nickel-based alloy

Abstract

The present invention relates to a dispersion strengthened alumina-forming nickel-base alloy containing, in weight percent (wt%): C 0.08-0.28; Si 0-1.50; Mn 0-0.50; Cr 15.0-20.0; Al 4.0-5.0; Fe 15.0-25.0; N 0.030-0.075; O 0-0.1; B 0-0.02; Y 0.01-0.1; at least one of Ta, Zr, Hf, Ti, and Nb 1.0-2.7; balance Ni, and normally occurring impurities, the alloy comprising: (C+N) / (Ta+Zr+Hf+Nb+Ti) ≥ 1.4 (value in at%) [1]; Zr+Hf-N≧0.05 (values ​​in at%) [2] This alloy has excellent hot ductility.

Description

[Technical Field]

[0001] The present disclosure relates to alumina-forming nickel-base alloys and powders containing the alumina-forming nickel-base alloys. The disclosure also relates to objects made from the alloys or powders and uses thereof. [Background technology]

[0002] Nickel-based alloys alloyed with aluminum form a stable protective aluminum oxide on the surface, providing very good oxidation resistance and are therefore used in a variety of high temperature applications, for example in heat treatment furnaces.

[0003] Aluminum oxide-forming nickel-based alloy objects (e.g., wire and tubing) are known to be difficult to fabricate due to poor hot ductility, which is largely due to intermetallic phases that form during slow cooling / heating (e.g., during heat treatment or hot working) below approximately 900° C. These intermetallic phases make the alloy hard and brittle, making it difficult to fabricate.

[0004] The present disclosure aims to solve these problems.

[0005] Disclosure Overview The present disclosure thus relates to nickel-base alloys that meet certain requirements regarding carbon and carbides, and nitride-forming elements, and the inventors have surprisingly discovered that meeting these requirements ensures that objects made from the alloy, or powders made from the alloy, will have excellent hot ductility after hot isostatic pressing (HIP). This excellent hot ductility ensures that there will be substantially no crack formation during the hot working manufacturing process used to produce the object. Furthermore, the nickel-base alloys provide objects made from the alloy with excellent oxidation resistance and good creep strength at high temperatures.

[0006] Thus, the present disclosure provides a dispersion strengthened alumina-forming nickel-base alloy comprising, in weight percent (wt%): C 0.08~0.28; Si 0~1.5; Mn 0~0.50; Cr 15.0~20.0; Al 4.0~5.0; Fe 15.0~25.0; N 0.030~0.075 O<0.1 B < 0.02; Y 0.01~0.1 At least one of Ta, Zr, Hf, Ti and Nb 1.0~2.7; The balance is Ni and commonly occurring impurities Contains (C+N) / (Ta+Zr+Hf+Nb+Ti) ≥ 1.40 (value in at%) [1]; Zr+Hf-N≧0.05 (values ​​in at%) [2] This invention relates to a nickel-based alloy that meets the requirements of

[0007] The inventors have surprisingly found that when a nickel-based alloy falls within the elemental ranges specified above or below and further satisfies requirements [1] and [2], an object containing the alloy is guaranteed to have excellent hot ductility. This means that the object can be hot worked in further processes to obtain the desired product without crack formation. In addition, nickel-based alloys have an austenitic microstructure and have very good oxidation resistance, especially at high temperatures (e.g., temperatures above 900°C). Furthermore, the alloys provide good creep resistance.

[0008] According to some embodiments, the alloy can then be converted into a powder that can be used to manufacture objects. The powder can be used in a HIP process or an additive manufacturing process (e.g., 3D printing).

[0009] According to embodiments, an object as defined herein above or below is a HIPed object (e.g., a part or product), a HIPed object being an object obtained from a hot isostatic pressing process. According to embodiments, an object as defined herein above or below has been obtained using additive manufacturing.

[0010] The term "desired product" is intended to include, for example, wire, bar, hollow bar, hollow body, strip, tube, seamless tube, rod or plate, all of which forms can be produced without the problem of cracking during hot working processes. Examples of hot working processes are rolling, forging, and / or extrusion.

[0011] According to the present disclosure, the nickel-based alloy is a dispersion-strengthened alloy. This effect is achieved by adding one or more elements selected from the group consisting of Ta, Zr, Hf, Ti, and Nb. These elements form dispersion-strengthened particles with C and / or N (optionally, O is added). Dispersion hardening contributes to mechanical strength and provides excellent creep strength. Therefore, the alloy has excellent mechanical properties, especially at high temperatures.

[0012] This disclosure also relates to powders produced from this alloy, having the same requirements (i.e., [1] and [2]) and alloying element ranges. The powders can be produced by powder metallurgy. The powder metallurgy production process results in a rapidly solidified material, which does not have time for brittle phases to form and does not experience large compositional variations due to segregation. Thus, the rapidly solidified powder mixture results in a metal body having a substantially homogeneous composition and a substantially uniform distribution of very small dispersed particles.

[0013] Examples of suitable uses of the alloy include: as construction material for heat treatment furnaces, in rollers of roller hearth furnaces, as muffle tubes for annealing in protective atmospheres, as construction material for heating elements, as combustion chamber material for gas turbines, as gas-to-gas heat exchangers (e.g. in the glass manufacturing industry or in gas turbines), as wire-woven conveyor belts intended for heat treatment furnaces, in heating radiant tubes in heat treatment furnaces or as protective tubes for thermocouples. DETAILED DESCRIPTION OF THE INVENTION

[0014] The invention will be explained in more detail below with reference to various exemplary embodiments. However, the invention is not limited to the exemplary embodiments discussed, but may vary within the scope of the appended claims.

[0015] Furthermore, the dispersion strengthened nickel-base alloys described herein may exist in any possible form and / or state without departing from this disclosure unless expressly stated otherwise.

[0016] As mentioned above, nickel-based alloys alloyed with aluminum are generally considered difficult to use in the manufacture of objects and parts due to their poor hot ductility. The hot ductility of an alloy is a very important factor for ease of manufacture. The inventors have surprisingly discovered a nickel-based alloy containing the above or below alloying element ranges and satisfying the following requirements: (C+N) / (Ta+Zr+Hf+Nb+Ti) ≥ 1.4 (value in at%) [1]; Zr+Hf-N≧0.05 (values ​​in at%) [2] We have discovered that nickel-based alloys that satisfy these criteria have excellent hot ductility, even in the HIPed condition and during the hot working processes used in manufacturing processes. Therefore, the alloys can be fabricated into desired products without substantially forming cracks in the final product. Therefore, without being bound by any theory, it is believed that these requirements provide a balance between carbide and nitride-forming elements, thereby ensuring that harmful brittle phases are not formed. Therefore, through extensive research, the inventors have been able to identify which elements are necessary in nickel-based alloys and to what extent they need to be controlled to ensure good hot ductility without affecting weldability, oxidation resistance, and creep properties. According to several embodiments, (C + N) / (Ta + Zr + Hf + Nb + Ti) is 1.50 to 1.75. According to several embodiments, Zr + Hf - N is 0.18 to 0.38.

[0017] Hot isostatic pressing (HIP) is a process in which powder is subjected to high temperature and pressure in an inert gas atmosphere. This transforms the powder into a body / object and eliminates internal voids and microporosity through a combination of plastic deformation, flow, and diffusion bonding. Suitable process temperatures are 900-1250°C, suitable pressures are 80-200 MPa, and suitable hold times are 1-3 hours.

[0018] Where ranges are disclosed in this disclosure, the ranges include each of the endpoints unless expressly disclosed otherwise. Similarly, where open ranges (specifying only one upper or lower limit) are disclosed, the open range also includes one endpoint of the open range unless expressly disclosed otherwise.

[0019] The significance of the different alloying elements in the nickel-base alloys described herein is briefly discussed below. All percentages in chemical compositions are given in weight percent (wt%) unless expressly disclosed otherwise. As specified below, the upper and / or lower limits for individual elements for the compositions disclosed herein may be freely combined within the broadest range of the nickel-base alloy composition set forth in the claims, unless expressly disclosed otherwise.

[0020] carbon Free carbon occupies interstitial sites in the crystal structure, thereby locking dislocation mobility at temperatures up to approximately 400-500°C. Carbon also forms carbides with other elements in the alloy, such as Ta, Ti, Hf, Zr, and Nb. In microstructures containing finely dispersed carbides, these carbides act as obstacles to dislocation movement, even at high temperatures. Carbon is an essential element for improving creep strength. However, if the C content is too high, the ductility at low temperatures (e.g., below 300°C) decreases, making cold working of the alloy difficult. Therefore, the carbon content is 0.08-0.28 wt%. According to several embodiments, the carbon content is 0.15-0.28 wt%, for example, 0.20-0.28 wt%.

[0021] silicon Silicon may be present in a content of up to 1.5 wt%. Too high a level of Si may increase the risk of nickel silicide precipitation, which affects the brittleness of this type of alloy. According to some embodiments, the Si content is 1.0 wt% or less. According to some embodiments, the Si content is 0.30 wt% or less. According to some embodiments, the Si content is 0.001 wt% or more.

[0022] manganese Manganese is present as an impurity. A maximum of 0.50 wt% can be tolerated without negatively affecting properties. According to some embodiments, Mn is an impurity and its content is a maximum of 0.05 wt%. According to some embodiments, the Mn content is 0.001 wt% or more.

[0023] chromium To obtain oxides with sufficient oxidation resistance at high temperatures, the chromium content is preferably at least 15.0 wt%. However, a nickel-based alloy containing 4.0 wt% Al preferably does not contain more than about 20.0 wt% Cr, as the higher the chromium content, the greater the risk of brittle phase formation. According to some embodiments, the chromium content is 15.0-20.0 wt%, for example, 17.0-19.0 wt%.

[0024] aluminum Aluminum is an element that forms a protective, dense oxide scale. Therefore, the alloy contains at least 4.0 wt% Al, which ensures sufficient oxidation resistance at high temperatures and complete oxide surface coverage. Above 5.0 wt% Al, there is a risk of a significant decrease in hot ductility, so the maximum Al content is 5.0 wt%. According to some embodiments, the Al content is 4.0-4.5 wt%.

[0025] iron In accordance with the present disclosure, a relatively high content of Fe in nickel-based alloys that form aluminum oxide has been shown to have a positive effect. Adding Fe creates a metal structure that is energetically unfavorable for the formation of embrittled γ' phase, and risks making the alloy hard and brittle. Therefore, the nickel-based alloy contains at least 15.0 wt% Fe. However, a high iron content can lead to the formation of undesirable phases. Therefore, the alloy does not contain more than 25.0 wt% Fe. According to some embodiments, the iron content is 17.0-23.0 wt%, e.g., 18.0-21.0 wt%, e.g., 18.0-20.0 wt%, e.g., 19.0-20.0 wt%.

[0026] nickel The alloys according to the present disclosure are nickel-based. Nickel is an alloying element that stabilizes the austenitic structure, thereby counteracting the formation of brittle intermetallic compounds such as σ-phase. The austenitic structure is beneficial, for example, in connection with welding. The austenitic structure also contributes to good creep strength at high temperatures. Ni is the balance of the alloying elements.

[0027] nitrogen Like carbon, free nitrogen occupies interstitial sites in the crystal structure, thereby locking dislocation mobility at temperatures up to approximately 400-500°C. Nitrogen also forms nitrides and / or carbonitrides with other elements (e.g., Ta, Ti, Hf, Zr, and Nb). In microstructures where these particles are finely dispersed, they impede dislocation mobility, especially at high temperatures. Therefore, nitrogen is added to improve creep strength. However, when adding nitrogen to aluminum alloys, if not added carefully, aluminum nitride formation can become a problem, so the nitrogen content is limited to 0.030-0.075 wt%. According to several embodiments, the nitrogen content is 0.040-0.060 wt%.

[0028] oxygen Oxygen may be present in the alloy at up to 0.1 wt%. Oxygen can improve the creep strength of the alloy by forming small oxide dispersions with Zr, Hf, Ta, and Ti, which, when finely distributed in the alloy, improve creep strength. These oxide dispersions have higher melting temperatures than the corresponding carbides and nitrides, making oxygen a preferred additive for high-temperature applications. Oxygen can also form dispersions with Al, Group 3 elements of the periodic table, Sc, Y, La, and the fourteen lanthanides, contributing to the improvement of the alloy's creep strength in the same manner as the previously identified elements. According to some embodiments, the nickel-based alloy contains 20 to 1000 ppm O, e.g., 50 to 300 ppm O.

[0029] Tantalum, hafnium, zirconium, titanium, and niobium The elements Ta, Hf, and Zr form very small, stable particles with carbon and nitrogen. When these particles are finely dispersed within the structure, they help increase creep strength by locking dislocation movement (i.e., providing dispersion hardening). The addition of Ti can also achieve this effect. Niobium may also be suitably added to the alloy to form stable dispersions with C and / or N. Thus, the total content of Ta, Zr, Hf, Ti, and Nb is 1.0 to 2.7 wt%. According to several embodiments, the total content of Ta, Zr, Hf, Ti, and Nb is 1.4 to 2.3 wt%, for example, 1.6 to 2.0 wt%.

[0030] Although the total content is as described above, there are some limitations on the content of each element, and according to some embodiments, the content of Hf may be 0.3 to 0.7 wt%, according to other embodiments, the content of Zr may be 0.3 to 0.7 wt%, according to some embodiments, the content of Ta may be 0.3 to 0.7 wt%, and according to some embodiments, the content of Nb may be 0.3 to 0.7 wt%.

[0031] Yttrium (Y) Y influences the oxidation properties by doping the oxides formed: excessive alloying of this element often results in oxides that tend to exfoliate the surface, while adding too little of these elements tends to result in oxides that adhere poorly to the metal surface.

[0032] Boron (B) The addition of B has been shown to improve the hot ductility of nickel-based alloys. However, too high a B content reduces the melting point and narrows the temperature range in which the material can be worked, thereby reducing hot workability. Too high a B content can also impair desirable high-temperature properties. The powder may contain B in a content of up to 0.02 wt%. According to some embodiments, B is between 0.0001 and 0.02 wt%.

[0033] Additionally, either Ca or Mg can be added to improve the hot ductility of the material during the manufacturing process. Preferably, the calcium content is a maximum of 0.05 wt%, and more preferably 0.01 wt% or less. A maximum Mg content of 0.05 wt% may be preferred.

[0034] Nickel-base alloys according to the present disclosure may also contain normally occurring impurities as a result of the raw materials used or the manufacturing process selected. Examples of impurities are S and P. The alloys described herein may contain up to a total of 0.8 wt% normally occurring impurities in addition to the elements already identified and discussed above. For the purposes of this disclosure, normally occurring impurities are considered to be impurities that arise from the manufacturing process and / or the raw materials used. Amounts of normally occurring impurities of 0.6 wt% or less in total, or alternatively, 0.5 wt% or less in total, may be preferred, according to several embodiments.

[0035] Furthermore, the alloys, powders or bodies defined above or below may contain or consist of the elements defined above or below in any of the ranges mentioned herein.

[0036] Products (e.g. components) manufactured from the powders defined above or below are intended for use in particular at high temperatures. Examples of applications are construction materials for heat treatment furnaces, rollers in roller hearth furnaces, muffle tubes for annealing in protective atmospheres, construction materials for heating elements, combustion chamber materials in gas turbines, gas-to-gas heat exchangers (e.g. in the glass-making industry or in gas turbines), tubular reactors in high-temperature processes, wire-woven conveyor belts intended for heat treatment furnaces, radiant tubes for heating in heat treatment furnaces or protection tubes for thermocouples.

[0037] The invention is illustrated by the following non-limiting examples.

[0038] Example Various powders were produced by gas atomization, in which virgin raw materials were melted and poured into a ceramic nozzle, followed by exposure to nitrogen gas at a high flow rate. The gas flow broke the melt into small droplets, which rapidly solidified into spherical powder particles. The powder was then loaded into a welded sheet metal canister, degassed, sealed, and subjected to hot isostatic pressing (HIP). In the HIP process, the filled powder canister was held at high pressure (100 MPa) and high temperature (1150°C) in an argon atmosphere for three hours. This process densified the powder-filled canister into a fully dense body. The HIPed body was then hot rolled in several passes (total reduction of 70%). Specimens for Gleeble hot ductility tensile testing were extracted from the hot-rolled material in the rolling direction.

[0039] The composition of the powder produced is shown in Table 1 below.

[0040] Hot ductility tests were performed in this manner on the Gleeble system. Tensile specimens were heated to a set temperature with a specific heating profile / rate measured by thermocouples. The set temperature could be reached by heating to the desired temperature (ONH) or by cooling from a high temperature (ONC). After a specified hold time at the desired temperature, a tensile test was performed. The area reduction of the tensile specimen at the fracture point was then measured, which provides a measure of the hot ductility. The test results are shown in Table 2 below.

[0041] The hot ductility test in the Gleeble system constitutes a measure of a material's ability to withstand deformation at high temperatures without crack formation (i.e., hot ductility). As can be seen from Table 2, a heater that meets all the requirements specified above or below will exhibit good hot ductility in the form of high area reduction values ​​at high temperatures in the Gleeble test results. It should be noted that for a heater to be considered to have good hot ductility, the Gleeble test results must show an area reduction of ≥ 50% at 1150°C and ≥ 35% at 1050°C.

[0042] TIFF2025539887000001.tif245170

[0043] TIFF2025539887000002.tif210170

Claims

1. 1. A dispersion strengthened alumina-forming nickel-based alloy comprising, in weight percent (wt%): C 0.08-0.28; Si 0-1.50; Mn 0-0.50; Cr 15.0-20.0; Al 4.0-5.0; Fe 15.0-25.0; N 0.030-0.075; O 0-0.1; B 0-0.02; Y 0.01~0.1; at least one of Ta, Zr, Hf, Ti, and Nb 1.0 to 2.7; The balance is Ni and commonly occurring impurities. Contains (C + N) / (Ta + Zr + Hf + Nb + Ti) ≥ 1.4 (value in atomic %) [1]; Zr + Hf - N ≧ 0.05 (value in atomic %) [2] Dispersion strengthened alumina-forming nickel-based alloy that meets the requirements of

2. 2. The dispersion strengthened alumina-forming nickel-based alloy of claim 1, wherein the C content is 0.15-0.28 wt %, for example 0.20-0.28 wt % C.

3. 3. The dispersion strengthened alumina-forming nickel-based alloy according to claim 1, wherein the Si content is 0.30 wt. % or less.

4. 4. A dispersion strengthened alumina-forming nickel-based alloy according to claim 1, wherein Mn is an impurity and its content is up to 0.05 wt. %.

5. 5. The dispersion strengthened alumina-forming nickel-based alloy according to claim 1, wherein the Cr content is 17.0 to 19.0 wt %.

6. A dispersion strengthened alumina-forming nickel-based alloy according to any one of claims 1 to 5, wherein the Fe content is 18.0 to 21 wt%, for example 18.0 to 20.0 wt%.

7. A dispersion strengthened alumina-forming nickel-based alloy according to any one of claims 1 to 6, wherein the oxygen content is from 20 to 1000 ppm, for example from 50 to 300 ppm O.

8. 8. A dispersion strengthened alumina-forming nickel-based alloy according to any one of claims 1 to 7, wherein the total content of Ta, Zr, Hf, Ti and Nb is 1.4 to 2.3 wt%, for example 1.6 to 2.0 wt%.

9. A powder comprising the dispersion strengthened alumina-forming nickel-based alloy of any one of claims 1 to 8.

10. 10. An object made from the dispersion strengthened alumina-forming nickel-based alloy or powder according to any one of claims 1 to 9.

11. 11. The body of claim 10, which is a hot isostatically pressed body.

12. 12. The object according to claim 10 or 11, in the form of a tube, hollow body, bloom, bar, rod, strip, plate or wire.

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