EP4619245A1

EP4619245A1 - Oxidation resistant nickel (ni) base superalloy, powder, components and methods

Info

Publication number: EP4619245A1
Application number: EP23834048.3A
Authority: EP
Inventors: Magnus Hasselqvist
Original assignee: Siemens Energy Global GmbH and Co KG
Current assignee: Siemens Energy Global GmbH and Co KG
Priority date: 2023-01-27
Filing date: 2023-12-18
Publication date: 2025-09-24
Also published as: CN120603970A; GB2626730A; WO2024156439A1; KR20250139854A; GB202301208D0

Abstract

The invention relates to a Nickel base alloy, comprising (in wt%): 6.0% to 10.0% Cobalt (Co), 6.0% to 10.0% Iron (Fe), 12.0% to 16.0% Chromium (Cr), 4.2% to 5.4% Aluminum (Al), 4.0% to 7.0% Tantalum (Ta), 0.05% to 1.0% Hafnium (Hf), 0.005% to 0.1% Silicon (Si), and 0.03% to 0.3% of the sum of rare earths such as Scandium (Sc), Yttrium (Y), the Actinides and/or the Lanthanides, at least 0.01% Carbon (C), at least 0.005% Zirconium (Zr), Nickel (Ni).

Description

Oxidation resistant Nickel (Ni) base superalloy, powder, components and methods

The present invention relates to a nickel-base gamma prime strengthened superalloy, a powder, components and methods to produce components .

It further relates to its use for Liquid Metal Deposition (LMD) of components such as, but not restricted to, blades, vanes, heat shields, sealings and combustor parts in turbines or gas turbines. It further relates to its use for powder bed processes such as, but not restricted to, Laser Powder Bed Fusion (LPBF) of components such as, but not restricted to, blades, vanes, heat shields, sealings and combustor parts in turbines or gas turbines. It further relates to its use for casting of components such as, but not restricted to, vanes, heat shields, sealings and combustor parts in turbines or gas turbines. It further relates to its use for hot components which need to resist metal dusting.

Blade alloys are essential for critical components in aero and land-based gas turbines, but are used also in other applications .

The difference between blade alloys depend on the level of knowledge and production technology available at the time they were developed, and, on different relative emphasis on properties such as hot corrosion resistance, oxidation resistance, weldability, phase stability and creep strength.

AM processability is linked to weldability since they are to a large extent welding processes. Blade alloys are used in monocrystalline (SX) , directionally solidified, columnar (DS) or equiaxed (CC) microstructure. Each grain is a crystal mainly consisting of a matrix of the gamma phase, which is essentially Nickel (Ni) with elements like Cobalt (Co) , Iron (Fe) , Chromium (Cr) , Molybdenum (Mo) , Tungsten (W) and/or Rhenium (Re) in solid solution, and particles of the gamma prime phase, which is essentially Ni₃Al with elements like Ti, Ta and Nb in solid solution. Each grain is a two-phase crystal in which the gamma matrix and the gamma prime particles share the same crystal orientation and the boundaries between the matrix and the particles are coherent. Grain boundaries, if present, are usually decorated by carbides and/or borides which provide cohesive strength. Zirconium (Zr) also contributes to grain boundary cohesion.

Creep strength is provided by elements like Molybdenum (Mo) , Tungsten (W) and/or Rhenium (Re) which provide solution strengthening of the gamma matrix, and, Titanium (Ti) , Tantalum (Ta) and/or Niobium (Columbium, Nb) , which provide solution strengthening of the gamma prime particles. Aluminum (Al) provides creep strength as it increases the amount of gamma prime particles, and, as the presence of gamma prime particles concentrates the levels of Molybdenum (Mo) , Tungsten (W) and/or Rhenium (Re) in the matrix. The creep resistance is enhanced by a coarse-grained structure as obtained by polycrystalline casting or directionally solidification casting, or, even more efficiently, the absence of grain boundaries as in monocrystalline casting.

AM processes such as LMD or LPBF tend to result in a finegrained structure. The resulting reduction in creep strength can, depending on the component to be designed, be compensated for by the design possibilities provided by AM process- es . Blade alloys get their protection against oxidation and corrosion through formation of a protective, i.e. , continuous and adherent, Cr₂O3 layer and/or a protective, i.e. , continuous and adherent, AI2O3 layer, in the oxide scale.

It is generally accepted that protective Cr₂O3 formation require at least 12.0wt% Chromium (Cr) . Cr₂O3 layers, if they can be formed, typically stay long term protective up to temperatures in the order of 1173K in the flowing hot gas environment in the gas turbine hot path.

Continuous A1₂O3 layers, if they can be formed, typically only form above temperatures in the order of 1123K. As the temperature decrease the Aluminum (Al) activity also decreases and eventually protective A1₂O3 can no longer form.

Corrosive agents such as the alkali salts occurring in gas turbines are generally taken to be especially active in the 973K to 1123K range where they can occur as molten deposits. Since this is a temperature range in which protective Cr₂O3 can form if the Chromium (Cr) content is at least 12.0wt%, the general rule of thumb is that resistance to hot corrosion, which is the label used for corrosion due to alkali salts, is compromised if the Chromium (Cr) content is below 12.0wt%. Molybdenum (Mo) in the alloy will be present in the spinel' s above the protective layer and can react with and exacerbate corrosive deposits. Hence to much Molybdenum (Mo) is detrimental to the hot corrosion resistance.

It is known that the hot corrosion resistance of the low Chromium (Cr) aero alloys CMSX-4 and MD2SX is significantly inferior to that of the alloys IN792 and IN738LC which have more than 12. Owt% Chromium (Cr) at 1123K. D. Goldschmidt teaches in "Single-Crystal Blades" in Proc, from Materials for Advanced Power Engineering 1994, Part I, p.661-674 that the hot corrosion resistance of the blade alloy SC16 with 16.0wt% Chromium (Cr) and 3. Owt% Molybdenum (Mo) is significantly inferior to that of the blade alloy IN738LC with 16.0wt% Chromium (Cr) and 1.8wt% Molybdenum (Mo) .

It has recently been shown that hot corrosion can be an issue also at temperatures down to at least 773K.

It is known that the hot corrosion stress corrosion cracking resistance of the New IGT alloys STAL15SX and STAL125Ccl having > 12. Owt% Chromium (Cr) is significantly superior to the low Chromium (Cr) Aero alloys CM247CC and CMSX-4.

If the amount of alloy elements is too high, unwanted phases (UP) such as Sigma and Laves phases will form in service. Therefore, an increased level of alloy elements other than Chromium (Cr) must be accompanied by a reduction in Chromium (Cr) if too much UP formation is to be avoided, implying a conflict between corrosion resistance and other properties. One particular effect of UP precipitation is a reduction in creep strength. Another effect is embrittlement of the blade alloy. Another effect is reduction of oxidation and corrosion resistance if Chromium (Cr) is tied up in Chromium (Cr) rich

UP.

In the context of high firing temperature gas turbines, it is generally accepted that high oxidation resistance implies the ability to form protective AI2O3 layer, as needed to withstand metal temperatures on or exceeding the 1273K level. Furthermore, the oxide scale spallation caused by the always present sulfur contamination must be suppressed. Furthermore, there must be a margin against loss of the ability to reform protective alumina since each reformation implies a loss of Aluminum (Al) . Furthermore, the use of alloy elements such as Titanium (Ti) will cause contamination of the AI2O3 layer as Titanium (Ti) partially substitutes for Aluminum (Al) in said layer, rendering the layer less protective. Furthermore, it is beneficial to enable fast selective oxidation of AI2O3 as this will reduce the thickness of the oxide scale and make it less prone to spallation.

The ability for formation of protective A1₂O₃, and the margin against loss of Aluminum (Al) via scale spallation, is a complex function of the Aluminum (Al) content and the combination of other alloy elements which, acting in synergy, enhance or reduce this ability. In CALPHAD terms this ability is associated with the predicted Aluminum (Al) activity. In the context of blade alloys CALPHAD means use of thermodynamic software such as Thermocalc for prediction of entities such as partitioning of alloy elements between gamma and gamma prime; liquidus, solidus and gamma prime solvus temperatures; gamma prime content; risk for precipitation of UP; Aluminum (Al) activity. An increased Aluminum (Al) activity also implies faster selective oxidation of protective AI2O3.

The following observations on alloy element additions for improved oxidation resistance can be found in the literature:

C.A. Barrett: Statistical Analysis of Elevated Temperature Gravimetric Cyclic Oxidation Data of 36 Ni- and Cobalt (Co) - base Superalloys based on an Oxidation Attack Parameter NASA TM 105934 teaches that the ability to form protective AI2O3 is provided by Aluminum (Al) , enhanced by Chromium (Cr) and Tantalum (Ta) , somewhat reduced by Molybdenum (Mo) and Tungsten (W) , and significantly reduced by Titanium (Ti) and Nio- bium (Nb) . This was based on a large correlation study on commercial as well as experimental blade alloys. This implies that less Aluminum (Al) is needed to form a protective AI2O3 layer if the levels of Chromium (Cr) and Tantalum (Ta) are increased, or, the levels of Titanium (Ti) and Niobium (Nb) are reduced.

C. Sarioglu, et al. : The Control of Sulfur Content in Nickel-Base Single Crystal Superalloys and its Effect on Cyclic Oxidation Resistance Proceedings 'Superalloys 1996' teaches that the scale adherence is severely reduced by tramp elements such as Sulfur (S) , but, that this effect can be neutralized by a combination of clean casting and addition of small, measured levels of reactive elements (RE) . Without RE additions, it is necessary to be well below Ippm Sulfur (S) to avoid a detrimental effect on the scale adherence.

B.A. Pint et al: Effect of Cycle Frequency on High- Temperature Oxidation Behavior of Alumina- and Chromia- Forming Alloys Oxidation of Metals, 58 (1/2) , 73-101 (2002) underlines the importance of S, and further teaches the beneficial RE effects when small levels of Hafnium (Hf) and the rare earth Yttrium (Y) are combined.

P. Caron et al. : Improvement of the Cyclic Oxidation Behaviour of Uncoated Nickel Based Single Crystal Superalloys Materials Proceedings 'Materials for Advanced Power Engineering 1994' teaches the beneficial RE effects when small levels of Hafnium (Hf) and Silicon (Si) are combined.

B.A. Pint et al. : The use of Two Reactive Elements to Optimize Oxidation Performance of Alumina-Forming Alloys Materials at High Temperature 20 (3) 375-386, 2003 teaches that significant RE effects can be obtained when a multiple RE recipe is used, one example being the excellent cyclic oxidation resistance seen in tests on Haynes-214 which contained small levels of Zirconium (Zr) , Silicon (Si) and Yttrium (Y) .

It is generally accepted that the risk for hot tearing during AM processes such as LMD or LPBF, and strain age cracking during a subsequent solutioning, increase with increasing nominal gamma prime content, taken as the equilibrium content at 1123K Carbon (C) , and the gamma prime solvus temperature. Our in-house experience is that IN939, having a gamma prime content of about 35mol% and a Solvus of about 1353K can be readily processed while IN738LC, having a nominal gamma prime content of 44mol% and a solvus of about 1433K, can be handled if with more qualification efforts and stricter requirements on the levels of grain boundary elements like Boron (B) and Zirconium (Zr) as well as on the allowable level of Silicon (Si) . Higher gamma prime contents tend to require even more efforts, including more elaborate and costly AM production processes and even more qualification efforts. It is thus useful to keep the gamma prime content on at most the IN738LC level, and preferably on the IN939 level.

Most blade alloys can be characterized as Classical Industrial Gas Turbine (IGT) alloys, Aero alloys or New IGT alloys.

These alloys have > 12.0wt% Chromium (Cr) for formation of protective Cr₂O₃, see figure. The classical IGT blade alloys do not have the ability to form protective A1₂O₃ although SCA425 with 4. Owt% Aluminum (Al) supported by 16.0wt% Chromium (Cr) is border line. In house oxidation testing at 1273K has shown that SCA425 will form a continuous layer of A1₂O₃ on most but unfortunately not all of its surface. Its Aluminum (Al) activity at 1273K is 3.1e-8 based on Thermocalc with TTNi8 as data base. The Classical IGT alloys do not fulfil our objective since they are not able to form protective A1₂O₃.

The class of Aero alloys include the CM247CC, used for CC and DS casting, and CMSX-4 and Rene N5, used for SX casting, see Table. Their hot corrosion resistance is poor due to their low Chromium (Cr) levels. Most of them can form protective AI2O3 thanks to high levels of Aluminum (Al) and Ta, and, despite low levels of Chromium (Cr) . The Aero alloys do not fulfil our objective since their corrosion resistance is poor. Furthermore, their high gamma prime contents, typically in the 60mol% to 70mol% range, imply that they are difficult to process by AM processes such as LMD or LPBF.

The class of New IGT alloys include the SX alloy STAL15SX, the CC alloys STAL125CC1 and STAL15CC, and the LMD alloy STAL18SiLaY, see Table. These alloys have sufficient Chromium (Cr) for formation of protective Cr₂O3 at low and intermediate temperatures, typically up to about 1173K. Furthermore, they form protective AI2O3 at high temperature, typically above about 1123K, thanks to moderate to high levels of Aluminum (Al) supported by significant levels of Chromium (Cr) and Tantalum (Ta) .

It is therefore aim of the invention to overcome these problems .

The problem is solved by an alloy, a powder, components and methods according to the independent claims.

In the dependent claims further advantages are listed which can be arbitrarily combined with each other to yield further advantages . An objective of this invention to provide a blend of good hot corrosion resistance, excellent oxidation resistance, good processability for AM processes such as LMD and LPBF, high phase stability, and a good creep resistance by AM standards. Alternatively, it is an objective of this invention to provide a blend of high hot corrosion resistance, excellent oxidation resistance, high AM processability, high phase stability, and a moderate creep resistance by AM standards. Within the present invention creep strength can accordingly to some extent be traded for increased hot corrosion resistance.

These blends are useful for repair of oxidation damage in components such as, but not limited to, blades, vanes, heat shields, sealings and combustor parts in turbines or in gas turbines, using AM processes such as, but not restricted to, LMD and LPBF. They are furthermore useful for cladding of components such as, but not restricted to, blades, vanes, heat shields, sealings and combustor parts in turbines or in gas turbines, using AM processes such as, but not restricted to, LMD or LPBF to preempt oxidation damage in service. They are furthermore useful for fabrication of highly oxidation resistant components such as, but not restricted to, vanes, heat shields, sealings and combustor parts in turbines or in gas turbines, using AM processes such as, but not restricted to, LMD or LPBF. They are furthermore useful for precision casting of components such as, but not restricted to, vanes, heat shields, sealings and combustor parts in turbines or in gas turbines. They are furthermore useful when corrosive fuels are used, one example being corrosive biofuels. They are furthermore useful to manage corrosive agents such as sea salt in the inlet air. They are furthermore useful for alternative applications such as managing of hot flowing hydrocarbons which provide a corrosive and carbonizing environment with a low partial pressure of oxygen (O2) . As one possible area of application: Efficient internal cooling of edges and tips on hot stage gas turbine parts is difficult to achieve, hence a significant amount of the cooling air used in a gas turbine is spent on dilution air which is mixed with the hot gas stream in the vicinity of tips and edges to locally reduce the temperature of said hot gas stream in order to avoid too much oxidation damage. Any improvement in metal temperature tolerance can therefore be translated into reduced dilution air usage resulting in im- proved gas turbine thermal efficiency and consequently in reduced CO₂ emissions.

The class of Classical IGT alloys include the polycrystalline IN939, IN738LCarbon (C) and IN792 (see table)

Table: Element additons in [wt%] . STAL15CC is abbreviated as S15CC, Edgel25 abbreviated as E125 etc. Aluminum activity values are relative values at 1273K, y' i-^s the equilibrium content at 1123K. STAL125CC1 is taken as the norm for good hot corrosion resistance thanks to having 12.5wt% Chromium (Cr) and < 2. Owt% Molybdenum (Mo) .

STAL15SX is taken as the norm for high hot corrosion resistance thanks to having 15. Owt% Chromium (Cr) and < 2.9wt% Molybdenum (Mo) .

CM247CC, as fabricated by a low sulfur process with <5ppm Sulfur (S) , is taken as the norm for high oxidation resistance thanks to its ability to form protective alumina, and efficiently suppress the oxide spallation caused by sulfur. It is a commonly chosen blade alloy when a high oxidation resistance is needed. Excellent oxidation resistance is taken as the ability of an alloy to be essentially unharmed in severe cyclic oxidation tests in which CM247CC is essentially destroyed.

The norm for high AM processability is taken as a combination of high LMD and LPBF processability. The norm for high LMD processability is taken as the ability to perform crack free LMD using weld seams in the order of 0.5mm to 1mm in width and height, with no subsequent strain age cracking, for a range of high strength blade alloy substrates. The norm for high LPBF processability is taken as the ability to print the dog bone and cruciform geometries, two established crack provocation tests, crack free and with no subsequent strain age cracking.

High phase stability is taken as phase stability, as calculated using ThermoCalc with TTNi8 as thermodynamic database, on the same level as the New Industrial Gas Turbine (IGT) alloys STAL15SX and STAL125CC1, which show no precipitation of unwanted phases (UP) , such as Laves or Sigma, in creep tests with rupture times exceeding lOkh in the 923K to 1123K range and do not form UP in service.

Moderate creep resistance is taken as creep resistance on the level of fine grained IN939 as e.g. , obtained by LPBF of IN939Good creep resistance is taken as creep resistance on the level of fine grained IN738LC as e.g. , obtained by LPBF of IN738LC.

In the present invention, a judicious combination of Iron (Fe) and Cobalt (Co) is used to improve the oxidation resistance and AM processability significantly relative to STAL15CC. When Iron (Fe) and Cobalt (Co) are added, the partitioning of Aluminum (Al) is altered and, as a result, the gamma prime content is reduced such that the AM processability is increased. When Aluminum (Al) is forced into the gamma prime matrix, the oxidation resistance is increased.

The alloy comprises between 6.0wt% and 10.0wt% Cobalt (Co) , between 6.0wt% and 10.0wt% Iron (Fe) , between 12.0wt% and 16.0wt% Chromium (Cr) , between 4.2wt% and 5.4wt% Aluminum (Al) , between 4. Owt% and 8. Owt% Tantalum (Ta) , at least 0.01wt% Carbon (C) , at least 0.005wt% Zirconium (Zr) , between 0.05wt% and 1.5wt% Hafnium (Hf ) , between 0.005wt% and 0. lwt% Silicon (Si) , between 0.01wt%, especially 0.02wt%, and 0.3wt% of the sum of rare earths such as Scandium (Sc) , Yttrium (Y) , the actinides and the lanthanides, optionally at least 0.5wt% Molybdenum (Mo) or at least 0.5wt% Tungsten (W) or at least 0.3wt% Rhenium (Re) or at least 0.0015wt% Boron (B) .

Especially between 3.0wt% and 6.0wt% of Molybdenum (Mo) + Tungsten (W) and/or Rhenium (Re) , at most 2. Owt% Molybdenum (Mo) are comprised by this alloy. Further advantages are yielded with 0.02wt% and 0.3wt% of

Carbon (C) + Zirconium (Zr) + Boron (B) .

The function of the following alloying elements are valid separately for all inventive alloys:

Chromium (Cr) is used at at least 12.0wt% to enable formation of protective Cr₂O3 and thus enable good hot corrosion resistance. The Chromium (Cr) content is limited to 16.0wt% to avoid the risk for too much UP precipitation. Chromium (Cr) also contributes to the Aluminum (Al) activity.

Optionally Molybdenum (Mo) is used at at least 0.5wt% to pro- vide strength to the gamma matrix but is preferably limited to at most 2. Owt% to avoid a detrimental effect on the hot corrosion resistance.

Optionally Tungsten (W) is used at at least 0.5wt%, more preferably at at least 2. Owt% to provide strength to the gamma matrix but is preferably limited to at most 4.5wt% to avoid the risk for too much UP.

Rhenium (Re) can be used preferably up to 1.0wt%. At higher levels its effect on the phase stability might be too detrimental .

Aluminum (Al) is used at at least 4.2wt% to enable a high Aluminum activity. The upper limit is set at 5.4wt% to avoid too much gamma prime formation and an associated loss of AM process ability.

Tantalum (Ta) is used at at least 4. Owt% to provide strength and contribute to the Aluminum activity. The upper limit is set to 8. Owt% to avoid too much UP formation. Hafnium (Hf) is used at a small measured value of at least 0.05wt% to provide a Sulfur (S) gettering effect, but can be set to a higher level to e.g. , provide an increased resistance to rumpling in an applied aluminide or platinum aluminide coating. The upper limit is set at 1.5wt% to avoid the risk for too much UP formation.

Carbon (C) is preferably included at at least 0.01wt% to provide grain boundary strengthening. The upper limit is set preferably at 0.15wt% as higher levels might result in a too brittle behavior.

Boron (B) is included at at least 0.0015wt% to provide grain boundary strengthening. The upper limit is set preferably to 0.03wt% since higher levels could reduce the AM processability too much.

Zirconium (Zr) is included at at least 0.005wt% to provide grain boundary strengthening and to act as a Sulfur (S) scavenger. The upper limit is set preferably to 0.1wt% as in IN939 since higher levels could reduce the AM processability too much.

The sum of Scandium (Sc) , Yttrium (Y) , the Actinides and the Lanthanides is included at at least 0.02wt% for sulfur scavenging. The upper limit is set to 0.3 wt% since higher levels might result in too much rare earth oxide inclusions, which might result in a brittle behavior.

Silicon (Si) is included at at least 0.005wt% to provide a beneficial catalytic effect on the formation of protective

AI2O3. The upper limit is set at 0.1wt% since higher levels might result in embrittlement of the grain boundaries. The blade alloy according to the invention is preferably processed with a clean production process. To guarantee best re- suits, the blade alloy should contain less than 5ppm Sulfur, preferably less than Ippm Sulfur (S) .

The inventive idea is exemplified below: STAL15CC, see Table, is a high strength, highly oxidation resistant, highly hot corrosion resistant blade alloy. However, with 52 mol% gamma prime it does not meet the AM processability objective. Furthermore, the objective is an extreme rather than a high oxidation resistance.

In one embodiment of the present invention called Edgel25, see Table, Cobalt (Co) is increased, and Iron (Fe) introduced relative to STAL15CC.

This alters the partitioning of Aluminum (Al) forcing more Aluminum (Al) into the gamma matrix. The gamma prime content is thus reduced. Tantalum (Ta) is then subsequently reduced to provide about the same amount of Tantalum strengthening per mol% gamma prime as in STAL15CC and this further reduces the gamma prime content somewhat. The Chromium (Cr) content is then reduced to maintain the good phase stability of STAL15CC despite more Aluminum (Al) , Iron (Fe) and Cobalt (Co) in the gamma matrix. The result is a gamma prime content of 44mol% as predicted with ThermoCalc using TTNi8 as data base. This is the same level as in IN738LC, suggesting a similar AM processability. The Chromium content in Edgel25 is the same as in IN792 and STAL125CC1, and the Molybdenum (Mo) content is low at 1.0wt%, suggesting a good hot corrosion resistance. Edgel25 contains 1.0wt% Molybdenum, 3.7wt% Tungsten and 6.5wt% Tantalum as strengthening elements. This is significantly higher than in Edgel4. The RE recipe in Edgel25 is extended relative to STAL15CC by the addition of a small amount of Yttrium (Y) . In one embodiment called Edgel5W, see Table, the Aluminum (Al) content is reduced relative to Edgel25 and the gamma prime content is thus further reduced.

Tantalum (Ta) is then further reduced to provide about the same amount of Tantalum (Ta) strengthening per mol% gamma prime as in STAL15CC and Edgel25. Chromium (Cr) can now be increased to 15.0wt% while the phase stability seen in Edgel25 and STAL15CC is kept. The gamma prime level is reduced to 34mol%, as predicted by ThermoCalc with TTNi8 as data base. This is similar to IN939. The hot corrosion resistance is higher than in Edgel25 thanks to a higher Chromium (Cr) content. Edgel5W contains 1. Owt% Molybdenum, 3.7wt% Tungsten and 5.0wt% Tantalum (Ta) . This is a higher level of strengthening elements, especially in the gamma matrix, than in Edgel4.

Other embodiments can be derived by those skilled in the art to e.g. , enable better matching to specific substrates and/or coatings, and, to further enhance the Sulfur (S) gettering.

In Edgel5Mo, see Table, Tungsten (W) is partially replaced by Molybdenum (Mo) relative to Edgel5W. Similarly, Rhenium (re) can be introduced at the expense of Molybdenum (Mo) and/or Tungsten (W) to get a better matching to Rhenium containing blade alloys.

The addition of Yttrium (Y) can be replaced by a combination of Yttrium (Y) and Lanthanum (La) to further improve the RE recipe. A further possibility is the use of mixed metal. This is a mix of rare earths, usually dominated by a combination of Lanthanum (La) , Yttrium (Y) and Cerium (Ce) , and the use of mixed metal can be beneficial from a cost as well as a performance point of view. Edgel25, Edgel5W and Edgel5Mo have predicted Aluminum activities of 8.4e-8, 8. Oe-8 and 7.6e-8 respectively at 1273K. These are almost twice those in e.g. , STAL15CC and STAL125CC1, see Table, strongly suggesting an extreme oxidation resistance.

Edgel5Mo has been successfully applied by LMD onto CM247CC (DS and CC cast) , STAL125CC1 and IN792 by LMD with no cracking at the interphase, or, within the applied Edgel5Mo. Furthermore, no cracking was seen during the subsequent solu- tioning, done at the solutioning temperatures for the substrates. This was achieved within a wide process window for weld seams of about 0.5 by 0.5mm. Based on in-house experience this implies at least IN939 level LMD processability. Crack provocation geometries have furthermore been printed by LPBF using Edgel5Mo, and, no cracking was seen during the printing, or, during a subsequent solutioning at 1523K. The complete absence of cracks for these geometries has not even been seen for LPBF of IN939 despite lengthy process parameter optimization work.

Specimen consisting of Edgel5Mo applied on CM247CC via LMD have been evaluated in cyclic oxidation tests. Since it was difficult to find test conditions which resulted in damage to Edgel5Mo, the test parameters were made increasingly severe until a cyclic oxidation test with 1000 cycles with a hold time of Ih at 1523K per cycle was eventually used. Higher temperatures could not be used as this might have caused incipient melting in the substrate which is solutioned at about this temperature. In this test the Edgel5Mo material was still essentially unharmed while several mm was lost in those areas of the CM247CC substrate which were not protected by the Edgel5Mo layer, or, by contact with the ceramic specimen holder. It should be added that the slightly uneven surface on Edgel5Mo is not caused by oxidation, it is slightly uneven since only polishing was done after the LMD application prior to the testing. CM247CC was used for the demonstration of the edge alloy concept since it is one of the most widely used polycrystalline alloys when a high oxidation resistance is required .

It should be mentioned that Edgel4 has also been applied by LMD on CM247CC, and such specimen have been evaluated with the same very severe test conditions as the CM247CC/Edgel5Mo specimen and with almost identical results. In the CM247CC/Edgel4 case this can be seen as natural given the high Aluminum content of 6.5wt% supported by 14.0wt% Chromium. Edgel5Mo does however have a moderate Aluminum (Al) content of 4.5wt%, but its Aluminum (Al) activity is remarkably enough on the same level as that of Edgel4 thanks to the combination of 8. Owt% Cobalt (Co) and 8. Owt% Iron (Fe) , and it did turn out that the Aluminum (Al) activity really is a trustworthy marker for oxidation resistance. A similar Aluminum (Al) activity gave similar test results (when the reactive element recipe was also the same and the powder was procured from the same supplier with similar quality in terms of contaminants) .

It should also be mentioned that the omission of an Aluminum (Al) activity for CM247CC in Table is based on the fact that the data base TTNi8 is known to work less than well for

CM247CC.

It should also be mentioned that the oxidation life of applied AI2O3 forming coatings such as aluminides benefit from having this edge alloy as a substrate below. The reason is that a major mode of degradation of such coatings is the loss of Aluminum from said coatings through diffusion into the substrate, hence, if the Aluminum activity of the substrate is increased this loss of Aluminum (Al) via diffusion is retarded. It should also be mentioned that aluminides and platinum aluminides can suffer from spallation due to rumpling but that this can be mitigated by having Hafnium in the substrate as this will diffuse into the coating and reduce the rumpling .

In addition to the use of this edge alloy for local augmentation of the oxidation resistance and coating compatibility of components cast or additively manufactured in other blade alloys, it can also be used for additive manufacturing or casting of entire components if these are at most moderately creep loaded. This includes, but is not restricted to, sealing structures, heat shields, moderately creep loaded vanes and combustor parts in gas turbines.

In one embodiment called Edgel5 Tungsten (W) , Aluminum (Al) is reduced relative to Edgel25 and the gamma prime content is thus further reduced.

Tantalum (Ta) is then further reduced to provide about the same amount of Tantalum (Ta) strengthening per mol% gamma prime. Chromium (Cr) can be increased to 15.0wt% while the phase stability of STAL15CCis kept. In Edgel5W the gamma prime level is reduced to about the same level as in IN939 which is readily processed by LMD and LPBF. The overall level of strengthening of Edgel5W is similar to that of IN939 even if the balance between strengthening of the gamma and gamma prime is different. The gamma matrix in Edgel5W is strengthened by lwt% Molybdenum (Mo) + 3.7wt% Tungsten (W) while IN939 is only strengthened by 2wt% Tungsten (W) . The gamma prime particles in Edgel5W is strengthened by 5.0wt% Tantalum (Ta) , which is however still on the same level in strengthening per mol% gamma prime as in STAL15CC and at a higher level than in Rene N5, while IN939 is strengthened by 3.7wt% Titanium (Ti) + 1.4wt% Tantalum (Ta) + 0.9wt% Niobium (Nb) . Edgel5W is thus comparable to IN939 from a strength and AM processability point of view.

The Aluminum (Al) activities in Edgel5W and Edgel5 Molybdenum (Mo) are reduced relative to that of Edgel25, but they are still significantly above that of STAL15C Carbon (C) , see Figure .

It might seem surprising that Iron (Fe) and Molybdenum (Mo) can increase the Aluminum (Al) activity as much as suggested by CALPHAD. However, the oxidation resistance and the Aluminum (Al) activity are associated with the Aluminum (Al) content in the gamma matrix, and this is comparatively low even in blade alloys capable of forming protective AI2O3 since most of the Al normally partitions to the gamma prime particles. The relative increase in gamma matrix Aluminum (Al) content, as Cobalt (Co) and Iron (Fe) force more Aluminum (Al) into said gamma matrix, is substantial.

Edgel5Mo has been applied by LMD on the Aero alloy CM247DS, which is the CM247CC composition cast by DS in order to produce specimen for oxidation testing. Since it was difficult to find test conditions which resulted in damage to the Edgel5Mo material, the test parameters were made increasingly severe until a cyclic oxidation test with 1000 cycles with a hold time of Ih per cycle was done at 1523K. Higher temperatures could not be used as this would have caused incipient melting in the substrate which is solutioned at about this temperature. In this test the Edgel5Mo material was still essentially unharmed while several mm was lost in those areas of the CM247CC substrate which were not protected by the Edgel5Mo layer or by contact with the ceramic specimen hold-

Edgel5M0 has furthermore been used to print the crack provocation geometries in the dog bone and cruciform specimen. Consistent crack free printing followed by no strain age cracking in the subsequent solutioning was shown. This is not always seen even when IN939 is printed and seldom seen when alloys with higher gamma prime contents are printed.

According to one embodiment of the invention the alloy may include between 6.0wt% and 10.0wt% Cobalt (Co) , between 6.0wt% and 10.0 wt% Iron (Fe) , between 12.0wt% and 16.0wt% Chromium (Cr) , between 3.0wt% and 6.0wt% of Molybdenum (Mo) + Tungsten (W) + (and/or) Rhenium (Re) , at most 2.0wt% Molybdenum (Mo) , between 4.2wt% and 5.4wt% Al, between 4.0wt% and 7.0wt% Tantalum (Ta) , between 0.05wt% and 0.15wt% of Carbon (C) + Zirconium (Zr) + Boron (B) , at least 0.03wt% Carbon (C) , at least 0.01wt% Zirconium (Zr) , between 0.05wt% and 1.0wt% Hafnium (Hf ) , between 0.005wt% and 0. lwt% Silicon (Si) , and between 0.03wt% and 0.3wt% of the sum of rare earths such as Scandium (Sc) , Yttrium (Y) , the actinides and the lanthanides, Nickel (Ni) , especially the rest being Nickel (Ni) and unavoidable impurities.

Additionally, the alloy may include between 7.0wt% and 9.0 wt% Cobalt (Co) , between 7.0wt% and 9.0wt% Iron (Fe) , between 12.0wt% and 13.5wt% Chromium (Cr) , between 0.7wt and 1.3wt% Molybdenum (Mo) , between 3.4wt% and 4.0wt% Tungsten (W) , between 4.9wt% and 5.3wt% Aluminum, between 6.0wt% and 8.0wt% Tantalum (Ta) , between 0.04wt% and 0.08wt% Carbon (C) , between 0.005wt% and 0.015wt% Zirconium (Zr) , between 0.005wt% and 0.015wt% Boron (B) , between 0.05wt% and 0.2wt% Hafnium (Hf ) , between 0.005wt% and 0.05wt% Silicon (Si) , and between 0.03wt% and 0.2wt% of Yttrium (Y) , Nickel (Ni) , especially the rest being Nickel (Ni) and unavoidable impurities.

In a preferred embodiment called Edgel25, the alloy may include 8. Owt% Cobalt (Co) , 8. Owt% Iron (Fe) , 12.5wt% Chromium (Cr) , 1. Owt% Molybdenum (Mo) , 3.7wt% Tungsten (W) , 5. lwt% Al, 6.5wt% Tantalum (Ta) , 0.05wt% Carbon (C) , 0.01wt% Zirconium (Zr) , 0. lwt% Hafnium (Hf ) , 0.01wt% Silicon (Si) and 0.05wt% Yttrium (Y) , Nickel (Ni) , especially the rest being Nickel (Ni) and unavoidable impurities.

Alternatively, the alloy may include between 7. Owt% and 9.0wt% Cobalt (Co) , between 7. Owt% and 9.0wt% Iron (Fe) , between 13.5wt% and 16.0wt% Chromium (Cr) , between 0.7wt% and 1.3wt% Molybdenum (Mo) , between 3.4wt% and 4.0 wt% Tungsten (W) , between 4.2wt% and 4.8wt% Aluminum (Al) , between 4.0wt% and 6.0wt% Tantalum (Ta) , between 0.03wt% and 0.08wt% Carbon (C) , between 0.005% and 0.015wt% Zirconium (Zr) , between 0.005wt% and 0.015wt% Boron (B) , between 0.05wt% and 0.2wt% Hafnium (Hf ) , between 0.005wt% and 0.05wt% Silicon (Si) , and between 0.03wt% and 0.2wt% of Yttrium (Y) , Nickel (Ni) , especially the rest being Nickel (Ni) and unavoidable impurities.

In a preferred embodiment called Edgel5W, the alloy may include 8.0wt% Cobalt (Co) , 8.0wt% Iron (Fe) , 15.0wt% Chromium (Cr) , 1.0wt% Molybdenum (Mo) , 3.7wt% Tungsten (W) , 4.5wt% Aluminum (Al) , 5.0wt% Tantalum (Ta) , 0.05wt% Carbon (C) , 0.01wt% Zirconium (Zr) , 0. lwt% Hafnium (Hf ) , 0.01wt% Silicon (Si) and 0.05wt% Yttrium (Y) , Nickel (Ni) , especially the rest being Nickel (Ni) and unavoidable impurities.

Alternatively, the alloy may include between 7.0wt% and 9.0wt% Cobalt (Co) , between 7.0wt% and 9.0wt% Iron (Fe) , 13.5wt% and 16.0wt% Chromium (Cr) , between 1.2wt% and 1.8wt% Molybdenum (Mo) , between 2.2wt% and 2.8wt% Tungsten (W) , between 4.2wt% and 4.8wt% Aluminum (Al) , between 4. Owt% and 6.0wt% Tantalum (Ta) , between 0.04wt% and 0.08wt% Carbon (C) , between 0.005wt% and 0.015wt% Zirconium (Zr) , between 0.005wt% and 0.015wt% Boron (B) , between 0.05wt% and 0.2wt% Hafnium (Hf ) , between 0.005wt% and 0.05wt% Silicon (Si) , and between 0.03wt% and 0.2wt% of Yttrium (Y) , Nickel (Ni) , especially the rest being Nickel (Ni) and unavoidable impurities.

In a preferred embodiment called Edgel5W, the alloy may include 8. Owt% Cobalt (Co) , 8. Owt% Iron (Fe) , 15. Owt% Chromium (Cr) , 1.5wt% Molybdenum (Mo) , 2.5wt% Tungsten (W) , 4.5wt% Al, 5. Owt% Tantalum (Ta) , 0.05wt% Carbon (C) , 0.01wt% Zirconium (Zr) , 0.1 wt% Hafnium (Hf ) , 0.01wt% Silicon (Si) and 0.05wt% Yttrium (Y) , Nickel (Ni) the rest being Nickel (Ni) and unavoidable impurities.

The blade alloy according to the invention is preferably processed with a clean production process. To guarantee best results, the blade alloy should contain less than 5ppm Sulfur (S) , preferably less than Ippm Sulfur (S) .

Alternatively, further embodiments can be designed to optimize compatibility with specific coatings when the alloy is used as a base alloy. Alternatively, further embodiments can be designed to optimize compatibility with specific base alloys and coatings when the alloy is used as filler alloy for cladding and weld repair.

In this case the inventive alloy is added to substrate, which has a different composition.

Claims

Patent claims

1. Nickel base alloy, comprising (in wt%) : 6.0% to 10.0% Cobalt (Co) , 6.0% to 10.0% Iron (Fe) , 12.0% to 16.0% Chromium (Cr) , 4.2% to 5.4% Aluminum (Al) , 4.0% to 8.0% Tantalum (Ta) , especially 4.0% to 7.0% Ta, 0.05% to 1.5% Hafnium (Hf ) , 0.005% to 0.1% Silicon (Si) , 0.01% to 0.3%, especially 0.02% to 0.3%, of the sum of rare earths such as Scandium (Sc) , Yttrium (Y) , the Actinides and/or the Lanthanides, wherein especially at least two rare earths are added, at least 0.01% Carbon (C) and especially maximum 0.15wt% Carbon (C) , at least 0.005% Zirconium (Zr) and especially maximum 0. lwt% Zirconium (Zr) , Nickel (Ni) , especially remainder Nickel (Ni) , and unavoidable impurities, optionally at least 0.5% Molybdenum (Mo) and/or at least 0.5% Tungsten (W) and/or at least 0.3% Rhenium (Re) and/or at least 0.0015% Boron (B) and especially maximum 0,03wt% Boron (B) .

2. Alloy according to claim 1, comprising (in wt%) : 3.0% to 6.0% of Molybdenum (Mo) and/or Tungsten (W) and/or Rhenium (Re) , especially at most 2.0% Molybdenum (Mo) and/or especially at least 2.0% Tungsten (W) .

3. Alloy according to claim 1 or 2, comprising (in wt%) :

0.02% to 0.3% of Carbon (C) and/or Zirconium (Zr) and/or Boron (B) .

4. Alloy according to any of the claims 1, 2 or 3, comprising (in wt%) :

7.0% to 9.0% Cobalt (Co) , 7.0% to 9.0% Iron (Fe) , 12.0% to 13.5% Chromium (Cr) , 0.7% to 1.3% Molybdenum (Mo) , 3.4% to 4.0% Tungsten (W) , 4.9% to 5.3% Aluminum (Al) , 6.0% to 8.0% Tantalum (Ta) , 0.04% to 0.08% Carbon (C) , 0.005% to 0.015% Zirconium (Zr) , 0.005% to 0.015% Boron (B) , 0.05% to 0.2% Hafnium (Hf ) , 0.005% to 0.05% Silicon (Si) , 0.03% to 0.2% of Yttrium (Y) .

5. Alloy according to claim 4, comprising (in wt%) :

8 .0% Cobalt (Co) , 8.0% Iron ( Fe ) , 12.5% Chromium (Cr) , 1.0% Molybdenum (Mo) , 3.7% Tungsten (W) ,

5.1% Aluminum (Al) , 6.5% Tantalum (Ta) , 0.05% Carbon (C) , 0.01wt% Zirconium (Zr) , 0.1wt% Hafnium (Hf ) , 0.01wt% Silicon (Si) , 0.05wt% Yttrium (Y) .

6. Alloy according to any of the claims 1, 2, 3, comprising (in wt%)

7.0% to 9.0% Cobalt (Co) , 7.0% to 9.0% Iron (Fe) , 13.5% to 16.0% Chromium (Cr) , 0.7% to 1.3% Molybdenum (Mo) , 3.4% to 4.0% Tungsten (W) , 4.2% to 4.8% Aluminum (Al) , 4.0% to 6.0% Tantalum (Ta) , 0.03% to 0.08% Carbon (C) , 0.005% to 0.015% Zirconium (Zr) , 0.005% to 0.015% Boron (B) , 0.05% to 0.2% Hafnium (Hf ) , 0.005% to 0.05% Silicon (Si) , 0.03% to 0.2% of Yttrium (Y) .

7. Alloy according to claim 6, comprising (in wt%) :

8 .0% Cobalt (Co) , 8.0% Iron ( Fe ) , 15.0% Chromium (Cr) , 1.0% Molybdenum (Mo) , 3 .7% Tungsten (W) , 4.5% Aluminum (Al) , 5.0% Tantalum (Ta) , 0.05% Carbon (C) ,

0.01% Zirconium (Zr) , 0.1% Hafnium (Hf ) , 0.01% Silicon (Si) , 0.05% Yttrium (Y) .

8. Alloy according to Claim 6, comprising (in wt%) :

8 .0% Cobalt (Co) , 8.0% Iron ( Fe ) , 15.0% Chromium (Cr) , 1.5% Molybdenum (Mo) , 2.5% Tungsten (W) , 4.5% Aluminum (Al) , 5.0% Tantalum (Ta) , 0.05% Carbon (C) , 0.01% Zirconium (Zr) , 0.1% Hafnium (Hf ) , 0.01% Silicon (Si) , 0.05% Yttrium (Y) .

9. Alloy according to any of the claims 1, 2, 3, comprising (in wt%) :

7.0% to 9.0% Cobalt (Co) , 7.0% to 9.0% Iron (Fe) , 13.5% to 16.0% Chromium (Cr) , 1.2% to 1.8% Molybdenum (Mo) , 2.2% to 2.8% Tungsten (W) , 4.2% to 4.8% Aluminum (Al) , 4.0% to 6.0% Tantalum (Ta) , 0.04% to 0.08% Carbon (C) , 0.005% to 0.015% Zirconium (Zr) , 0.005% to 0.015% Boron (B) , 0.05% to 0.2% Hafnium (Hf ) , 0.005% to 0.05% Silicon (Si) ,

0.03% to 0.2% of Yttrium (Y) .

10. Alloy according to Claim 9, comprising (in wt%) :

11. Alloy according to any of the claims 1, 2, 3, comprising (in wt%)

7.0% to 9.0% Cobalt (Co) , 7.0% to 9.0% Iron (Fe) , 13.5% to 16.0% Chromium (Cr) , 0.7% to 1.7% Molybdenum (Mo) , 2.0% to 4.0% Tungsten (W) , 4.2% to 4.8% Aluminum (Al) , 4.0% to 6.0% Tantalum (Ta) , 0.03% to 0.08% Carbon (C) , 0.005% to 0.015% Zirconium (Zr) , 0.005% to 0.015% Boron (B) , 0.05% to 0.2% Hafnium (Hf ) , 0.005% to 0.05% Silicon (Si) 0.01% to 0.15% of Yttrium (Y) , 0.01% to 0.15% of Lanthanum (La) .

12. Alloy according to claim 11, comprising (in wt%) :

8 .0% Cobalt (Co) , 8.0% Iron ( Fe ) , 15.0% Chromium (Cr) , 1.5% Molybdenum (Mo) , 2.5% Tungsten (W) , 4.5% Aluminum (Al) , 5.0% Tantalum (Ta) , 0.05% Carbon (C) , 0.01% Zirconium (Zr) , 0.1% Hafnium (Hf ) , 0.01% Silicon (Si) , 0.025% Yttrium (Y) , 0.025% Lanthanum (La) .

13. Alloy according to any of the claims 1, 2, 3, comprising (in wt%)

7.0% to 9.0% Cobalt (Co) , 7.0% to 9.0% Iron (Fe) , 13.5% to 16.0% Chromium (Cr) , 0.7% to 1.7% Molybdenum (Mo) , 2.0% to 4.0% Tungsten (W) , 4.2% to 4.8% Aluminum (Al) , 4.0% to 6.0% Tantalum (Ta) , 0.03% to 0.08% Carbon (C) , 0.005% to 0.015% Zirconium (Zr) , 0.005% to 0.015% Boron (B) , 0.05% to 0.2% Hafnium (Hf ) , 0.005% to 0.05% Silicon (Si) , 0.02% to 0.2% of the sum of rare earths such as Scandium (Sc) , Yttrium (Y) , the Actinides and/or the Lanthanides.

14. Powder comprising particles made of the alloy according to any of the previous claims, optionally comprising binder for binder jet printing or abrasive particles for seals.

15. Component made of the alloy according to any of the previous claims 1 to 13.

16. Component, on which material is added by welding, printing using an alloy according to any of the previous claims 1 to 13 or a powder according to claim 13.

17. Component according to claim 15, which is additively manufactured.

18. Component according to claim 15, which is casted using an alloy according to any of the previous claims 1 to 13.

19. Method to produce a component by casting using an alloy according to any of the previous claims 1 to 13.

20. Method to produce a component by additive manufacturing using an alloy according to any of the previous claims 1 to 13.