 0.05% is particularly preferred because it allows for particularly high particle growth, making the entire alloy particularly robust tolerant of a wide range of irradiation parameters, or defining a particularly robust means (process window) for welding.

[0041] An aluminum content of 2.0 to 4.0 wt% is necessary for the formation of the γ' phase (preferably Ni3Al). However, if the aluminum content is too high, it will result in an (excessively) high γ' content or volume percentage of γ', which will adversely affect strain aging cracking during heat treatment.

[0042] Like aluminum, tantalum also forms a γ' phase, but it diffuses quite slowly. Therefore, a high Ta / Al ratio is advantageous to keep the behavior of the γ' phase low, and thus the aluminum content must be similarly limited. An aluminum content of less than 2% may result in an excessively low proportion of the γ' phase, potentially leading to unsuitable mechanical properties. An aluminum content of approximately 3% is particularly preferable because it provides a sufficient γ' phase content while maintaining low susceptibility to SAC. When it is found that the susceptibility to SAC is sufficiently low in individual cases, the aluminum content may be increased.

[0043] The specified tantalum content is 8.0–13.0% by weight. Tantalum, along with aluminum, is the second γ'-forming element. The tantalum content must be limited because too high a content can lead to the formation of undesirable phases such as the η phase. The mechanical properties can be controlled and adjusted through interaction with cobalt, which replaces tantalum from the γ' matrix. The higher the selected tantalum content, the lower the cobalt content should preferably be, and vice versa. A tantalum content of less than 8% may result in an excessively low proportion of the γ' phase in the alloy structure, potentially leading to unsuitable mechanical properties. A 9% tantalum content is particularly preferred because it allows for sufficient strength without cracking.

[0044] As already mentioned, the cobalt content is preferably inversely proportional to the tantalum content. Excessive cobalt content leads to undesirable phases. Conversely, if the cobalt content is too low, the strength becomes too low. Furthermore, since cobalt and tantalum affect the solidification interval, they similarly limit the maximum content. A combination of 19% cobalt with 9% tantalum has been found to be particularly advantageous because otherwise the strength would be too low. In the case of a relatively high tantalum content, the cobalt content must be reduced accordingly, but 3% is the lower limit for a sufficiently high substitution effect.

[0045] Titanium, along with tantalum, is similarly a γ'-forming compound. However, tantalum is preferred because its diffusion rate is considerably faster than that of tantalum. Titanium can reduce the oxidation stability of nickel-based alloys, so its contribution to the titanium content is similarly limited to less than 1%. Since sufficient strength can be achieved without titanium, titanium is preferably not added to the alloy.

[0046] Vanadium, along with aluminum, tantalum, and titanium, is also a γ'-forming compound. However, because it significantly reduces oxidation stability, its content is limited to less than 0.02%, and preferably, vanadium is omitted entirely.

[0047] Chromium is used as an oxide layer-forming agent, creating a stable Cr2O3 outer layer up to approximately 900°C. This is necessary because, due to its sensitivity to SAC, a sufficiently high aluminum content cannot be achieved for Al2O3 outer layer formation. Generally, the higher the chromium content, the better the stability of the outer layer. The chromium content is limited by the occurrence of undesirable phases. Currently, 14 wt% chromium is particularly preferred because it allows for efficient alloy production and provides sufficient robustness against undesirable phases.

[0048] Increasing the chromium content has been found to have a similarly positive effect on susceptibility to solidification cracking, in that it ensures that the last 10% of the solidification interval can be carried out more rapidly. Further increases in chromium content are conceivable because increasing the chromium content leads to increased oxidation stability. Theoretically, increasing the chromium content to over 18% does not change the solidification properties of the alloy. However, if the level of the element is not further reduced, undesirable phases of chromium exceeding 20%, such as the σ phase, will form. For this reason, the maximum chromium content is preferably 20%. Alloys with similar operating temperatures contain at least 12% chromium for sufficient oxidation stability, as this value is adopted as the minimum.

[0049] Iron combined with molybdenum and tungsten forms an undesirable TCP phase (also known as the Frank-Caspar phase, or "topologically tight-packed") and, otherwise, does not favorably affect the properties of the alloy. Therefore, it is not considered an alloying element, and its content is kept or limited to less than 0.05%. In practice, the preference is to avoid using iron altogether. The TCP phase belongs to a large group of intermetallic phases known for their composite crystal structure and physical properties. In particular, these phases have a combination of periodic and aperiodic structures.

[0050] In nickel-based alloys, molybdenum and tungsten act as solid solution solidifying elements due to their long atomic radii. Their content is limited to a maximum of 10%, as excessively high content leads to the formation of an undesirable TCP phase. The alloy preferably contains at least 4 wt% of these two elements in total, as an increase in the strength of the γ matrix can positively affect susceptibility to solidification cracking via solid solution solidification, and also offers further technical benefits. The two elements exhibit distinct benefits, at least theoretically. On the one hand, molybdenum segregates significantly more than tungsten, and on the other hand, it increases the solidus temperature of the remaining molten material. Tungsten, in contrast, segregates to a lesser degree and therefore does not lead to the formation of an undesirable phase in the remaining molten material.

[0051] Magnesium plays a role in binding to sulfur in the molten material and is particularly important in powder production and with respect to weldability. The magnesium content should be matched to the sulfur content as closely as possible, and should be between 0.0005 and 0.01% by weight so that as little free magnesium and sulfur as possible remains in the alloy.

[0052] Yttrium is used in some heat-resistant Ni-based alloys to improve outer layer adhesion and thus repeated oxidation stability. Yttrium is an oxide-forming element that diffuses very slowly. In addition, yttrium oxide is very thermally stable and results in significant dislocation fixation. Slow diffusion and particularly strong dislocation fixation at grain boundaries can improve interfacial bonding strength and reduce susceptibility to cracking. Furthermore, yttrium, like magnesium, has the ability to bond to sulfur, thus having a positive effect on weldability.

[0053] Boron contributes to grain boundary cohesion and has a very positive effect on creep resistance. However, it has been found that increasing the boron content above 0.015 wt% (corresponding to 150 ppm) leads to severe solidification cracking during the AM process. On the other hand, at boron content below 0.005 wt% (corresponding to 50 ppm), weak grain boundaries remain, resulting in SAC (Solid Acid Crack) during addition welding or subsequent heat treatment. A boron content of 70 ppm is particularly preferred because it advantageously enables a large, stable process window and robust processing while ensuring proper grain boundary cohesion.

[0054] Zirconium (zircon) is generally considered to be a cause of solidification cracks or thermal cracks during the AM process, particularly in IN738LC among several materials. Therefore, this element is frequently supplied at significantly reduced levels to improve productivity. However, it has been found that adding 200 ppm zirconium to the alloy, with a boron content of 70 ppm, has a positive effect on productivity and increases the process window. In addition, a minimum zirconium content of 50 ppm is preferred because, like boron, it is a grain boundary active element that increases grain boundary cohesiveness. Since it cannot be ruled out that increasing the zircon content has a negative effect on productivity, the maximum zircon content is set at approximately 300 ppm.

[0055] Since boron and zirconium have similar effects, the sum of these two elements is similarly limited to the range of 100-300 ppm. Below this level, it results in insufficient grain boundary cohesion, and above this level, it increases the risk of thermal crack formation. A zirconium content of 200 ppm combined with 70 ppm boron is considered favorable for both grain boundary cohesion and welding productivity.

[0056] Sulfur (S) has a significantly detrimental effect on the properties of nickel-based alloys and therefore must be reduced to a content of at least 0.002% or less.

[0057] Hafnium is frequently used in nickel-based alloys for directional solidification to increase interparticle cross ductility. However, in addition-manufactured nickel-based alloys, content below 3% has been found to yield a significant improvement in solidification cracking resistance, as well as similarly improve mechanical properties. Nevertheless, establishing an optimal content is challenging, as even small variations within a selected interval can lead to a discernible degradation of solidification cracking resistance.

[0058] In one of the alloys or alloy compositions described, with a boron content of 0.007 wt%, the carbon content is approximately 0.05 wt%, the tantalum content is approximately 9 wt%, the cobalt content is 19 wt%, the chromium content is 14 wt%, and the zirconium content is 0.02 wt%.

[0059] In one configuration, the cobalt content is selected such that, or is not formed, undesirable secondary phases, particularly the η phase, do not form in the desired final form of the alloy present in the final component.

[0060] In one configuration, the chromium content is such that it forms a stable chromium oxide layer, or is selected to do so (see above).

[0061] In one configuration, the alloy or alloy composition is in powder form.

[0062] In one configuration, the alloy powder is produced by gas injection or fluid injection, preferably using the parameters described below.

[0063] In one configuration, the alloy composition contains 9–10 wt% tantalum and 17–21 wt% cobalt. This variant (less tantalum) is noteworthy for its improved productivity or workability and lower susceptibility to SAC resulting from a lower γ' content.

[0064] In the alternative configuration, the alloy composition contains 10–12 wt% tantalum and 8–10 wt% cobalt. This variant (more tantalum), in contrast, forms a higher proportion of the γ' phase, thus meaning higher high-temperature strength, but at the same time accompanied by greater susceptibility to SAC.

[0065] Furthermore, in one configuration, the total weight of boron and zirconium is 0.01 to 0.035 or 0.045%.

[0066] In one configuration, the alloy composition has a reduced γ' sorbus temperature, in contrast to equivalent and / or conventional alloys.

[0067] Further aspects of the present invention relate to the use of alloys or alloy compositions in additive manufacturing methods, preferably laser-based and / or powder bed-based methods, such as SLM, SLS and / or EBM.

[0068] A further aspect of the present invention relates to a method for additively manufacturing component parts, in which the powder of the alloy or alloy composition described is at least partially (selectively and / or partially) melted by a laser or electron beam in order to produce the component parts layer by layer.

[0069] In one configuration, a pre-fabricated (additional) structure, particularly after a hot isostatic pressing operation, is subjected to a precipitation heat treatment including solution annealing, cooling, and thermal aging to induce precipitation hardening.

[0070] In one configuration, solution annealing involves a heat treatment step within a temperature interval of 1100°C to 1300°C over a period of 2 to 8 hours.

[0071] Further aspects of the present invention relate to structures composed of solidified powders produced directly from an additive manufacturing process, which include an intermediate alloy, preferably the alloy composition described above, wherein the intermediate alloy is free from or substantially free of γ' phase precipitates. This property specifically enables weldability through the functional relationships described herein in the alloy composition.

[0072] A further aspect of the present invention relates to a component part produced from the alloy or alloy composition described herein, wherein the structure also contains a high proportion of gamma-prime phase or precipitate phase, and in particular has an increased γ / γ' lattice mismatch.

[0073] In this regard, the composition, characteristics, and / or benefits relating to an alloy composition or a corresponding superalloy may also directly relate to the additional processing or use of the composition or components produced therein, and vice versa.

[0074] The expression "and / or" used here, when used with a series of two or more elements, means that each of the listed elements can be used individually or any combination of two or more of the listed elements can be used.

[0075] Further details of the present invention will now be described with reference to the figures. [Brief explanation of the drawing]

[0076] [Figure 1] This figure shows the (reciprocal) dependence of the diffusion coefficients of various alloying elemental components on temperature. [Figure 2]The transition of the γ / γ' phase region, which depends on the tantalum content and temperature of the alloy, is parameterized by the cobalt content (content in weight percent) and shown in a simplified phase diagram. [Figure 3] This figure shows the dependence of the Vickers hardness of an alloy with a given tantalum content on the cobalt content in weight percent. [Modes for carrying out the invention]

[0077] The representations in the figures are, to some extent, merely schematic or illustrative, and are intended only to illustrate the complex technical and functional relationships of the present invention without any claim of completeness.

[0078] Figure 1 shows an illustrative diagram illustrating the dependence of the diffusion coefficient D (logarithmic) of alloying elements in nickel on the logarithm of the reciprocal of temperature (bottom) and temperature in degrees Celsius (top). In particular, the solid-state diffusion properties of rhenium, tungsten, molybdenum, cobalt, tantalum, chromium, titanium, and aluminum in nickel-based alloys are thus quantified. In one observation, tantalum as a γ'-form diffuses to a considerably lower degree, for example, in the temperature range of 1200°C to 1300°C, compared to titanium and aluminum, as it exhibits a smaller diffusion coefficient. This relationship leads to favorable thermomechanical properties of the presented alloy compositions. In particular, slower or weaker diffusion can similarly slow down the precipitation behavior of the gamma-prime phase, clearly reducing susceptibility to cracking with respect to SAC. Figure 1 describes the results of "Thermo-Calc" simulations, either entirely or partially.

[0079] Figure 2 is a schematic phase diagram showing the transition of the γ / γ' precipitated phase region, which depends on temperature or the technical synergistic effect of the elements cobalt and tantalum in the presented alloy composition.

[0080] Cobalt, at a given γ' content, induces a reduction in the γ' sorbus temperature. Lower γ' sorbus temperatures lead to slower γ' precipitation behavior and lower driving force towards γ' formation. This also reduces susceptibility to SAC, as already described above. On the other hand, for a given γ' sorbus temperature, it is possible to increase the γ' content at the operating temperature of the corresponding component. Cobalt can increase the γ' content by replacing tantalum from the γ matrix into the γ' phase. Moreover, this results in increased strength through the γ' phase because it leads to an increase in γ / γ' lattice mismatch via substitution. To illustrate the described effect of cobalt with reference to Figure 2, alloys of the corresponding composition with approximately 11% tantalum levels (see vertical line) have approximately the same sorbus temperature, so the range of 0-9% Co can be considered in particular (see double arrow). However, with 9% cobalt, the γ' content is higher than that of the zero-cobalt portion at moderate temperatures (see horizontal line). Therefore, the line drawn in Figure 2 illustrates the shift in the γ / γ' phase region toward a higher γ' content at the same sorbus temperature. Thus, while cobalt itself does not necessarily directly reduce the γ' sorbus temperature, it allows for the use of less tantalum, thus enabling the same γ' content to be achieved at a lower sorbus temperature. By increasing the Co content to 15%, it is possible to reduce the Ta content, for example, from 11% to 9%, while still establishing a γ' content of over 20% and lowering the sorbus temperature as much as possible.

[0081] Figure 3 shows the dependence of Vickers hardness H on the cobalt content of an alloy with a 9 wt% tantalum content. The substitution effect described manifested itself as an increase in hardness with increasing Co content in the alloy. In addition, the morphology of the γ' phase changed from spherical to cubic as a result of the increase in Co content (this was not explicitly identified in the figure). This suggests that the Ta content in the γ' phase increases with increasing Co content, and therefore the transformation of the γ' phase morphology from spherical to cubic proceeds more rapidly due to increased lattice mismatch.

[0082] The actual addition process for manufacturing component parts from an alloy, resulting in a certain type of (selectively melted) intermediate alloy, typically involves one or more heat treatments to establish a suitable microstructure. The first step in the heat treatment chain is preferably a HIP process to close process-related porosity. The temperature of choice here preferably corresponds to a solution annealing operation, which is ideally above the γ' sorbus temperature and below the solidus temperature, for example, 1100°C to 1300°C. Since the HIP process typically allows only gradual cooling, it is preferably followed by another solution annealing operation, also at 1100°C to 1300°C, for for example 2 to 8 hours under reduced pressure or in a protective gas atmosphere, followed by rapid cooling. For optimal creep resistance, one or more aging operations are performed following the solution annealing at a temperature of 700°C to 950°C for for example 12 to 48 hours.

[0083] The powders of the alloys or alloy compositions described herein are preferably produced in a vacuum inert gas injection plant. In this plant, the alloy is melted in a so-called VIM oven, and the liquid molten material is held for 20 minutes to 2 hours for homogenization. The molten material is directed into an injection funnel connected to a gas nozzle, and the molten metal is injected under high pressure of 5 to 100 bar together with an inert gas to give metal particles. The molten material is heated in a molten crucible to 5 to 400°C above its melting point. The metal flow rate during the injection operation is 0.5 to 80 kg / min, and the gas flow rate is 2 to 150 m³. 3 The rate is / min. Rapid cooling solidifies the spherical metal particles (spherical particles). The inert gas used during injection may contain 0.01 to 100% nitrogen as required. The gas phase is then separated from the powder in a cyclone, and the powder is then packed.

[0084] The particles here are defined as gas inclusions with a size (diameter) of 5 μm to 250 μm, representing 0.0 to 4% of the total area of ​​the object being evaluated (pores smaller than 1 μm), and containing 2 to approximately 8.5 g / cm³. 3It has a bulk density up to the alloy density and is airtightly packed with argon under a protective gas atmosphere.

[0085] The particle size range of the powder is 5 to 250 μm, with preferred ranges being 5 to 150 μm or 10 to 150 μm. The preferred range was determined by separating excessively fine and excessively coarse particles through sieving and sifting processes. These processes are carried out under a protective gas atmosphere and can be performed one or more times. The inert gas during powder production may be either argon or a mixture of argon and less than 0.01 to 100% nitrogen. Alternatively, the inert gas may be helium if possible. The inert gas should preferably have a purity of at least 99.996 volume%. In particular, the nitrogen content should be 0 to 10 ppmv, the oxygen content 0 to 4 ppmv, and the H2O content less than 5 ppmv.

[0086] The component parts produced from such alloy powder by addition pathways may be component parts for jet engines, for example, component parts for the hot gas pathway of a gas turbine. In particular, the component parts may be rotor blades or guide vanes, ring segments, burner parts or burner tips, shrouds, shields, heat shields, nozzles, seals, filters, spouts or probes, resonators, rams or agitators, or corresponding transitions or inserts or corresponding aftermarket parts.

Claims

1. Nickel as the main component, and further components in weight percentage: 0.04 to 0.10% carbon, preferably 0.04 to 0.07% carbon, 8-13% tantalum, 12-20% chromium, 3-25% cobalt, Manganese less than 0.03%, Silicon content of less than 0.06%, 0-6% molybdenum, Less than 5.0% iron, preferably less than 0.7% iron, 2-4% aluminum, Magnesium less than 0.01%, Vanadium less than 0.02%, 0-6% tungsten, Less than 1% titanium, Yttrium less than 0.03%, 0.005-0.015% boron, Sulfur content less than 0.003%, 0.005 to 0.04% zirconium, and Hafnium content less than 3% A nickel-based alloy composition comprising, in addition, - The total amount of molybdenum and tungsten is between 4% and 10%. - The ratio of tantalum to the sum of aluminum, niobium, and titanium is between 1.6 and 6.

5. - The total amount of manganese and silicon is less than 0.07%, and - A nickel-based alloy composition in which the ratio of chromium to aluminum is 3 to 10.

2. In units of weight percentage, 0.04-0.070% carbon, 9-12% tantalum, 14-16% chromium, 8-21% cobalt, Manganese less than 0.01%, Effectively zero percent silicon, 2-3% molybdenum, Less than 0.7% iron, 3-3.5% aluminum, Approximately 0.001% magnesium, virtually zero vanadium, 2-3% tungsten, Virtually zero titanium, 0-0.01% yttrium, 0.005-0.01% boron, Zero or virtually zero sulfur, 0.015 to 0.025% zirconium, and Hafnium content less than 3% The alloy composition according to claim 1, comprising:

3. The alloy composition according to claim 1 or 2, comprising the above components, with unavoidable impurities removed.

4. The alloy composition according to any one of claims 1 to 3, wherein the cobalt content is selected so as not to produce any undesirable secondary phases, in particular any η phase.

5. The alloy composition according to any one of claims 1 to 4, wherein the chromium content is selected to form a stable chromium oxide layer.

6. The alloy composition according to any one of claims 1 to 5, comprising 9 to 10% by weight of tantalum and 17 to 21% by weight of cobalt.

7. The alloy composition according to any one of claims 1 to 5, comprising 10 to 12% by weight of tantalum and 8 to 10% by weight of cobalt.

8. The alloy composition according to any one of claims 1 to 7, wherein the total amount of boron and zirconium is additionally 0.01 to 0.045% by weight.

9. The alloy composition according to any one of claims 1 to 8, which is in powder form.

10. An alloy composition according to any one of claims 1 to 9, having a reduced γ' sorbus temperature in contrast to equivalent and / or conventional alloys.

11. Use of the alloy composition according to any one of claims 1 to 10 in an addition manufacturing method, particularly a powder bed method.

12. A method for additively manufacturing component parts, wherein the powder of the alloy composition according to any one of claims 1 to 10 is at least partially melted by a laser or electron beam in order to produce the component parts layer by layer.

13. The method according to claim 12, wherein the pre-fabricated structure after hot isostatic pressing is subjected to a precipitation heat treatment including solution annealing, cooling, and thermal aging in order to induce precipitation hardening.

14. The method according to claim 13, wherein the solution annealing includes a heat treatment step at 1100°C to 1300°C for a period of 2 to 8 hours.

15. An intermediate alloy produced by the method described in claim 12, comprising the alloy composition described in any one of claims 1 to 10, and free from γ / γ' phase precipitates.

16. A component part produced from a nickel-based superalloy of an alloy composition according to any one of claims 1 to 10, wherein the structure of the component part has a high γ' content with particularly increased γ / γ' lattice mismatch.

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