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
  • C22C19/057—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W with the maximum Cr content being less 10%
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/10—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of nickel or cobalt or alloys based thereon

Definitions

• the application belongs to the technical field of superalloys and relates to a superalloy with good long-term stability and suitable heat treatments.
• the present application aims to solve some of the technical problems in the related art at least to a certain extent.
• Embodiments of the present application propose a superalloy with good long-term stability.
• This superalloy with good long-term stability not only has excellent mechanical properties, but also has long-term stability and long-lasting life. It fully meets the requirements for the design and use of advanced aero-engines and gas turbines and is suitable for medium- and long-term service parts such as turbine blades, hot-end components of aero-engines and gas turbines.
• the superalloy with good long-term stability comprises (in wt%): C: 0.05% - 0.16%, Cr: 8.0% - 9.5%, Co: 9.0% - 10.5%, W: 9.0% - 10.5%, Mo: 0.2% ⁇ 1.0%, Ta: 2.5% - 3.5%, Al: 5.0% - 6.0%, Ti: 0.5% - 1.5 %, B: 0.01% - 0.025%, Hf: 1.0% - 2.0%; Zr: 0.004% - 0.06%, Nickel (Ni) and inevitable impurities.
• Nickel is especially used for balancing.
• the superalloys according to the embodiments of the present application have good long-term stability.
• the strengthening element design scheme of high Al, low Ti, and high Ta is adopted.
• the superalloy according to the embodiment of the present application comprises: C: 0.06% to 0.09%, Cr: 8.0% - 8.5%, Co: 9.0% - 9.5%, W: 9.1% - 9.8%, Mo: 0.3% - 0.7%, Ta: 3.0% - 3.5%, Al: 5.3% - 5.8%, Ti: 0.5% - 1.0%, B: 0.01% - 0.02%, Hf: 1.1% - 1.7%, Zr: 0.005% - 0.02%.
• Nickel is especially used for balancing.
• each main element in the superalloy of the embodiment of the present application is as follows: Carbon: C mainly suppresses the growth of austenite grains during heating by forming MC-type carbides at the end of solidification in nickel-based superalloys and forms MC along grain boundaries during heat treatment. Various types of carbides, which play a role in strengthening grain boundaries, delaying the initiation, expansion and merging of microcracks, thereby improving the high-temperature durable life of the alloy. When the C content is less than 0.05%, it is not enough to form enough MC. When the C content is too high, the size of MC formed is larger, and it will consume too much Mo, Cr, Ti and Ta in the alloy.
• Ni 3 (Al, Ti) and Ni 3 The Ti and Ta of the (Al, Ti, Ta) composite strengthening phase will be reduced, which will adversely affect the high temperature performance and durability of the alloy, so C should be controlled within 0.05% and 0.16%.
• Chromium Cr The main function of Cr is to improve the oxidation resistance of the alloy and has a certain solid solution strengthening effect. After aging treatment, it can also combine with C to form granular MC distributed along the grain boundaries and plays a role in strengthening the grain boundaries.
• Cr content is too high, it is easy to form the TCP phase, which reduces the long-term microstructure and performance stability of the alloy. Therefore, its content generally does not exceed 25%.
• the Cr content is controlled at 8.0% - 9.5%.
• Co is both an important solid solution strengthening element and an important precipitation strengthening element.
• Co element can be dissolved in the matrix to provide a good solid solution strengthening effect for the alloy, which can significantly reduce the stacking fault energy of the matrix, widen and expand the dislocation width, so that the dislocation is not easy to bunch up and cross-slip occurs, thereby improving the alloy. creep resistance and longevity.
• Co can also partially replace Ni 3 Al-type precipitation of elements in the strengthening phase improves the stability of the phase in long-term service; Co can also reduce the solid solubility of Al and Ti elements in the matrix, promote the precipitation of ⁇ ' strengthening phase and increase the number of precipitation and solid solution.
• temperature When the Co content is lower than 9%, the high temperature strength is low.
• the Co content is higher than 11%, it is easy to form an ⁇ phase that affects its performance in long-term service, so the Co content is controlled at 9.0% - 10.5%.
• W and Mo are one of the main solid-solution strengthening elements, which can be solid-dissolved in the alloy matrix and in the ⁇ ' strengthening phase and at the same time can improve the bonding force between atoms, increase the diffusion activation energy and recrystallization temperature, so as to effectively improve the high temperature strength.
• Mo is too high, long-term high temperature aging is easy to generate ⁇ phase and reduce alloy toughness. Therefore, the Mo content is controlled at 0.2% - 1.0%.
• the atomic radius of W is relatively large, more than ten percent larger than the atomic radius of nickel, and the solid solution strengthening effect is obvious.
• W is an element that accelerates high-temperature corrosion, and will form a harmful delta phase during long-term service, reducing the strength and toughness of the alloy.
• the W content is controlled at 9.0% - 10.5%.
• Aluminum, Titanium and Tantalum Al, Ti and Ta: The three are the forming elements of the strengthening phase ⁇ ' in nickel-based alloys. It is generally believed that with the increase of the content of the three, the amount of ⁇ ' increases, and the high-temperature creep and durability improve, but too much ⁇ ' will cause Deterioration of processability.
• Ti and Ta will also combine with C to form MC-type carbides, which hinder the growth of grain boundaries and the sliding of grain boundaries at high temperatures and play a role in improving high-temperature mechanical properties, but too much Ti and Ta will form large-grained MC-type carbides. Carbides are detrimental to the mechanical properties of the alloy.
• the high-temperature mechanical properties of the alloy depend not only on the amount of ⁇ ' phase, but also on its composition and characteristics. optimization, the best ⁇ ' strengthening effect can be obtained.
• the strengthening element design scheme of high Al, low Ti and high Ta is adopted. 3 (Al, Ti) strengthening phase was modified to form Ni with higher Al content and Ta at the same time 3 (Al, Ti, Ta), compared to conventional Ni 3
• the (Al, Ti) strengthening phase is more resistant to high temperatures, thereby improving the tensile properties and long-lasting life of the alloy.
• the specific control range of the three is: Al: 5.0% - 6.0%, Ti: 0.5% - 1.5%, Ta: 2.5% - 3.5%.
• B The role of B is mainly manifested in two aspects. First, because the atomic radius of B is very small, so B atoms are easily enriched at the grain boundaries. The low melting point elements cannot segregate at the grain boundary, which improves the bonding force of the grain boundary; the second is that the boride on the grain boundary can prevent the grain boundary from slipping, the initiation and expansion of voids, and improve the creep resistance and lasting life of the alloy. favorable. However, too much B will deteriorate the hot workability and welding performance of the alloy, so the suitable B content of the alloy in the embodiment of the present application is 0.01% - 0.025%.
• Zirconium helps to purify the grain boundary and enhance the bonding force of the grain boundary.
• the compound addition of Zr and B helps to maintain the high temperature strength and long-lasting life of the alloy, but excessive Zr easily reduces the processing performance.
• the alloys in the examples of this application control Zr at 0.004% - 0.06%.
• Mg, Mn, Si, Fe the superalloy is micro-alloyed with Mg, Mn, Si and/or Fe.
• Fe is quite close in the PSE (Periodic system of the elements) to Ni and next to Co. Mn is next to Fe in the PSE. Therefore, these elements Fe, Mn should be controlled.
• Si is next to Al in the PSE and should be controlled, too.
• Mg, Mn, Si, Fe as well as B, C atoms are segregated at grain boundaries, and this segregation is a balanced segregation.
• the segregation of these atoms at the grain boundary improves the bonding force of the grain boundary and increases the strength of the grain boundary.
• Mg, Mn, Fe atoms are not only segregated at grain boundaries, but also at carbide phase boundaries, ⁇ ' phase boundaries. Mg atoms also enter into ⁇ ' and carbides, which have a favorable effect on the mechanical properties.
• the segregation of a small amount of Mg, Mn, Fe at the grain boundary reduces the grain boundary energy and phase boundary energy, and improves and refines the morphology of other grain boundary precipitation phases at the grain boundary carbide level.
• carbides can be lumped or spheroidized, effectively inhibiting grain boundary sliding, reducing grain boundary stress concentration, and eliminating notch sensitivity.
• Mg, Mn, Fe and Sulfur and other harmful impurities form high melting point compounds such as MgS, which purifies the grain boundary, so that the concentration of S, O, P and other impurity elements in the grain boundary is significantly reduced, and the harmful effects of S, O, P and other impurities are reduced.
• a small amount of Mg, Mn, Fe increases durability and plasticity, improves creep properties and high-temperature tensile plasticity, increases impact toughness and fatigue strength, and can also improve hot workability and yield for some alloys. But the content should not be too high, too high will deteriorate the performance.
• Purity of bar or billets of the superalloy are achieved by carefully choosing the raw material of the alloying elements. Some of the raw material comprises all microalloying elements, some raw material only a part of them.
• Mg Magnesium
• Mn Manganese
• Si Silicon
• Fe Iron
• B Boron
• C Carbon
• Amounts of this microalloying elements are preferably chosen by:
• impurities Sn, Sb, As, Zn, Hg, U, Th, Ce, Ge, Y, Pt, Au, In, Na, K, La, Ce, Pd, Ba
• the unavoidable impurities like Phosphorus (P), Sulfur (S), Copper (Cu), Niobium (Nb), Lead (Pb), Selenium (Se), Wismut (Bi), Tellurium (Te), Thallium (Tl), Nitrogen (N), Oxygen (O), Silver (Ag), Vanadium (V), Gallium (Ga), Rhenium (Re), Ruthenium (Ru) are very small, usually below 0.01%, 0.001% or 0.001% or below, or even undetectable.
• V ⁇ 500ppm and/or Nb ⁇ 500ppm and/or Cu ⁇ 100ppm Preferably is V ⁇ 500ppm and/or Nb ⁇ 500ppm and/or Cu ⁇ 100ppm.
• V 20ppm ⁇ V ⁇ 200ppm and/or Nb ⁇ 50ppm and/or Cu ⁇ 50ppm.
• the alloy can also only reveal his best properties with an appropriate heat treatment.
• a heat treatment is preferably performed at four different temperatures levels
• Each temperature level is characterized by increasing the temperature to his desired temperature, holding time and decreasing the temperature, especially near or to room temperature.
• Active cooling can or must be performed depending on the height of the temperature.
• the solution temperature is depending on the actual composition, but for this claimed small ranges of the inventive superalloy this solution temperature will between 1220°C and 1250°C.
• a stabilization treatment is performed at a temperature which is at least 130°C, especially at least 140°C lower than the solution treatment temperature.
• the difference should not bigger than 250°C, especially not bigger than 200°C.
• this difference is not bigger than 190°C.
• Holding time (preferably 100min to 140min) at the stabilization temperature level for the stabilization treatment is least 40% smaller than the holding time at the first temperature level (preferably 220min to 260min) which is the solution treatment temperature.
• an aging treatment is performed at a temperature which is at least 170°C, especially 180°C lower than the temperature of the stabilization treatment temperature. But preferably this difference is not bigger than 250°C.
• another level can be performed as an intermediate treatment as an "oversolution" treatment, which has a higher temperature than the solution treatment temperature which means at least 10°C higher but not higher than 50°C, but preferably only three levels are used.
• One exemplary embodiment of the invention C: 0.072%, Cr: 8.1%, Co: 9.2%, W: 9.5%, Mo: 0.5%, Ta: 3.3%, Al: 5.4%, Ti: 0.5%, B: 0.015%, Hf: 1.2%, Zr: 0.01%.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Turbine Rotor Nozzle Sealing (AREA)

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Citations (3)

• 2022
  • 2022-12-19 EP EP22214482.6A patent/EP4389924A1/de not_active Withdrawn
• 2023
  • 2023-11-22 CN CN202380086869.XA patent/CN120380181A/zh active Pending
  • 2023-11-22 EP EP23809622.6A patent/EP4602189A1/de active Pending
  • 2023-11-22 WO PCT/EP2023/082688 patent/WO2024132348A1/en not_active Ceased

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