Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C14/00—Alloys based on titanium
• • 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
  • F01D25/00—Component parts, details, or accessories, not provided for in, or of interest apart from, other groups
  • F01D25/005—Selecting particular materials
• • 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
  • F01D5/005—Repairing methods or devices
• • 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
  • F01D5/12—Blades
  • F01D5/28—Selecting particular materials; Particular measures relating thereto; Measures against erosion or corrosion
• • 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
  • F05D2230/00—Manufacture
  • F05D2230/72—Maintenance
• • 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
  • F05D2230/00—Manufacture
  • F05D2230/80—Repairing, retrofitting or upgrading methods
• • 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
  • F05D2300/13—Refractory metals, i.e. Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W
  • F05D2300/133—Titanium
• • 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
  • F05D2300/174—Titanium alloys, e.g. TiAl

Definitions

• the materials constituting the propulsion systems must have, in addition to good resistance to temperature, sufficient mechanical characteristics for application in propulsion systems, and in particular aeronautical turbomachines, particularly in terms of mechanical resistance, oxidation resistance and fatigue resistance.
• titanium alloys are known for the manufacture of compressor disks, compressor blades, compressor impellers or turbomachine nozzles.
• titanium alloys for disks, blades, impellers or turbomachine nozzles have undergone significant changes in chemical composition, with the aim in particular of improving their mechanical resistance at temperature and their resistance to the environment in which these alloys are used.
• the complexity of the chemistry of these alloys can lead to a destabilization of their optimal microstructure, so that the choice of addition elements and their contents is not trivial.
• titanium alloys are competitive compared to steels or nickel-based superalloys at temperatures below 550°C.
• An increase in the operating temperatures of turbomachines requires an increase in their resistance to temperature, particularly with respect to commercial titanium alloys.
• the titanium alloys most used in the aeronautical field are so-called “quasi-o” alloys comprising a very large fraction of the compact hexagonal phase a and the latter generally have good temperature resistance.
• the Ti-6AI-2Sn-4Zr-2Mo alloy is a representative of this family.
• these alloys are sensitive to fatigue called “fatigue with holding time” (or “dwell fatigue” according to the term used in English). This fatigue can be described as a type of fatigue close to creep observed from ambient temperature involving a holding phase of several minutes under stress.
• the invention aims precisely to meet this need, and for this purpose proposes alloys with compositions optimized to present dwell fatigue resistance, corrosion resistance and mechanical strength compatible with use in an aeronautical turbomachine at operating temperatures up to 650°C.
• the invention relates to a titanium alloy comprising, in mass contents:
• Aleq [AI]+[Sn ]/3+[Zr]/6+10*[O]
• [Al], [Sn], [Zr] and [O] are the mass contents in the alloy respectively of aluminum, tin, zirconium and oxygen.
• iron, chromium and nickel reduce the creep resistance of the alloy.
• the inventors have noted that the mass content of equivalent aluminum less than or equal to 8.5%, or even less than or equal to 8.0%, makes it possible to limit the fraction of the o 2 phase in the alloy.
• the significant fraction of o 2 phase which can appear for alloys whose equivalent aluminum mass contents are higher than those described is responsible for undesirable weakening of the alloy.
• alloys whose mass content of equivalent aluminum is greater it has been observed that the transformation kinetics of the a phase will be too high, leading to an increased sensitivity of the alloy to dwell fatigue, which the alloys of the invention aim precisely to avoid.
• the inventors managed on the one hand to identify the importance of the criterion of the mass content of equivalent aluminum as an important criterion for the phenomena present, and on the other hand to propose an optimization of this, by precisely adjusting the content of other elements to meet the technical specifications of an alloy usable in an aeronautical turbomachine whose operating temperature would be at least 550 °C.
• the mass content of equivalent aluminum can be between 6.5% and 8.5%, or even between 6.5% and 8.0%.
• the alloy of the invention comprises an aluminum mass content of between 4.0% and 4.8%, or even between 4.0% and 4.7%.
• the alloy of the invention comprises a molybdenum content by weight of between 4.50% and 5.25%.
• Molybdenum stabilizes the P phase of the alloy, and contributes to solid solution reinforcement.
• the P phase contributes to increasing the ductility of the alloy, and therefore its shaping capacity.
• the silicon mass content of the alloy can be between 0.1% and 0.15%.
• silicon contributes to solid solution reinforcement, and to the formation of silicides, in particular silicides with stoichiometries MsSi and M 5 Si3 where M represents another element, for example titanium, zirconium, molybdenum, niobium.
• MsSi and M 5 Si3 where M represents another element, for example titanium, zirconium, molybdenum, niobium.
• the zirconium mass content may be between 1.0% and 2.0%.
• Zirconium tends to improve the oxidation resistance of the alloy. Excessive additions of zirconium, however, stabilize phase 02, too large a fraction of which reduces the ductility of the alloy and the proposed values are optimums found between the two effects.
• the invention relates to a turbomachine part comprising an alloy as just described.
• Comparative alloy 2 corresponds to the so-called Ti6246 alloy.
• the comparative alloy 3, comp3 corresponds to the so-called IMI-834 alloy, for example commercially available under the commercial reference TIMETAL® 834 from TIMET.
• the inventors first determined the density of the different alloys.
• the density was determined by a law of mixtures weighting the density of each element by its mass content, the whole being reduced by 2.5%.
• the density of an alloy p can be written according to the formula below in which Wi is the mass percentage of the element i and Pi its density.
• the different alloys have densities comparable to those of the alloys and often even lower.
• a second element of comparison of the alloys according to the invention to the alloys of the prior art is their parabolic oxidation constant at 650 ° C denoted k p .
• This constant quantifies the oxidation kinetics of an alloy (mass gain). The higher it is, the more quickly the surface oxide forms, or equivalently, the more quickly the oxygen diffuses within the alloy. This parameter is therefore desired to be as low as possible, for the targeted applications.
• Table 3 lists the parabolic oxidation constants for the examples and comparative examples.
• the constants k p are obtained by a regression model based on the collection and use of experimental data.
• Table 3 illustrates that the alloys of the invention have better resistance to oxidation at 650 ° C than the comparative examples compl and comp2. In addition, it can be noted that the values are at least comparable to the third comparative example which is the one presenting the best resistance to oxidation.
• the alloys according to the invention are further compared to the comparative examples for their mechanical characteristics at room temperature and temperature.
• Table 4 illustrates that the alloys according to the invention have mechanical resistances at room temperature and in temperature at least of the same order as those of the alloys of the prior art.
• the transus temperature P characterizes the stability domain of phase 0. The lower the transus temperature P, the more stable the domain P.
• Table 5 also includes a column indicating the content of phase 02 at equilibrium at 650°C.
• phase 02 If a zero content of phase 02 is desirable, a low content is however not prohibited, because it has been observed that this phase contributes to strengthening by precipitation.
• Table 5 also includes the silicide content.
• the presence of silicides in the alloy ensures a certain strengthening by precipitation which is desirable, and which is also observed for all of the alloys according to the invention.
• Table 5 describes the slope of fraction a at transus 0. This value is an indicator of the kinetics of transformation of the P phase upon cooling. It has been observed that a value that is too large (in absolute value) is associated with an alloy in which the precipitates have a morphology increasing the sensitivity of the alloy to dwell fatigue.
• the compl and comp3 alloys are known to be sensitive to this fatigue mode and have a relatively high slope value a at the transus P (in absolute value).
• the comp2 alloy is much less subject to dwell fatigue. Since the values of the alloys according to the invention are relatively close to the slope value of the comp2 alloy, and in any case much lower (in absolute value) than the values of the compl or comp3 alloys, it is expected that the alloys according to the The invention has good resistance to dwell fatigue.
• the alloys of the invention make it possible to have acceptable behavior for each of the important quantities described above, and in particular: - their oxidation behavior is more acceptable than that of the compl and comp2 alloys of the prior art, as evidenced by the parabolic oxidation constants kp which are much lower than those of the compl and comp2 alloys;

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Turbine Rotor Nozzle Sealing (AREA)
• Powder Metallurgy (AREA)
• Manufacture Of Metal Powder And Suspensions Thereof (AREA)

Applications Claiming Priority (2)

Publications (1)

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• 2022
  • 2022-06-03 FR FR2205372A patent/FR3136241B1/fr active Active
• 2023
  • 2023-06-01 WO PCT/FR2023/050772 patent/WO2023233114A1/fr not_active Ceased
  • 2023-06-01 CA CA3258057A patent/CA3258057A1/fr active Pending
  • 2023-06-01 JP JP2024571181A patent/JP2025520180A/ja active Pending
  • 2023-06-01 US US18/871,244 patent/US20250163545A1/en active Pending
  • 2023-06-01 CN CN202380044683.8A patent/CN119365619B/zh active Active
  • 2023-06-01 EP EP23731333.3A patent/EP4532783A1/fr active Pending

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