WO2019077333A1 - Alliage à base de nickel - Google Patents

Alliage à base de nickel Download PDF

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Publication number
WO2019077333A1
WO2019077333A1 PCT/GB2018/052973 GB2018052973W WO2019077333A1 WO 2019077333 A1 WO2019077333 A1 WO 2019077333A1 GB 2018052973 W GB2018052973 W GB 2018052973W WO 2019077333 A1 WO2019077333 A1 WO 2019077333A1
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WIPO (PCT)
Prior art keywords
alloy
nickel
weight percent
composition
tantalum
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PCT/GB2018/052973
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English (en)
Inventor
David Crudden
Roger Charles REED
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Oxmet Technologies Limited
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Application filed by Oxmet Technologies Limited filed Critical Oxmet Technologies Limited
Priority to EP18788879.7A priority Critical patent/EP3697938B1/fr
Priority to JP2020542211A priority patent/JP2020537051A/ja
Publication of WO2019077333A1 publication Critical patent/WO2019077333A1/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C19/00—Alloys based on nickel or cobalt
    • C22C19/03—Alloys based on nickel or cobalt based on nickel
    • C22C19/05—Alloys based on nickel or cobalt based on nickel with chromium
    • C22C19/051—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W
    • C22C19/056—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W with the maximum Cr content being at least 10% but less than 20%
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D5/00—Blades; Blade-carrying members; Heating, heat-insulating, cooling or antivibration means on the blades or the members
    • F01D5/02—Blade-carrying members, e.g. rotors
    • F01D5/06—Rotors for more than one axial stage, e.g. of drum or multiple disc type; Details thereof, e.g. shafts, shaft connections
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2300/00—Materials; Properties thereof
    • F05D2300/10—Metals, alloys or intermetallic compounds
    • F05D2300/17—Alloys
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2300/00—Materials; Properties thereof
    • F05D2300/10—Metals, alloys or intermetallic compounds
    • F05D2300/17—Alloys
    • F05D2300/177—Ni - Si alloys

Definitions

  • the present invention relates to a nickel-based superalloy composition for use as a turbine disc component within a gas turbine engine and other turbomachinery.
  • the turbine disc is a critical component in gas turbine engines. Increases in turbine disc alloy performance - in terms of maximum operating temperature and maximum service - life can have a significant impact on the efficiency of the engine as well as the cost effectiveness of operating the engine.
  • Table 1 Nominal composition in wt.% of commonly applied nickel-based superalloys used for powder metallurgy turbine discs.
  • It is the aim of the present invention is deliver substantially high strength in combination with a reduction in alloy cost and an improvement in oxidation/corrosion resistance.
  • the balance of properties for the new alloy make it more cost effective for the production of components for high temperature applications; in particular for use as a turbine disc application where the operating temperature for the component is 800°C or greater.
  • the present invention provides a nickel-based alloy composition consisting, in weight percent, of: a nickel -based alloy composition consisting, in weight percent, of: between 9.5 and 14.4% chromium, between 3.8 and 9.6% cobalt, between 0.0 and 4.0%) iron, between 0.6 and 5.1% molybdenum, between 0.7 and 6.2% tungsten, between 2.6 and 3.3%> aluminium, between 2.3 and 5.6% titanium , between 0.0 and 4.0% niobium, between 0.0 and 2.4% tantalum, between 0.01 and 0.1%) carbon, between 0.001 and 0.1% boron, between 0.001 and 0.3% zirconium, between 0.0 and 0.5%) silicon, between 0.0 and 0.1% yttrium, between 0.0 and 0.1% lanthanum, between 0.0 and 0.1% cerium, between 0.0 and 0.003%) sulphur, between 0.0 and 0.25% manganese, between 0.0 and 0.5%> vanadium, between 0.0 and 0.5% copper, and between 0.0 and 0.5% ha
  • This alloy provides a good compromise between high strength, cost, oxidation/corrosion resistance and resistance to TCP formation.
  • WNb, WT 3 and Wco are the weight percent of niobium, tantalum and cobalt in the alloy respectively
  • Such alloys are optimised for reduced cost.
  • the following equation is satisfied in which WNb, Wia, W-n and WAI are the weight percent of niobium, tantalum, titanium and aluminium in the alloy respectively
  • WNb, Wia, W-n and WAI are the weight percent of niobium, tantalum, titanium and aluminium in the alloy respectively
  • Such alloys have high ⁇ ' phase stability and resist unwanted eta phase and delta phase. Thus such alloys have good ductility and fatigue resistance.
  • WNb, WT 3 , W-n and WAI are the weight percent of niobium, tantalum, titanium and aluminium in the alloy respectively
  • such alloys have a solvus temperature of the ⁇ ' phase of less than 1180°C allowing heat treatment above the gamma-prime solvus whilst reducing susceptibility of the alloy to cracking on cool down from above the ⁇ ' solvus temperature.
  • WNb, Wia, WTI and WAI are the weight percent of niobium, tantalum, titanium and aluminium in the alloy respectively
  • Such an alloy has good strength properties.
  • Ww and Wia are the weight percent of tungsten and tantalum, in the alloy respectively
  • W w + l.lW Ta ⁇ 6.2 preferably W w + l.lW Ta ⁇ 4.6 most preferably W w + l.lW Ta ⁇ 2.9
  • Such an alloy has limited density whilst maintaining a high strength.
  • Ww, Wco and WMO are the weight percent of tungsten, cobalt and molybdenum, in the alloy respectively
  • Such an alloy has particularly high creep resistance.
  • the nickel-based alloy composition consists of in weight percent, 10.0 wt.% or more chromium, more preferably 1 1.5 wt.% or more chromium. Such an alloys has improved corrosion resistance.
  • the nickel -based alloy composition consists of in weight percent, 5.5 wt.% or more cobalt. Such an alloy has an improved balance of creep resistance and alloy stability.
  • the nickel -based alloy composition consists of, weight percent, 8.1 wt.% or less cobalt, preferably 8.0 wt.% or less cobalt, more preferably 6.0 wt.% or less cobalt. Such an alloy has reduced cost.
  • the nickel-based alloy composition consists of in weight percent, 1.0 wt.% or more iron. Such an alloy has the benefit of being less expensive and is more easily recycled.
  • the nickel-based alloy composition consists of, in weight percent, 2.0 wt.%) or less iron.
  • Such an alloy has improved microstructural stability whilst providing a good balance of low cost and improved recyclability.
  • the nickel-based alloy composition consists of, in weight percent, 2.2 wt.% or more molybdenum, preferably 3.6 wt.% or more molybdenum. Such an alloy has a better balance of creep resistance and density. In an embodiment the nickel-based alloy composition consists of, in weight percent, 4.1 wt.% or less molybdenum. Such an alloy has still further improved alloy stability.
  • the nickel-based alloy composition consists of, in weight percent, 1.9 wt.%) or more tungsten. Such an alloy has an even better balance of creep resistance and alloy stability.
  • the nickel-based alloy composition consists of, in weight percent, 4.6 wt.%) or less tungsten, preferably 2.9 wt.%> or less tungsten. This results in an alloy with an even lower density.
  • the nickel-based alloy composition consists of, in weight percent, 2.6 wt.%) or more aluminium. Such an alloy achieves an improved combination of strength, ⁇ ' solvus and stability of the ⁇ '.
  • the nickel-based alloy composition consists of, in weight percent, 3.0 wt.%) or less aluminium. Such an alloy achieves a ⁇ ' solvus at a lower temperature.
  • the nickel-based alloy composition consists of, in weight percent, 2.6 wt.%) or more titanium, preferably 3.0 wt.%> or more titanium, more preferably 3.5 wt.%> or more titanium, most preferably 4.1 wt.%> or more titanium.
  • Increasing the titanium content enables a reduction in the amount of tantalum needed to provide an alloy of a certain strength and this reduces cost for such an alloy.
  • the nickel -based alloy composition consists of, in weight percent, 1.8 wt.% or less tantalum, preferably 1.0 wt.% or less tantalum. Such an alloy has reduced cost and density.
  • the nickel-based alloy composition consists of, in weight percent, 2.7 wt.%) or less niobium. This achieves an alloy with improved creep properties at reduced cost. In an embodiment the nickel-based alloy composition consists of 51 - 58% volume fraction gamma-prime at 850°C. This achieves an alloy with a high degree of strength in combination with a lower gamma-prime solvus.
  • a turbine disc which is formed of the nickel-based alloy composition of the present invention.
  • a gas turbine engine comprises the turbine disc made from the nickel-based alloy composition of the present invention.
  • Figure 1 shows the calculated trade-off between the elemental cost and yield strength (in terms of strength merit index) for the alloys listed in Table 1 and alloys within the alloy design space listed in Table 2;
  • Figure 2 is a contour plot showing the effect of cobalt and niobium on the elemental cost of alloys when the tantalum content is fixed at 0.0 wt.%;
  • Figure 3 is a contour plot showing the effect of cobalt and niobium on the elemental cost of alloys when the tantalum content is fixed at 1.0 wt.%
  • Figure 4 is a contour plot showing the effect of cobalt and niobium on the elemental cost of alloys when the tantalum content is fixed at 2.0 wt.%;
  • Figure 5 is a contour plot showing the effect of cobalt and niobium on the elemental cost of alloys when the tantalum content is fixed at 3.0 wt.%;
  • Figure 6 is a contour plot showing the effect of cobalt and niobium on the elemental cost of alloys when the tantalum content is fixed at 4.0 wt.%;
  • Figure 7 is a contour plot showing the effect of elements aluminium and titanium on yield strength (in terms of strength merit index), for alloys with the preferred elemental cost ( ⁇ 14.7 $/kg) when the niobium content is fixed at 0.0 wt.% and tantalum content is fixed at 0.0 wt.%.
  • Superimposed is the preferred limits for the ratio of the elements titanium, niobium and aluminium according to the relationship (0.6#3 ⁇ 4+0.31 W3 ⁇ 4b)/ ⁇ Ai;
  • Figure 8 is a contour plot showing the effect of elements aluminium and titanium on yield strength (in terms of strength merit index), for alloys with the preferred elemental cost ( ⁇ 14.7 $/kg) when the niobium content is fixed at 1.0 wt.% and tantalum content is fixed at 0.0 wt.%.
  • Superimposed is the preferred limits for the ratio of the elements titanium, niobium and aluminium according to the relationship (0.6 Wn+0.31 Wm)/WAi;
  • Figure 9 is a contour plot showing the effect of elements aluminium and titanium on yield strength (in terms of strength merit index), for alloys with the preferred elemental cost ( ⁇ 14.7 $/kg) when the niobium content is fixed at 2.0 wt.% and tantalum content is fixed at 0.0 wt.%). Superimposed is the preferred limits for the ratio of the elements titanium, niobium and aluminium according to the relationship W b)/ WA ⁇ ',
  • Figure 10 is a contour plot showing the effect of elements aluminium and titanium on yield strength (in terms of strength merit index), for alloys with the preferred elemental cost ( ⁇ 14.7 $/kg) when the niobium content is fixed at 3.0 wt.% and tantalum content is fixed at 0.0 wt.%).
  • superimposed is the preferred limits for the ratio of the elements titanium, niobium and aluminium according to the relationship (0.6 Wn+0.31 Wm)/WA ⁇ ,'
  • Figure 11 is a contour plot showing the effect of elements aluminium and titanium on yield strength (in terms of strength merit index), for alloys with the preferred elemental cost ( ⁇ 14.7 $/kg) when the niobium content is fixed at 4.0 wt.% and tantalum content is fixed at 0.0 wt.%).
  • superimposed is the preferred limits for the ratio of the elements titanium, niobium and aluminium according to the relationship (0.6 Wn+0.31 Wm /WA ;
  • Figure 12 is a contour plot showing the effect of elements aluminium and niobium plus titanium (according to the relationship 0.6Wn+0.3 Wwb) on ⁇ ' solvus temperature, for alloys with the preferred elemental cost ( ⁇ 14.7 $/kg) when tantalum content is fixed at 0.0 wt.%>.
  • Figure 13 is a contour plot showing the effect of elements aluminium and niobium plus titanium (according to the relationship 0.6Wn+0.3 W b) on volume fraction of ⁇ ' at 900°C, for alloys with the preferred elemental cost ( ⁇ 14.7 $/kg) when tantalum content is fixed at 0.0 wt.%).
  • Figure 14 is a contour plot showing the effect of elements tungsten and tantalum on alloy density
  • Figure 15 is a contour plot showing the effect of elements tungsten and molybdenum on creep resistance (in terms of creep merit index) when the tantalum content is fixed at 0.0 wt.%;
  • Figure 16 is a contour plot showing the effect of elements tungsten and molybdenum on creep resistance (in terms of creep merit index) when the tantalum content is fixed at 1.0 wt.%;
  • Figure 17 is a contour plot showing the effect of elements tungsten and molybdenum on creep resistance (in terms of creep merit index) when the tantalum content is fixed at 2.0 wt.%;
  • Figure 18 is a contour plot showing the effect of elements tungsten and molybdenum on creep resistance (in terms of creep merit index) when the tantalum content is fixed at 3.0 wt.%;
  • Figure 19 is a contour plot showing the effect of elements tungsten and molybdenum on creep resistance (in terms of creep merit index) when the tantalum content is fixed at 4.0 wt.%
  • Figure 20 is a contour plot showing the effect of elements tungsten and molybdenum on creep resistance (in terms of creep merit index) when the tantalum content is fixed at 5.0 wt.%;
  • Figure 21 is a contour plot showing the effect of elements chromium and tungsten plus molybdenum (according to the relationship WMO+0.5WW) on the stability number Md.
  • nickel-based superalloys have been designed through empiricism. Thus their chemical compositions have been isolated using time consuming and expensive experimental development, involving small-scale processing of limited quantities of material and subsequent characterisation of their behaviour.
  • the alloy composition adopted is then the one found to display the best, or most desirable, combination of properties.
  • the large number of possible alloying elements indicates that these alloys are not entirely optimised and that improved alloys are likely to exist.
  • ABS Alloys-By-Design
  • the first step in the design process is the definition of an elemental list along with the associated upper and lower compositional limits.
  • the compositional limits for each of the elemental additions considered in this invention - referred to as the "alloy design space" - are detailed in Table 2.
  • the second step relies upon thermodynamic calculations used to calculate the phase diagram and thermodynamic properties for a specific alloy composition. Often this is referred to as the CALPHAD method (CALculate PHAse Diagram). These calculations are conducted at the typical service temperature for the new alloy (900°C), providing information about the phase equilibrium (microstructure).
  • CALPHAD method CALculate PHAse Diagram
  • a third stage involves isolating alloy compositions which have the desired microstructural architecture.
  • the creep rupture life generally improves as the volume fraction of the precipitate hardening phase ⁇ ' is increased, the most beneficial range for volume fraction of ⁇ ' lies between 60%-70% at 900°C (however often due to other design restraints volume fraction may be limited to lower values than this and so alloys with a ⁇ ' volume fraction of 50% to 60% are included). At values above 70%) volume fraction of ⁇ ' a drop in creep resistance is observed.
  • the lattice misfit ⁇ is defined as the mismatch between ⁇ and ⁇ ' phases, and is determined according to
  • ⁇ ⁇ and ci are the lattice parameters of the ⁇ and ⁇ ' phases.
  • the model isolates all compositions in the design space which are calculated to result in a desired volume fraction of ⁇ ', which have a lattice misfit ⁇ ' of less than a predetermined magnitude.
  • merit indices are estimated for the remaining isolated alloy compositions in the dataset. These include: creep-merit index (which describes an alloy's creep resistance based solely on mean composition), strength-merit index (which describes an alloy's precipitation yield strength based solely on mean composition), density, cost, stable microstructure and gamma-prime solvus temperature.
  • the calculated merit indices are compared with limits for required behaviour, these design constraints are considered to be the boundary conditions to the problem. All compositions which do not fulfil the boundary conditions are excluded. At this stage, the trial dataset will be reduced in size quite markedly.
  • the final, sixth stage involves analysing the dataset of remaining compositions. This can be done in various ways. One can sort through the database for alloys which exhibit maximal values of the merit indices - the lightest, the most creep resistant, the most oxidation resistant, and the cheapest for example. Or alternatively, one can use the database to determine the relative trade-offs in performance which arise from different combination of properties.
  • the six merit indicies are now described.
  • the first merit index is the creep-merit index.
  • time-dependent deformation i.e. creep
  • a nickel-based superalloy occurs by dislocation creep with the initial activity being restricted to the ⁇ phase.
  • the rate-controlling step is then the escape of trapped configurations of dislocations from ⁇ / ⁇ ' interfaces, and it is the dependence of this on local chemistry - in this case composition of the ⁇ phase - which gives rise to a significant influence of alloy composition on creep properties.
  • a physically-based microstructure model can be invoked for the rate of accumulation of creep strain ⁇ when loading is uniaxial and along the (OOl crystallographic direction.
  • the equation set is
  • Equation 3 describes the dislocation multiplication process which needs an estimate of the multiplication parameter C and the initial dislocation density.
  • the term is the effective diffusivity controlling the climb processes at the particle/matrix interfaces.
  • microstructural architecture is assumed constant (microstructural architecture is mostly controlled by heat treatment) so that ⁇ ⁇ is fixed, any dependence upon chemical composition arises through D eS .
  • ⁇ ⁇ 1 'S employed which needs to be maximised, which is given by c reep (4) where , is the atomic fraction of solute / ' in the ⁇ phase and D i is the appropriate interdiffusion coefficient.
  • the second merit index is a strength merit index.
  • M strength a merit index for strength
  • y APB is the anti-phase boundary (APB) energy
  • ⁇ is the volume fraction of the ⁇ ' phase
  • b is the Burgers vector.
  • YAPB I 95 - 1.7x Cr ⁇ 1 x Mo + 4.6x w + 27.1x Ta + 21Ax Nb + 15x Ti (6)
  • xcr, XMO, XW, ⁇ , m and xn represent the concentrations, in atomic percent, of chromium, molybdenum, tungsten, tantalum, niobium and titanium in the ⁇ ' phase, respectively.
  • the composition of the ⁇ ' phase is determined from phase equilibrium calculations.
  • the third merit index is density.
  • the density, p was calculated using a simple rule of mixtures and a correctional factor, where, , is the density for a given element and x, is the atomic fraction of the alloy element.
  • the fourh merit index is cost.
  • x the weight fraction of the alloy element
  • c the current (2017) raw material cost for the alloying element
  • a fifth merit index is based upon rejection of candidate alloys on the basis of unsuitable microstructural architecture made on the basis of susceptibility to TCP phases.
  • Md d-orbital energy levels of the alloying elements
  • a sixth merit index is the gamma-prime solvus temperature.
  • the gamma-prime solvus is defined as the temperature where the volume fraction of gamma-prime tends to zero. This is determined using thermodynamic calculations - as previously described above in the second step of the Alloys-by-Design method. The phase diagram and thermodynamic properties for a specific alloy composition is calculated and used to find the temperature at which this phase transition occurs.
  • the ABD method described above was used to isolate the inventive alloy composition.
  • the design intent for this alloy was to deliver substantially high strengthen in combination with a reduction in alloy cost and an improvement in oxidation/corrosion resistance.
  • the balance of properties for the new alloy make it more cost effective for the production of components for high temperature applications.
  • the material properties - determined using the ABD method - for the nominal compositions of the commonly applied/researched alloys used for powder metallurgy (PM) turbine disc applications, listed in Table 1, are listed in Table 3.
  • the design of the new alloy was considered in relation to the predicted properties listed for these alloys. The rationale for the design of the new alloy is now described.
  • Table 3 Calculated phase fractions, misfit and merit indices made with the "Alloys-by-Design" software. Results for nickel-based superalloys listed in Table 1.
  • Figures 2-6 show the influence of the elements tantalum, cobalt and niobium on alloy cost. These elements have a cost which is substantially higher than the base element nickel and therefore strongly increase the price of the alloy (based on metal September 2017 metal prices).
  • the cost of tantalum, cobalt and niobium normalised to the price of nickel are 11.93, 5.45 and 3.82, respectively.
  • a minimum cobalt level of 3.8 wt.% is desirable to provide the alloy with sufficient creep strength (in terms of creep merit index), described later in relation to Figures 15-20.
  • the cost target for the present invention is less than or equal to 14.7 $/kg; reducing the elemental cost by 10% in comparison to lowest cost alloy listed in Table 1 (Alloy N19, 16.4$/Kg).
  • the maximum tantalum content in the alloy should be 2.4 wt.%, see /(cost) or less.
  • the maximum cobalt content should be limited to 9.6 wt.% in order to achieve the cost target ( Figure 2).
  • the numerical value for /(cost) should be less than or equal to 12.4 to achieve a cost of 14.0 $/kg or less reducing the elemental cost by 15% compared to the lowest cost alloy (Alloy N19, 16.4$/Kg), therefore based on the minimum cobalt concentration (3.8 wt.%) and minimum niobium concentration (0.0 wt.%) it is preferred that the maximum tantalum content in the alloy should be less than or equal to 1.8 wt.%.
  • the maximum cobalt content is preferably limited to less than 8.1 wt.% for cost considerations ( Figure 2).
  • the numerical value for (cost) should be less than or equal to 9.5 to achieve a cost of 13.1 $/kg or less reducing the elemental cost by 20% compared to the lowest cost alloy (Alloy 19, 16.4$/Kg) therefore based on the minimum cobalt concentration (3.8 wt.%) and minimum niobium concentration (0.0 wt.%)it is preferred that the maximum tantalum content in the alloy should be less than or equal to 1.0 wt.%. To achieve a cost of 13.1 $/kg or less it is most preferable that the maximum cobalt content is preferably limited to 6.0 wt.% ( Figure 2).
  • in an embodiment of the invention is desirable to include iron in substitution for nickel content. This has the benefit of reducing alloy cost and increasing the ability for the alloy to be recycled. Additions of iron may result in increased microstructural instability. Limiting iron additions to a level of 4.0 wt.% produces a good balance of low cost, improved recyclability and microstructural stability, more preferably a range between 1.0 wt.% and 2.0 wt.% is desirable.
  • the present invention relates to a high strength alloy.
  • the target for the invention is to have a strength merit index of 1700 MPa or higher.
  • This target for strength merit index provides the alloy with a maximum operating temperature equivalent to the highest strength alloys listed in Table 1 (three highest strength alloys ranging between 1719 -1854MPa), but at substantially reduced elemental cost (between 30-45% compared to alloys with strength merit index greater than ⁇ ).
  • a substantial improvement in the combination of strength and cost is achieved.
  • the main alloying additions used to increase the strength merit index are the gamma- prime ( ⁇ ') forming elements, aluminium, titanium, niobium and tantalum.
  • Figures 7-11 show the influence of the elements aluminium, titanium and niobium on strength for alloys which meet the cost target (note tantalum containing alloys are not included in results, Figures 7-11).
  • the addition of titanium, niobium and tantalum have been given a factor to convert the weight percent addition to an "aluminium equivalent". This allows for direct comparison of the influence of elements which have very different densities.
  • a constant is added to convert the elemental additions of niobium (8.57 g/cm 3 ) and tantalum (16.4 g/cm 3 ) to an "aluminium equivalent", thus, niobium and tantalum have correctional factors (determined from their density relative to aluminium) of 0.3 and 0.15 respectively. From Figures 7-11 a relationship between elemental additions (based upon titanium, aluminium and niobium) and target alloy strength was derived.
  • Tantalum is an optional element present in an amount of 2.4 wt% or less.
  • tantalum can be added up to a level 2.4 wt.% in atomic substitution for titanium and niobium, (that is, for every atom of tantalum added the maximum of allowable level of one or both of titanium and niobium is decreased such that the maximum atomic percent of titanium plus tantalum plus niobium is equal to the atomic percent equivalent of the sum of the maximum allowable levels of titanium and niobium).
  • the numerical value for/(strength) should be greater than or equal to 3.7.
  • the numerical value for (strength) should preferably be greater than or equal to 4.0 or even 4.1.
  • the solvus temperature of the y'phase is less than 1180°C.
  • a ⁇ ' solvus of less than 1180°C is preferred as this allows for heat treatment above the ⁇ ' solvus whilst reducing the susceptibility of the alloy to cracking on cool down from above the ⁇ ' solvus temperature.
  • Heat-treatment above the ⁇ ' solvus temperature is desirable as this enables the growth of coarse grains which improving resistance to dwell fatigue, this damage mechanism is often a life limiting factor in this class of alloys.
  • the value for /(solvus) should be less than 6.3, preferably the numerical value should be less than 5.9 to produce an alloy with a solvus less than 1 170°C which will improve the ability to process the alloy.
  • Niobium must also be limited to less than 4.0 wt.% as high concentrations of niobium stabilise the niobium rich delta phase Ni 3 Nb. Because of its deleterious effect on stability, niobium need not be present in the alloy.
  • tantalum can be added up to a level 2.4 wt.% in substitution for titanium and niobium, in this embodiment the ratio of the elements should adhere to the following relationship (0.6#3 ⁇ 4+0.31 W b+0.15 Wr a WM ⁇ 1.3
  • the minimum level of titanium required is 2.3 wt.% (see equation for /(strength)), preferably titanium is greater than 2.6 wt.% to allow for the preferred tantalum content of 1.8wt.%, more preferably the titanium content is greater than 3.0 wt.% to allow for the more preferable tantalum content (1.0%), most preferably titanium is greater than 3.5 wt.% so that the alloy can be substantially free from tantalum, this provides an improved combination of cost and strength.
  • titanium is greater than 4.1 wt.% as this allows the alloy to be substantially free from tantalum and use the preferred level of niobium (2.7 wt.% or less) which is described later in relation to creep merit index and alloy cost .
  • the aluminium content should be greater than 2.6 wt.% to ensure that a desirable combination of strength, ⁇ ' solvus and stability of the ⁇ ' phase is achieved (i.e. (0.6 Wn+0 1
  • the additions of aluminium, niobium and titanium influence the fraction of the precipitate hardening ⁇ ' phase.
  • a strength merit index to be greater than 1700MPa - determined by the function for /(strength) - and the ratio of the elements (0.6 ⁇ 3 ⁇ 4+0.31 Wm)/W A ⁇ ⁇ 1.3
  • the ⁇ ' fraction in the alloy should range between 51 % and 58% at a temperature of 850°C ( Figure 13).
  • the gamma-prime volume fraction is measured experimentally by the following procedure. After an aging heat treatment at 850°C a section is taken through the material and polished using conventional/standard metallurgical preparation techniques for scanning electron microscopy.
  • the gamma/gamma-prime microstructure should be observable in a scanning electron microscope, particles of diameter 30 ⁇ or lower should be observable.
  • a 10 of images are taken which provide a statistically representative dataset, the images should cover an area of at least 1mm 2 .
  • the 2-dimensional images which reveal the gamma/gamma-prime microstructure should be processed to identify the gamma-prime phase, the area fraction of the gamma-prime phase should be measured.
  • the area fraction of the phase is taken to be the volume fraction of gamma-prime and should lie between 51-58%.
  • ⁇ ( ⁇ ') 0.6W TL + Q31W NB + 0.8W M
  • ⁇ ( ⁇ ') is a numerical value which ranges between 5.4 and 6.0.
  • tantalum can be added up to a level 2.4 wt.% in substitution for titanium and niobium, additions of aluminium, titanium, niobium and tantalum preferably adheres to the following equation
  • Additions of tantalum are made to increase the strength of the alloy - in terms of strength merit index - by increasing ⁇ ' volume fraction and also by increasing the anti-phase boundary energy. Additions of tungsten to the alloy improve creep strength in the alloy - in terms of creep merit index - due to it very slow diffusion in the gamma matrix, strengthening is also increase by solid solution strengthening the gamma matrix phase.
  • the elements tungsten and tantalum are the heaviest, with a density substantially greater than nickel. Therefore their contribution to strength must be balanced against their negative impact upon alloy density.
  • the density target for the present invention is less than 8.4 g/cm 3 , making it lighter than other alloys with a strength merit index of greater than 1700MPa (Table 3).
  • the numerical value for ⁇ density is less than 4.6 as this produces and alloy with a density of 8.3 g/cm 3 or less, even more preferably the numerical value for (density) is less than 2.9 as this produces and alloy with a density of less than 8.2 g/cm 3 .
  • tungsten is less than or equal to 4.6 wt.%, more preferably less than 2.9 wt.%.
  • a target for creep merit index of 2.4 x 10 "15 m "2 s or greater is required for the alloy, to provide creep strength equivalent to AlloyN19 at areduced cost.
  • the target density of 8.4g/cm 3 or less means tungsten is limited to less than 6.2 wt.% ( Figure 14).
  • Figures 15-20 The role of tungsten, cobalt and molybdenum is demonstrated in Figures 15-20. From Figures 15-20 a relationship between elemental additions (based upon cobalt, molybdenum and tungsten) and target alloy creep merit index was derived. The relationship - which describes a 3 -dimensional surface - was determined in the following way. A relationship between alloy creep merit index and cobalt and tungsten was determined from Figures 15-20 for the creep merit index target of 2.4 x 10 " 15 m "2 s , this was determined for the contour lines for these values. The translation of the line as a function of different molybdenum contents was determined from Figures 15-20.
  • tungsten is limited to 4.6 wt.% to lower alloy density therefore it is preferable to increase molybdenum to 2.2 wt.% or greater. Even more preferable tungsten is limited to 4.6 wt.% and cobalt is less than 8.1 wt.% to reduce both alloy density and cost, therefore it is preferable that that molybdenum is greater than 3.6 wt.%).
  • the maximum molybdenum content limited to less than 5.1 wt.% due to stability requirements, explain later with reference to Figure 21.
  • a minimum tungsten content of 0.7 wt.% is required at maximum cobalt of 9.6 wt.% to achieve the minimum creep merit index of 2.4 x 10 "15 m "2 s, Figure 20.
  • molybdenum is limited to 4.1% for improved alloy stability (see below), thus a tungsten content of greater than 1.9 wt.% is preferred as this results in a better balance of creep resistance and alloy stability.
  • tungsten is limited to 4.6 wt.%, resulting in a preferred cobalt level of 5.5 wt.% or more, even more preferably the tungsten content is limited to 2.9 wt.%) therefore a cobalt content of 8.0 wt.% or greater is preferable (Figure 20) for balance of creep resistance and alloy stability. Based upon the preferred cobalt content of 8.0 wt.% or greater for an improved balance of creep resistance and density it is preferred that niobium is limited to less than 2.7 wt.%> ( Figure 2).
  • Figure 21 describes the effect of chromium content and the sum of the elements molybdenum and tungsten (according to the relationship Mo+0.5W) on the stability number.
  • a higher stability number results in an alloy which is more prone to TCP phase formation.
  • Limiting or stopping the precipitation of TCP phase formation is beneficial as these phases lead to deterioration in material properties.
  • the correctional factor of 0.5 is applied to tungsten as it has a density approximately twice that of molybdenum, this factor accounts for the substantial difference in density of the elements.
  • a chromium level of greater than 9.5 wt.% is desirable in order to achieve a good level of oxidation resistance.
  • the minimum sum of molybdenum and tungsten according to the relation (Mo+0.5W) is 3.7 wt.% (maximum tungsten content of 6.1 wt.% and minimum molybdenum content of 0.6 wt.%). Therefore maximum chromium level must be 14.4 wt.%.
  • the chromium content is greater than 10.0% as this gives an improvement in oxidation resistance.
  • Carbon is added to act as a grain boundary pinning particle, this is necessary when heat treatment is conducted above the gamma-prime solvus temperature to inhibit excessive grain growth.
  • the carbon concentrations should range between 0.01 wt.% and 0.1 wt.%.
  • the levels of carbon are between 0.2 and 0.06, this range provides a better distribution of carbide phases for controlling alloy microstructure, in particular grain size.
  • the boron concentration should range between 0.001 and 0.1 wt.%.
  • the addition of boron can improve creep ductility and grain boundary strength through the formation of boride phases.
  • the boron content in the alloy is between 0.01 and 0.05 wt.%, as this provides a desirable level of the boride phase.
  • the zirconium concentrations should range between 0.001 wt.% and 0.3 wt.%, preferably between 0.02 and 0.1 wt.%.
  • Zirconium plays a role in guttering unwanted impurities in the ally, for example, oxygen and sulphur. These impurities may lead to embrittlement of the alloy particularly due to grain boundary embrittlement. It is beneficial that when the alloy is produced, it is substantially free from incidental impurities.
  • These impurities may include the elements sulphur (S), manganese (Mn) and copper (Cu).
  • the element sulphur should remain below 0.003 wt.% (30 PPM in terms of mass).
  • Manganese is an incidental impurity which is limited to 0.25 wt.%, preferably this limited to less than 0.1 wt.%.
  • Copper (Cu) is an incidental impurity which is preferably limited to 0.5 wt.%.
  • Sulphur above 0.003 wt.%, can lead to embrittlement of the alloy and sulphur also segregates to alloy/oxide interfaces formed during oxidation, preferably sulphur levels of less than less than 0.001 wt.%.
  • Vanadium is an incidental impurity, vanadium negatively influences the oxidation behaviour of the alloy and is which is preferably limited to 0.5 wt.%, preferably less than 0.3 wt.% and most preferably this limited to less than 0.1 wt.%. This segregation may lead to increased spallation of protective oxide scales. If the concentrations of these incidental impurities exceed the specified levels, issues surrounding product yield and deterioration of the material properties of the alloy is expected.
  • hafnium additives of hafnium (Hf) of up to 0.5wt.%, are beneficial for tying up incidental impurities in the alloy and also for providing strength.
  • Hafnium is a strong carbide former it can provide additional grain boundary strengthening. More preferably hafnium is limited to 0.2wt.%, more preferably less than 0.1 wt.% as the elemental cost is significant, additions have a negative impact on alloy cost.
  • Additions of the so called 'reactive-elements', Yttrium(Y), Lanthanum (La) and Cerium (Ce) may be beneficial up to levels of 0.1 wt.% to improve the adhesion of protective oxide layers, such as Cr 2 0 3 .
  • These reactive elements can 'mop-up' tramp elements, for example sulphur, which segregates to the alloy oxide interface weakening the bond between oxide and substrate leading to oxide spallation.
  • Additions of Silicon (Si) up to 0.5 wt.%) may be beneficial, it has been shown that additions of silicon to nickel based superalloys at levels up to 0.5 wt.% are beneficial for oxidation properties. In particular silicon segregates to the alloy/oxide interface and improves cohesion of the oxide to the substrate. This reduces spallation of the oxide, hence, improving oxidation resistance.
  • Table 4 Compositional range in wt. % for the newly design alloy.
  • Example LCPM-1 An example of the composition invention (Example LCPM-1) is listed in Table 5.
  • the alloy listed has a number of benefits in comparison to the high strength alloys listed in Table 1 with a strength merit index greater than or equal to 1700MPa (Table 3).
  • the cost is substantially lower ($14.5 $/kg) in comparison to these alloys with cost between (21.6-28.6 $/kg), providing at least a 32% reduction in elemental cost whilst maintaining an equivalent strength.
  • the LCPM alloy is also of lower density 8.3 g/cm 3 in comparison to these alloys with density ranging between 8.5-8.7 g/cm 3 .
  • the LCPM alloy has a similar chromium content (11.8 wt.%) equivalent to the these alloys which range between 10.0-13.4 wt.%.
  • Table 5 the ratio of the elements according to the relationship
  • Example alloy LCPM-1 is modified in order to achieve and alloy with a lower cost. Cobalt is removed for the alloy to reduce alloy cost. As cobalt provides creep resistance to the alloy substitution of cobalt using molybdenum and tungsten is required, according to the relationship defined for (creep). To manage alloy stability, according to the relationship for (stability) chromium is reduced as molybdenum and tungsten0 levels are increased.
  • the alloys LCPM 6-8 are beneficial when a there is a stronger preference for reduced alloy cost and a less strong preference for lower alloy density (Table 8) and better alloy corrosion resistance (i.e. chromium levels are reduced)
  • Table 7 Example compositions where the chromium, cobalt, molybdenum and tungsten content have been modified in example alloy LCPM-1 to maintain alloy creep resistance at a lower cost.
  • example alloy LCPM-7 is modified to include the optional element tantalum. It is demonstrated that tantalum can be substituted for titanium (LCPM 13-14) and niobium (LCPM 15-18). It is seen that when tantalum is added in atomic substitution for titanium or niobium there is an increase in alloy cost. The addition of tantalum as demonstrated by the examples is beneficial when an increase in alloy strength is preferred over a reduction of alloy cost.
  • Table 9 Example compositions where the niobium, titanium and tantalum content have been modified in example alloy LCPM-7.
  • Table 10 Calculated phase fractions and merit indices made with the "Alloys-by-Design " software. Results for compositions where niobium, titanium and tantalum content have been modified in example alloy LCPM-7 (Table 9).
  • Table 11 Example compositions where the chromium, molybdenum and tungsten content have been modified in example alloy LCPM-1 to adjust the balance between creep resistance and corrosion resistance.
  • Table 12 Calculated phase fractions and merit indices made with the "Alloys-by-Design " software. Results for compositions where the chromium, molybdenum and tungsten content have been modified in example alloy LCPM-1 to adjust the balance between creep resistance and corrosion resistance

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Abstract

La présente invention concerne une composition d'alliage à base de nickel constituée, en pourcentage en poids, de : entre 9,5 et 14.4 % de chrome, entre 3,8 et 9,6 % de cobalt, entre 0,0 et 4,0 % de fer, entre 0,6 et 5,1 % de molybdène, entre 0,7 et 6,2 % de tungstène, entre 2,6 et 3,3 % d'aluminium, entre 2,3 et 5,6 % de titane, entre 0,0 et 4,0 % de niobium, entre 0,0 et 2,4 % de tantale, entre 0,01 et 0,1 % de carbone, entre 0,001 et 0,1 % de bore, entre 0,001 et 0,3 % de zirconium, entre 0,0 et 0,5 % de silicium, entre 0,0 et 0,1 % d'yttrium, entre 0,0 et 0,1 % de lanthane, entre 0,0 et 0,1 % de cérium, entre 0,0 et 0,003 % de souffre, entre 0,0 et 0,25 % de manganèse, entre 0,0 et 0,5 %> de vanadium, entre 0,0 et 0,5 % de cuivre, et entre 0,0 et 0,5 % d'hafnium, le complément étant constitué par le nickel et les impuretés inévitables, sachant que l'équation suivante est satisfaite lorsque W Nb >, W Ta , WTi et WAI correspondent au pourcentage en poids de niobium, de tantale, de titane et d'aluminium dans l'alliage, respectivement : 0,6WTi + 031W Nb + 0,27W Ta + 0,12WAI≥ 3,7.
PCT/GB2018/052973 2017-10-16 2018-10-16 Alliage à base de nickel WO2019077333A1 (fr)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3862448A1 (fr) * 2020-02-07 2021-08-11 General Electric Company Superalliages à base de nickel

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2020086971A1 (fr) 2018-10-26 2020-04-30 Oerlikon Metco (Us) Inc. Alliages à base de nickel résistants à la corrosion et à l'usure

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6231692B1 (en) * 1999-01-28 2001-05-15 Howmet Research Corporation Nickel base superalloy with improved machinability and method of making thereof
US20100008778A1 (en) * 2007-12-13 2010-01-14 Patrick D Keith Monolithic and bi-metallic turbine blade dampers and method of manufacture
US20140314618A1 (en) * 2013-04-23 2014-10-23 General Electric Company Cast nickel-base alloys including iron
WO2015181549A1 (fr) * 2014-05-28 2015-12-03 The University Of Manchester Couche d'accrochage

Family Cites Families (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3619182A (en) * 1968-05-31 1971-11-09 Int Nickel Co Cast nickel-base alloy
US3902862A (en) * 1972-09-11 1975-09-02 Crucible Inc Nickel-base superalloy articles and method for producing the same
GB1511562A (en) * 1974-07-17 1978-05-24 Gen Electric Nickel-base alloys
US6416596B1 (en) * 1974-07-17 2002-07-09 The General Electric Company Cast nickel-base alloy
JPH0339434A (ja) * 1989-07-05 1991-02-20 General Electric Co <Ge> 耐疲れ亀裂性ニッケル基超合金の製造方法およびその製品
JP4449337B2 (ja) * 2003-05-09 2010-04-14 株式会社日立製作所 高耐酸化性Ｎｉ基超合金鋳造物及びガスタービン部品
JP5063550B2 (ja) * 2008-09-30 2012-10-31 株式会社日立製作所 ニッケル基合金及びそれを用いたガスタービン翼
CN101974708A (zh) * 2010-11-05 2011-02-16 钢铁研究总院 一种抗热蚀定向凝固镍基铸造高温合金
US20120282086A1 (en) * 2011-05-04 2012-11-08 General Electric Company Nickel-base alloy
JP5597598B2 (ja) * 2011-06-10 2014-10-01 株式会社日立製作所 Ｎｉ基超合金と、それを用いたガスタービンのタービン動・静翼
JP2014047389A (ja) * 2012-08-31 2014-03-17 Hitachi Ltd 発電用ガスタービン用動翼と、熱処理方法

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6231692B1 (en) * 1999-01-28 2001-05-15 Howmet Research Corporation Nickel base superalloy with improved machinability and method of making thereof
US20100008778A1 (en) * 2007-12-13 2010-01-14 Patrick D Keith Monolithic and bi-metallic turbine blade dampers and method of manufacture
US20140314618A1 (en) * 2013-04-23 2014-10-23 General Electric Company Cast nickel-base alloys including iron
WO2015181549A1 (fr) * 2014-05-28 2015-12-03 The University Of Manchester Couche d'accrochage

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3862448A1 (fr) * 2020-02-07 2021-08-11 General Electric Company Superalliages à base de nickel
US11384414B2 (en) 2020-02-07 2022-07-12 General Electric Company Nickel-based superalloys

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EP3697938A1 (fr) 2020-08-26
GB2567492A (en) 2019-04-17

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