Corrosion-resistant nickel-based alloy

Abstract

Disclosed is a nickel-base alloy having improved localized corrosion resistance, stress corrosion cracking (SCC) resistance, and impact strength. The improvements are due to an alloy composition that is less prone to the formation of deleterious phases and the addition of alloying elements that improve corrosion resistance, impact strength, and SCC resistance. The nickel-base alloy of the present invention has controlled amounts of Ni, Cr, Fe, Mo, Co, Cu, Mn, C, N, Si, Ti, Nb, Al, and B. The nickel-base alloy retains its corrosion resistance and desirable impact strength when subjected to post-cladding heat treatment or welding.

Description

[Technical Field]

[0001] <Cross-reference of related applications> This application claims the benefit of U.S. Provisional Patent Application No. 62 / 987,154, filed on 9 March 2020, which is incorporated herein by reference.

[0002] This invention relates to a nickel-based alloy having good corrosion resistance, mechanical properties, and weldability. [Background technology]

[0003] The information presented in this background section is not necessarily considered prior art.

[0004] Conventional Ni-based 625 alloy (UNS N06625) is one of the most widely used Ni-Cr materials in the oil, gas, and chemical processing industries due to its excellent corrosion resistance. However, 625 alloy is expensive. Conventional Ni-based 825 alloy (UNS N08825) is a Ni-Fe-Cr material widely used in these industries. While 825 alloy is less expensive than 625 alloy, its corrosion resistance is substantially lower, and stress corrosion cracking, pitting, and crevice corrosion can occur, especially in high-chloride water environments.

[0005] For example, there are many materials that have corrosion resistance properties between 825 alloy and 625 alloy, such as super austenitic alloys and super duplex alloys. While such alloys are suitable for many applications, there are also applications where they are not well-suited. Two such applications are hot-roll bonded pipes (HRBP) and containers made by bimetallic processing. In the manufacture of these products, corrosion-resistant alloys such as 625 alloy and 825 alloy are bonded or clad to carbon steel or other substrates. Depending on the bonding method used, heat treatment may be required after welding, cladding, and / or forming. Such post-clad heat treatment (PCHT) is often performed in a temperature range where intermetallic phases such as carbides, nitrides, and sigma can be formed. These phases are detrimental to the corrosion resistance and impact strength of many nickel-based alloys and all super austenitic and super duplex alloys.

[0006] Conventional 625 and 825 alloys have been traditionally chosen as materials for non-clad products and clad products such as HRBP and bimetallic processed containers because they maintain their properties substantially better after PCHT than super austenitic alloys and super duplex alloys. However, no industrial alloy is known that can adequately fill the gap between 625 and 825 alloys in terms of cost, chloride pitting corrosion properties, and SCC properties suitable for clad products requiring PCHT, such as HRBP and bimetallic processed containers.

[0007] Several alloys disclosed in U.S. Patents 4,545,826 and 10,174,397 attempt to bridge the corrosion resistance gap between 625 and 825 alloys by increasing the Mo, Cr, and / or N content of the 825 alloy to enhance pitting resistance. However, these alloys are susceptible to corrosion fracture, such as stress corrosion cracking (SCC), and may become brittle during PCHT. Other alloys, such as the alloy disclosed in PCT application WO2018 / 029305, address SCC resistance and brittleness issues by increasing Ni content by well over 50%, but such high Ni content negates much or all of the cost savings associated with 625 alloys. [Overview of the project]

[0008] The present invention includes a nickel-based alloy having desirable corrosion resistance properties, which include good local corrosion resistance, stress corrosion cracking resistance, and intergranular corrosion resistance. The nickel-based alloy also has good mechanical properties and weldability. This is due to an alloy composition that is less prone to the formation of harmful phases and the addition of alloying elements that improve corrosion resistance, mechanical properties, and weldability. This nickel-based alloy may be subjected to post-cladding heat treatment or welding processes while maintaining good corrosion resistance and impact strength. The nickel-based alloy of the present invention is suitable as a substitute material for 825 alloy and 625 alloy for non-cladded products and cladded products such as HRBP and bimetallic containers. Furthermore, the nickel-based alloy of the present invention can also be used as a substitute material for super austenitic alloys and super duplex alloys in other applications, particularly in applications where improved phase stability, chloride pitting corrosion resistance, and SCC resistance are required. The Ni-based alloy of the present invention is less expensive than 625 alloy, possesses SCC resistance, pitting corrosion resistance, crevice corrosion resistance, and intergranular corrosion resistance equivalent to or better than 825 alloy, and has greater resistance to property degradation after high-temperature processing such as heat treatment (PCHT) and welding compared to super austenitic and super duplex alloys.

[0009] One aspect of the present invention is to provide a nickel-based alloy containing 38-60 wt% Ni, 19-25 wt% Cr, 15-35 wt% Fe, 3-7 wt% Mo, and 0.1-10 wt% Co. This nickel-based alloy has at least one of the following properties: a Charpy impact energy of 100 ft-lbs or more, measured using a 5 mm specimen at -50°C according to ASTM E23-18; a critical pitting temperature higher than 95°F, measured according to ASTM G48 Method C; an intergranular corrosion rate of less than 0.25 mm / year, measured according to ASTM G28 Method A; and stress corrosion cracking resistance longer than 1000 hours, measured according to ASTM G36.

[0010] Another aspect of the present invention provides a method for producing a nickel-based alloy containing 38-60 wt% Ni, 19-25 wt% Cr, 15-35 wt% Fe, 0.1-10 wt% Co, and 3-7 wt% Mo. The method includes homogenizing an ingot of a nickel-based alloy, processing the homogenized ingot to form a slab or billet, further hot-rolling to form a plate-like, rod-like, or tubular product, annealing the product, and cooling the annealed product. This nickel-based alloy has at least one of the following properties: a Charpy impact energy of 100 foot-pounds or more, measured using a 5 mm specimen at -50°C according to ASTM E23-18; a critical pitting temperature higher than 95°F, measured according to ASTM G48 Method C; an intergranular corrosion rate of less than 0.25 mm / year, measured according to ASTM G28 Method A; and stress corrosion cracking resistance longer than 1000 hours, measured according to ASTM G36.

[0011] These and other aspects of the present invention will become clearer from the following description. [Brief explanation of the drawing]

[0012] The various features and characteristics of the present invention described in this specification can be more fully understood by referring to the accompanying drawings.

[0013] [Figure 1] Figure 1 is a graph comparing the sigma solvus temperatures calculated for various nickel-based alloys of the present invention with a comparative alloy.

[0014] [Figure 2] Figure 2 is an optical micrograph of the nickel-based alloy of the present invention in a solution annealed condition. [Figure 3] Figure 3 is an optical micrograph of the nickel-based alloy of the present invention in a PCHT condition. [Figure 4] Figure 4 is an optical micrograph of the comparative alloy in a solution annealed condition. [Figure 5] Figure 5 is an optical micrograph of the comparative alloy in a PCHT condition.

[0015] [Figure 6] Figure 6 is a SEM micrograph of the nickel-based alloy of the present invention in a solution annealed condition, and the upper image is taken at a lower magnification than the lower image. [Figure 7] Figure 7 is a SEM micrograph of the nickel-based alloy of the present invention in a PCHT condition, and the upper image is taken at a lower magnification than the lower image.

[0016] [Figure 8] Figure 8 is a SEM micrograph of the comparative alloy in a solution annealed condition, and the upper image is taken at a lower magnification than the lower image. [Figure 9] Figure 9 is a SEM micrograph of the comparative alloy in a PCHT condition, and the upper image is taken at a lower magnification than the lower image.

[0017] [Figure 10] Figure 10 is a SEM micrograph of another comparative alloy in a solution annealed condition, and the upper image is taken at a lower magnification than the lower image. [Figure 11]Figure 11 is a SEM photograph of the PCHT state of another comparative alloy. The upper image was taken at a lower magnification than the lower image.

[0018] [Figure 12] Figure 12 is a SEM photograph of the solution annealing state of another comparative alloy. The upper image was taken at a lower magnification than the lower image. [Figure 13] Figure 13 is a SEM photograph of the PCHT state of another comparative alloy. The upper image was taken at a lower magnification than the lower image. <�

[0019] [Figure 14] Figure 14 is a SEM photograph of the solution annealing state of another comparative alloy. The upper image was taken at a lower magnification than the lower image. [Figure 15] Figure 15 is a SEM photograph of the PCHT state of another comparative alloy. The upper image was taken at a lower magnification than the lower image.

[0020] [Figure 16] Figure 16 is a graph of the Charpy impact energy in the longitudinal direction, comparing various nickel-based alloys of the present invention with comparative alloys both with and without PCHT. The decrease in impact strength after PCHT indicates that the alloys of the present invention have less decrease than the comparative alloys.

[0021] [Figure 17] Figure 17 is a graph of the Charpy impact energy in the width direction, comparing various nickel-based alloys of the present invention with comparative alloys both with and without PCHT. The decrease in impact strength after PCHT indicates that the alloys of the present invention have less decrease than the comparative alloys.

[0022] [Figure 18] Figure 18 is a graph comparing the yield strengths of the nickel-based alloys of the present invention and three comparative alloys in the solution annealing state and the PCHT state.

[0023] [Figure 19] Figure 19 is a graph comparing the tensile strength of the nickel-based alloy of the present invention and three comparative alloys in the solution annealed state and the PCHT state.

[0024] [Figure 20] Figure 20 is a graph comparing the percentage elongation of the nickel-based alloy of the present invention and three comparative alloys in the solution annealing state and the PCHT state.

[0025] [Figure 21] Figure 21 is a graph comparing the Rockwell B hardness of the nickel-based alloy of the present invention and three comparative alloys in the solution annealed state and the PCHT state.

[0026] [Figure 22] Figure 22 is a graph comparing the Charpy impact energies of the nickel-based alloy of the present invention and three comparative alloys in the solution annealed state and the PCHT state.

[0027] [Figure 23] Figure 23 is a graph comparing the critical pitting temperatures of the nickel-based alloy of the present invention and three comparative alloys in the solution annealing state and the PCHT state.

[0028] [Figure 24] Figure 24 is a graph comparing the intergranular corrosion rates of the nickel-based alloy of the present invention and three comparative alloys in the solution annealing state and the PCHT state.

[0029] [Figure 25] Figure 25 is a graph comparing the stress corrosion cracking resistance of the nickel-based alloy of the present invention and three comparative alloys in solution annealing and PCHT conditions.

[0030] [Figure 26] Figure 26 is an optical microscope image of the welding zone of the nickel-based alloy of the present invention.

[0031] [Figure 27] Figure 27 is a graph comparing the intergranular corrosion rates of the nickel-based alloy of the present invention and three comparative alloys in the solution annealed state and the PCHT state. The intergranular corrosion rate of the welded portion of the nickel-based alloy of the present invention is also shown. [Modes for carrying out the invention]

[0032] <Detailed explanation> The nickel-based alloy of the present invention may have controlled amounts of Ni, Cr, Fe, Mo, and Co, and controlled amounts of Cu, Mn, C, N, Si, Ti, Nb, B, and Al. Such alloying additives can be provided in the contents shown in Table 1 below. Other elements may be included as adjustments for the technical advantage of improving workability, such as V, W, Mg, and rare earth metals. Elements such as P, S, and O may be present in trace amounts as unavoidable impurities, but such elements are not intentionally added to the nickel-based alloy of the present invention. As used herein, “incidental impurities” means elements that are not intentionally added as alloying additives to the nickel-based alloy composition, but are present as unavoidable impurities or in trace amounts. The term “substantially absent” in reference to the alloy composition of the present invention means that an element is present only as an incidental impurity. [Table 1]

[0033] As shown in Table 1 above, the nickel-based alloys of the present invention may contain, in weight percent, Ni 38.0-60.0, Cr 19.0-25.0, Fe 15.0-35.0, Mo 3.0-7.0, and Co 0.1-5.0. The nickel-based alloys may further contain, in weight percent, additional elements such as Cu 0.1-4.0, Mn 0.1-3.0, C ≤ 0.030, N ≤ 0.15, Si ≤ 1.0, Ti ≤ 0.10, Nb ≤ 0.20, Al ≤ 0.30, B ≤ 0.0050, V ≤ 0.3, W ≤ 0.3, and Mg ≤ 0.01, or any combination of these additional elements. The compositions of the examples shown in Table 1 exemplify feasible nickel-based alloys of the present invention.

[0034] The amounts of Cr, Mo, and N can be selected to obtain sufficient pitting corrosion resistance. The pitting resistance equivalent number (PREN) is calculated based on the formula PREN = %Cr + 3.3(%Mo) + 16(%N). A higher PREN indicates better resistance to chloride-induced pitting and crevice corrosion. The PREN of nickel-based alloys is at least 40, and in some examples, it can be between 41 and 45.

[0035] Nickel-based alloys may contain 38.0 to 60.0% Ni by weight, or any range encompassed within the aforementioned range, for example, 38.0 to 55.0; 39.0 to 50.0; 39.0 to 49.0; 39.5 to 50.0; 39.5 to 49.5; 40.0 to 50.0; 40.0 to 49.0; 40.0 to 48.0; 40.5 to 49.5; 41.0 to 48.0; 41.5 to 48.0; 41.5 to 47.5; 42.0 to 48.0; 41.5 to 46.5; 41.5 to 46.0; 42.0 to 46.0; 42.5 to 48.0; 41.5 to 45.5; or 41.5 to 44.0. Ni content of 38.0–60.0 wt%, and in some embodiments, 40.0–48.0 wt%, provides stress corrosion cracking resistance, phase stability, good mechanical properties, and fabricability. However, to reduce the Ni content while maintaining material performance, the Ni content can be maintained in the range of 40.0–48.0 wt%, or any range encompassed within that range. In certain alloys, the Ni content is less than 48.0 wt%, or less than 47.0 wt%, or less than 46.0 wt%, or less than 45.0 wt%, or less than 44.0 wt%. Also, in certain alloys, the nickel content is greater than 38.0 wt%, or greater than 38.5 wt%, or greater than 39.0 wt%, or greater than 39.5 wt%, or greater than 40.0 wt%, or greater than 40.5 wt%, or greater than 41.5 wt%, or greater than 42.0 wt%, or greater than 42.5 wt%.

[0036] Nickel-based alloys may contain 19.0–25.0% Cr by weight, or any range encompassed within the aforementioned range, for example, 20.0–25.0; 21.0–25.0; 22.0–25.0; 20.0–24.0; 21.0–24.0; 22.0–24.0; 20.0–23.0; 21.0–23.0; 22.0–23.0; 21.5–24.5; 21.5–23.5; or 21.5–23.0. 19.0–25.0% by weight of Cr, or in some embodiments, 21.0–25.0% by weight of Cr, provides resistance to oxidative corrosive media, chloride-induced pitting corrosion, and crevice corrosion. In certain alloys, the Cr content is greater than 19.0 wt%, or greater than 19.5 wt%, or greater than 20.0 wt%, or greater than 20.5 wt%, or greater than 21.0 wt%, or greater than 21.5 wt%, or greater than 22.0 wt%. In a specific example, the Cr content may be about 22 wt%. Excessive addition of Cr, for example, exceeding 25.0 wt%, can promote the formation of harmful phases.

[0037] Nickel-based alloys may contain 3.0–7.0% by weight of Mo, or any range encompassed within the aforementioned range, for example, 3.0–6.5; 3.5–6.5; 4.0–6.5; 4.5–6.5; 5.0–6.0; 4.5–6.0; or 5.0–6.0. ​​3.0–7.0% by weight of Mo, or in some embodiments, 4.0–6.5% by weight of Mo, provides resistance to non-oxidative (reducing) corrosive media, chloride-induced pitting and crevice corrosion, and stress corrosion cracking. In certain alloys, the Mo content is less than 7.0% by weight, or less than 6.5% by weight, or less than 6.0% by weight, or less than 5.8% by weight. In certain embodiments, the Mo content may be about 5.5% by weight. Too much Mo, for example exceeding 7.0% by weight, may promote the formation of harmful phases. When increasing the amount of Mo to improve corrosion resistance, it is possible to balance this with other compositional changes in order to suppress the formation of harmful phases and not degrade mechanical properties.

[0038] Nickel-based alloys may contain 0.1 to 5.0% by weight of Co, or any range encompassed within the above range, e.g., 0.1 to 4.0; 0.1 to 3.0; 0.10 to 2.60; 0.2 to 4.5; 0.2 to 4.0; 0.2 to 3.5; 0.2 to 3.0; 0.20 to 2.60; 0.25 to 3.50; 0.25 to 3.00; or 0.25 to 2.60. 0.1 to 5.0% by weight of Co, or in some embodiments, 0.25 to 2.60% by weight of Co, in combination with the above Ni content, increases resistance to stress corrosion cracking (SCC), provides desirable impact strength, and offers solid solution strengthening. The addition of Co can have beneficial effects on impact toughness and SCC resistance, and these effects can be enhanced by other alloying additions described herein. In certain alloys, the Co content may be greater than 0.25 wt%, or greater than 0.5 wt%, or greater than 1.0 wt%, or greater than 1.5 wt%. However, since Co is a relatively expensive element, in some embodiments, the Co content may be maintained in the range of 0.1 to 3.0 wt%, or any range within that range, for example, 0.25 to 2.60 wt%, in order to control costs while improving material performance.

[0039] Nickel-based alloys may contain 0.1 to 4.0% by weight of Cu, or any range encompassed within that range, such as 0.2 to 4.0; 0.2 to 3.0; 0.2 to 2.5; 0.2 to 2.0; or 0.25 to 2.00. Cu of 0.1 to 4.0% by weight, or in some embodiments, 0.2 to 2.0% by weight, provides corrosion resistance to reducing environments such as sulfuric acid and enhances resistance to crack formation in the presence of H2S. However, too much Cu, for example exceeding 4.0% by weight, negatively affects hot workability and thermal stability.

[0040] Nickel-based alloys may contain 0.1 to 3.0% by weight of Mn, or any range encompassed within that range, for example, 0.2 to 3.0; 0.2 to 2.5; 0.2 to 2.0; 0.25 to 2.00; or 0.25 to 1.50. 0.1 to 3.0% by weight of Mn, or in some embodiments, 0.25 to 2.00% by weight of Mn, results in improved solubility and strength of N. If the amount of Mn added is too high, for example, exceeding 3.0% by weight, impact strength and resistance to localized corrosion may decrease.

[0041] Nickel-based alloys may contain up to 1.0% by weight of Si, or any range encompassed within the aforementioned range, e.g., 0.9% or less; 0.75% or less; 0.6% or less; 0.5% or less; 0.4% or less; 0.001 to 1.0%; 0.001 to 0.9%; 0.001 to 0.75%; 0.001 to 0.6%; 0.001 to 0.5%; 0.001 to 0.4%; 0.01 to 1.0%; 0.01 to 0.50%; 0.01 to 0.40%; 0.05 to 1.0%; 0.05 to 0.50%; 0.05 to 0.40%; 0.10 to 0.50%; or 0.10 to 0.40%. Si has the effect of increasing the kinetics of harmful phase formation and therefore should be limited to 1% by weight or less, and in some embodiments, should be limited to 0.5% by weight or less or 0.4% by weight or less. Raw materials typically contain small amounts of silicon, and while it is possible to reduce the silicon content to less than approximately 0.05%, this would unnecessarily increase the cost of the alloy.

[0042] Nickel-based alloys may contain up to 0.15% by weight of N, or any range encompassed within the aforementioned range, e.g., 0.1% or less; 0.075% or less; 0.001–0.15%; 0.001–0.10%; 0.001–0.075%; 0.005–0.12%; 0.005–0.10%; 0.005–0.075%; 0.01–0.10%; 0.01–0.075%; or 0.015–0.075%. N up to 0.15% by weight, or in some embodiments, 0.01–0.1% by weight, provides strength and resistance to chloride-induced pitting and crevice corrosion. Too much N, for example, exceeding 0.15% by weight, can form chromium nitrides, which can adversely affect corrosion resistance and mechanical properties.

[0043] Nickel-based alloys may contain up to 0.1% by weight of Ti, or any range encompassed within the aforementioned range, e.g., 0.01-0.10; 0.01-0.08; 0.01-0.07; 0.01-0.06; 0.01-0.05; or 0.01-0.04. Ti up to 0.1% by weight, or in some embodiments, 0.01-0.07% by weight, preferentially reacts with C impurities to form titanium carbides, thereby reducing or eliminating the reaction between Cr and C. When Cr and C react, Cr-deficient zones are created around the chromium carbide particles, giving rise to corrosion initiation sites.

[0044] Nickel-based alloys may contain up to 0.2% Nb by weight, or any range encompassed within the aforementioned range, e.g., 0.01-0.20; 0.02-0.15; 0.02-0.10; 0.025-0.10; 0.025-0.095; 0.025-0.090; or 0.02-0.09. Nb up to 0.2% by weight, or in some embodiments, 0.02-0.1% by weight, preferentially reacts with C impurities to form niobium carbides, thereby reducing or eliminating the reaction between Cr and C. When Cr and C react, Cr-deficient zones are created around the chromium carbide particles, giving rise to corrosion initiation sites.

[0045] Nickel-based alloys may contain up to 0.005% by weight of B, or any range encompassing the aforementioned range, for example, 0.0001-0.0050; 0.0002-0.0050; 0.0004-0.0035; 0.0005-0.0050; 0.0009-0.0030; 0.0010-0.0030; or 0.0010-0.0020. B up to 0.005% by weight, or in some embodiments 0.001-0.003% by weight, strengthens grain boundaries and improves hot workability. B above about 0.005% may cause the formation of harmful boride precipitates.

[0046] Nickel-based alloys may contain up to 0.030% by weight of carbon, or any range encompassed within the aforementioned range, for example, 0.015% or less; 0.010% or less; 0.007% or less; 0.001 to 0.030%; 0.001 to 0.015%; 0.001 to 0.007%; 0.002 to 0.007%; or 0.003 to 0.007%. Carbon content of 0.030% by weight or less, or in some embodiments, 0.015% by weight or less, improves strength but can also combine with chromium to form harmful chromium carbide particles at grain boundaries, depleting chromium in the surrounding region. This is called boundary sensitization. By keeping carbon low, the occurrence of sensitization can be minimized. For this reason, it is preferable to maintain carbon below 0.03% by weight, and more preferably below 0.01% by weight.

[0047] In some embodiments of the present invention, the nickel-based alloy is substantially Mg-free. The term "substantially free" means that Mg is not intentionally added to the nickel-based alloy as an alloying additive, but is present only as a trace or incidental impurity. Such Mg-free alloys may contain the above-mentioned amounts of Ti to provide resistance to edge cracking during manufacturing. In other embodiments, a small amount of Mg, for example, up to 0.01% by weight, may be added to the nickel-based alloy to improve hot workability. Mg can be added in weight percentages up to 0.01, or within that range, for example, 0.005 or less, 0.001 to 0.01, or 0.001 to 0.005.

[0048] Nickel-based alloys may contain Al up to 0.30 by weight percentage, or any range included within the said range, for example, 0.25 or less; 0.20 or less; 0.15 or less; 0.10 or less, 0.01 to 0.30; 0.01 to 0.25; 0.01 to 0.20; 0.01 to 0.15; 0.01 to 0.10; 0.02 to 0.30; 0.03 to 0.20; 0.04 to 0.25; 0.04 to 0.15; 0.05 to 0.2; 0.05 to 0.15; 0.06 to 0.25; or 0.06 to 0.15. Nickel-based alloys may contain V up to 0.3 by weight percentage, or any range included within the said range, for example, 0.2 or less; 0.1 or less; or 0.05 or less. Nickel-based alloys may contain W up to 0.3 by weight percentage, or any range encompassed within the aforementioned range, for example, 0.25 or less; 0.20 or less; 0.15 or less; 0.1 or less; 0.001 to 0.3; 0.001 to 0.25; 0.001 to 0.20; 0.001 to 0.15; or 0.001 to 0.1.

[0049] The remainder of the nickel-based alloy composition may include iron and incidental impurities. In some embodiments, the remainder of the iron may be 15.0–35.0% by weight, or any range encompassed within that range, for example, 15.0–30.0; 16.0–29.0; 18.0–29.0; or 18.5–29.0.

[0050] The nickel-based alloy of the present invention can be melted and cast by metallurgical operations of an ingot. Examples of metallurgical operations include one or more of the following: argon oxygen decarburization (AOD), vacuum oxygen decarburization (VOD), vacuum induction melting (VIM), electroslag refining (ESR), and vacuum arc remelting (VAR). Cast ingots, slabs, or billets of the nickel-based alloy of the present invention can be subjected to a homogenization treatment for, for example, 12 to 96 hours, or for example, 2,000 to 2,350°F, or 2,100 to 2,200°F within the aforementioned temperature range, for 24 to 72 hours within the aforementioned time range. The homogenized product can then be processed at high temperatures, such as forging, at a temperature of 1,600 to 2,300°F, or any temperature range within the aforementioned temperature range, for example, 1,700 to 2,000°F. In the processing steps, the alloy can be formed into slabs or billets. This can be done by hot working, for example, by reheating at a temperature of 2,000 to 2,300°F, or any temperature range within that range, for example, 2,050 to 2,150°F, to form mill products with a desired thickness, such as plates, sheets, strips, foils, bars, tubular bodies, forged shapes, or coils. The thickness may be, for example, 0.001 to 4.0 inches, or any range within that range.

[0051] After hot working, the nickel-based alloy of the present invention can be annealed at a selected temperature, for example, 1,750 to 2,300°F, or any range within that range, for example, 1,800 to 2,150°F.

[0052] The annealed plate can be rapidly cooled from the annealing temperature to a temperature below 950°F, for example, at a rate of at least 300°F / min.

[0053] In some cases, the annealed material is then subjected to an additional heat treatment equivalent to the post-cladding heat treatment (PCHT) conventionally used for hot-rolled jointed tubes (HRBP) or bimetallic process vessels. PCHT can be carried out at temperatures of, for example, 1,100 to 1,800°F. In some cases, PCHT can be carried out in multiple stages at different temperatures. For example, it can be carried out at 1,750°F for 1 hour, followed by 1,100°F for 45 minutes.

[0054] The nickel-based alloy of the present invention can exhibit improved toughness after PCHT compared to certain conventional nickel-based alloys. The toughness of the nickel-based alloy of the present invention can be measured according to the "Standard Test Methods for Notched Bar Impact Testing of Metallic Materials" specified in ASTM E23-18, which is incorporated herein by reference. After the PCHT treatment described above, the nickel-based alloy of the present invention retains at least 85% of the initial toughness of the solution-annealed state, as measured as Charpy impact energy at -50°C according to ASTM E23-18. In other words, when measured at -50°C according to ASTM E23-18, the Charpy impact energy of the nickel-based alloy of the present invention in the PCHT state is not more than 15% less than the Charpy impact energy of the solution-annealed state in either the longitudinal or transverse direction with respect to the hot-rolling direction or other hot-working direction.

[0055] In some embodiments, after the PCHT treatment described above, the nickel-based alloy of the present invention maintains at least 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, or 95% of the initial toughness in the solution annealed state, with the Charpy impact energy measured at -50°C in accordance with ASTM E23-18. In other words, in some embodiments, the Charpy impact energy measured at -50°C in either the longitudinal or widthwise direction with respect to the hot rolling direction or other hot working direction, the nickel-based alloy of the present invention maintains the Charpy impact energy in the PCHT state at least 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, or 5% less than the Charpy impact energy in the solution annealed state.

[0056] In some embodiments, the Charpy impact energy of the nickel-based alloys of the present invention described above in the PCHT state, when measured at -50°C, is greater than that of the alloys in the solution-annealed state described above, in both the longitudinal and widthwise directions with respect to the hot-rolling or other hot-working direction. In contrast, some conventional nickel-based alloys have shown that the Charpy impact energy measured during PCHT decreases by at least 19%, and in some cases at least 50%, when measured in the longitudinal direction. In other words, such conventional Ni-based alloys, in the solution-annealed state after PCHT, are less than 81% of their initial toughness, and in some cases less than 50%.

[0057] The nickel-based alloy of the present invention, after the above-mentioned PCHT, has a Charpy impact energy of at least 100 ft-pounds in either the longitudinal or widthwise direction when measured at -50°C for a 5 mm size (thickness of a sample piece) according to ASTM E23-18, and in some embodiments, at least 110 ft-pounds, 111 ft-pounds, 113 ft-pounds, 115 ft-pounds, 117 ft-pounds, 119 ft-pounds, 120 ft-pounds, 122 ft-pounds, 123 ft-pounds, 125 ft-pounds, 126 ft-pounds, or 127 ft-pounds.

[0058] Nickel-based alloys treated with PCHT maintain desirable properties, including improved corrosion resistance, while maintaining or improving mechanical properties such as impact strength and fracture toughness. Mechanical testing includes Charpy impact testing and tensile testing to measure yield strength (YS), ultimate tensile strength (UTS), elongation (%E), and area loss rate (%RA). Corrosion testing includes chloride stress corrosion cracking (SCC), critical pitting temperature (CPT), and intergranular attack (IGA).

[0059] The following examples are for illustrating the features of the present invention and do not limit the scope of the invention. [Examples]

[0060] <Example 1> Nine heats of the nickel-based alloy of the present invention and four heats of comparative alloys were prepared, and their microstructures and Charpy impact energy properties were evaluated. Furthermore, for each heat, the pitting resistance index (PREN) (Cr + 3.3Mo + 16N), sigma solvus temperature, and average electron vacancy number (N) were evaluated. vThe average d-electron energy (metal-d) was calculated. Table 2 below shows the compositions of the nickel-based alloys of the nine inventive examples (heats 1-9) and the four comparative alloys (heats C1-C4). Ingots of the inventive and comparative alloy examples were prepared using laboratory-scale vacuum induction melting and electroslag refining. The ingots were homogenized and forged to diameters of 8 inches to 6 inches at temperatures of 2,000°F to 1,700°F. Each of the 6-inch diameter forges was multi-cut to approximately 50 pounds and forged into pancakes. These pancakes were cut into slabs, reheated and hot-rolled to produce plates approximately 0.27 inches thick. Each hot-rolled plate was cut into five test panels from each heat. [Table 2]

[0061] After rolling, the materials underwent solution annealing (SA) at a temperature of approximately 2,100°F (1,150°C). Additionally, some materials underwent simulated post-cladding heat treatment (PCHT), with the first stage at 1750°F (954°C) followed by the second stage at 1100°F (593°C). Tests were conducted on samples in both SA and PCHT states. Samples from each heat were used for microstructural analysis and Charpy impact energy testing in both the SA and PCHT states.

[0062] Table 2 shows the PREN values ​​and sigma-soluburst temperatures for each heat. The sigma-soluburst temperature was determined using the thermodynamic calculation software Thermo-Calc to find the highest temperature at which the sigma phase becomes thermodynamically stable for each composition. The composition of the alloy of the present invention may be optimized to minimize the formation of harmful phases during PCHT. Thermodynamic calculation software Thermo-Calc and average electron vacancy number (N v ) and average d-electron energy (M d Alternatively, the standard formula for metal-d) can be used to calculate phase stability based on alloy composition. v and M dThe applicable formula is described in Cieslak et al., "The Use of New PHACOMP in Understanding Solidification Microstructure of Nickel Base Alloy Weld Metal," Metallurgical Transactions A, Vol.17A (2107-16), December 1986, and this document is incorporated herein by reference. The sigma-solvus calculation results are shown in Figure 1 in comparison with the comparative alloy. Generally, a lower sigma-solvus temperature and N v There is a correlation between a smaller value of metal-d and better phase stability, indicating less formation of harmful intermetallic compounds. The low sigma-solvus temperature indicates that the alloy of the present invention is less likely to form harmful phases compared to certain conventional alloys. This improved phase stability allows solution annealing to be performed at lower temperatures, making the manufacturing and processing of the alloy easier and less expensive.

[0063] In the examples, the heat treatment involved varying the content of Ni, Fe, Mo, Mn, N, Co, Cu, and Nb, and measuring the effect of changing the concentrations of these elements on the corrosion properties and mechanical properties of the new alloys.

[0064] As shown in Table 2 above, the compositions of Heat No. 1 to 9 contain Ni in the range of approximately 40 to 48 weight percent, and as alloying additives, contain Cr in the range of approximately 21 to 23 weight percent, Mo in the range of approximately 4.0 to 6.0 weight percent, Co in the range of approximately 0.25 to 2.6 weight percent, Cu in the range of approximately 0.25 to 2 weight percent, Mn in the range of approximately 0.25 to 2 weight percent, N in the range of approximately 0.01 to 0.07 weight percent, Si up to approximately 1.0 weight percent, Ti in the range of approximately 0.01 to 0.05 weight percent, Nb in the range of approximately 0.02 to 0.1 weight percent, A1 in the range of 0.06 to 0.25 weight percent, C up to 0.015 weight percent, B in the range of 0.001 to 0.003 weight percent, with the remainder being Fe and incidental impurities.

[0065] Figures 2 and 3 are micrographs of the nickel-based alloy of the present invention (Heat 2) in the solution annealed and PCHT states, respectively. Figures 4 and 5 are micrographs of a conventional alloy for comparison (Heat C3) in the solution annealed and PCHT states, respectively. All samples were electroetched in oxalic acid using the same etching procedure. The microstructures of both alloys appeared similar in the solution annealed state, but simulated post-cladding heat treatment (PCHT), as indicated by the dark grain boundary regions in Figure 5, generated far more harmful phases, which precipitated at the grain boundaries of conventional alloy C3, causing degradation of its mechanical and corrosion properties, as shown in the data. This indicates that the alloy of the present invention is more suitable for applications requiring PCHT.

[0066] Figures 6 and 7 are SEM images of the nickel-based alloy Heat #6 of the present invention in the solution annealed state (Figure 6) and the PCHT state (Figure 7). The upper image was taken at a lower magnification than the lower image. The microstructure shown in Figures 6 and 7 substantially does not contain harmful grain boundary phases such as sigma in either the solution annealed state or the PCHT state, and therefore the corrosion susceptibility is significantly reduced.

[0067] Figures 8 and 9 are SEM images of the comparative alloy Cl in the solution annealed state (Figure 8) and the PCHT state (Figure 9). The upper image was taken at a lower magnification than the lower image. The bright areas in Figure 9 correspond to harmful phases such as sigma present at the grain boundaries. The presence of such grain boundary phases in the PCHT state of the comparative alloy Cl significantly increases the alloy's susceptibility to intergranular corrosion.

[0068] Figures 10 and 11 are SEM images of comparative alloy C2 in the solution annealed state (Figure 10) and the PCHT state (Figure 11). The upper image was taken at a lower magnification than the lower image.

[0069] Figures 12 and 13 are SEM images of comparative alloy C3 in the solution annealed state (Figure 12) and the PCHT state (Figure 13). The upper image was taken at a lower magnification than the lower image. The bright areas in Figure 13 correspond to harmful phases such as sigma present at the grain boundaries. The presence of such grain boundary phases in the PCHT state of comparative alloy C3 significantly increases the alloy's susceptibility to intergranular corrosion.

[0070] Figures 14 and 15 are SEM images of comparative alloy C4 in the solution annealed state (Figure 14) and the PCHT state (Figure 15). The upper image was taken at a lower magnification than the lower image. The bright areas in Figure 15 correspond to harmful phases such as sigma present at the grain boundaries. The presence of such grain boundary phases in the PCHT state of comparative alloy C4 significantly increases the alloy's susceptibility to intergranular corrosion.

[0071] Figures 16 and 17 are graphs showing the measurement results of a 5 mm thick V-notch impact test conducted at -50°C in accordance with ASTM E23-18 for the nickel-based alloy of the present invention and a conventional alloy. Figure 16 is a graph of the Charpy impact energy in the longitudinal direction, and Figure 17 is a graph of the Charpy impact energy in the width direction. Both figures show the state with and without PCHT. The test results show that the alloy of the present invention, which has undergone PCHT, has higher impact strength than the conventional alloy. As shown in these figures, the impact energy of most alloys decreases after PCHT. However, the decrease in impact energy of the alloy of the present invention (4.8% to 13.5% in the longitudinal direction and 2.4% to 11.3% in the width direction with respect to the hot rolling direction) is substantially less than that of the comparative alloy (18.8% to 51.2% in the longitudinal direction and 14.1% to 46.8% in the width direction with respect to the hot rolling direction). In other words, the alloy of the present invention retained 86.5% to 95.2% of its initial toughness in the longitudinal direction, while the comparative alloy was only able to retain 48.8% to 81.2%. Furthermore, the alloy of the present invention retained 88.7% to 97.6% of its initial toughness in the width direction, while the comparative alloy was only able to retain 53.2% to 85.9%. In fact, in the two alloys of the present invention with high Co content (Heat 4 and Heat 7), the impact energy in the longitudinal direction was unexpectedly higher than in the solution annealed state.

[0072] <Example 2> The alloy of Heat 6 described above was compared with comparative alloys C5, C6, and C7. Heat C5 has a composition similar to Heat C3 described above, containing nominal 6% by weight of Mo; Heat C6 has a composition similar to Heat C2 described above, corresponding to conventional alloy 825; and Heat C7 has a composition similar to Heat Cl described above, corresponding to conventional alloy 625. Furthermore, a nickel-based alloy of the present invention similar to Heat 6 described above was prepared and designated as Heat 10, which is also listed in Table 2. The composition of Heat 10 is Ni:43.48, Cr:22.00, Fe:24.95, Mo:5.72, Mn:0.17, Si:0.40, Cu:0.97, N:0.05, W:0.066, Co:2.00, Ti:0.001, B:0.0007, P:0.006, S:0.0002, Nb:0.093, Al:0.060, C:0.006, and V:0.029 (weight%). Heat 10 has a PREN of 41.7, N v The values ​​were 2.260 for and 0.862 for Metal-d.

[0073] In this example, all tests were conducted using cold-rolled and annealed 0.060-inch (1.5 mm) plates, except for the Charpy impact test, which used hot-rolled and annealed 0.270-inch (6.85 mm) plates. All materials were hot-rolled and cold-rolled, followed by solution annealing (SA) at 2100°F (1150°C) for a time corresponding to the thickness. Some materials were also subjected to a simulated post-cladding heat treatment (PCHT), consisting of a first stage at 1750°F (954°C) followed by a second stage at 1100°F (593°C). Tests were conducted on samples in both the SA and PCHT states.

[0074] Charpy impact tests were performed in accordance with ASTM (American Society for Testing and Materials (ASTM) International, 100 Barr Harbor Drive, West Conshohocken, PA, 19428) E23 (Standard Test Method for Notched Bar Impact Testing of Metallic Materials) (West Conshohocken, PA: ASTM)). Half-size (0.197 inch [5 mm]) Charpy samples were machined from a 0.270 inch plate and tested at -58°F (-50°C). For each alloy, two samples were tested: one in the solution annealed state and one in the PCHT state. Samples were prepared in the width direction (TL). After testing, the impact absorption energy, elongation in the width direction, and shear fracture rate were reported.

[0075] Tensile tests were performed at room temperature in accordance with ASTM E8 (latest version) "Standard Test Methods for Tensile Testing of Metallic Materials (West Conshohocken, PA: ASTM)". Standard gauge length 2-inch (50.8 mm) tensile specimens were prepared longitudinally from 0.060-inch (1.5 mm) material. Three specimens were tested for each alloy in each state, and the 0.2% offset yield strength, ultimate tensile strength, and % elongation were determined.

[0076] The critical pitting temperature (CPT) for each alloy was measured using specimens according to ASTM G48 (West Conshohocken, PA: ASTM) Method C, standard test method for pitting and crevice corrosion resistance of stainless steel and related alloys using ferric chloride solution (West Conshohocken, PA). Specimens measuring approximately 1 inch × 2 inches (25 mm × 50 mm) were sheared from a 0.060 inch sheet. The sheared edges were ground, deburred, and finished with 240-grit sandpaper. The specimens were cleaned with distilled water and acetone, and two specimens were tested at each temperature. The specimens were immersed in an acidified ferric chloride solution, and the test was repeated until the CPT was reached, with the solution temperature increased in 5°C (9°F) increments. CPT is defined as the lowest temperature at which pits greater than 0.001 inches (0.025 mm) in depth are formed.

[0077] Intergranular corrosion resistance was measured using Method A of ASTM G28 (latest version) "Standard Test Method for the Detection of Intergranular Corrosion Susceptibility of Forged Nickel-Rich, Chromium-Bearing Alloys (West Conshohocken, PA: ASTM)". Two specimens measuring approximately 1 inch x 2 inches (25 mm x 50 mm) were sheared from a 0.060 inch sheet. The sheared edges were ground, deburred, and finished with 240 grit sandpaper. The specimens were washed with distilled water and acetone and immersed in a boiling ferric sulfate-sulfuric acid solution. The test was conducted for 120 hours, and the weight loss of each specimen was determined.

[0078] Stress corrosion cracking resistance was determined in a boiling magnesium chloride solution in accordance with ASTM G36 (latest version) "Six standard tests for evaluating the stress corrosion cracking resistance of metals and alloys in boiling magnesium chloride solution (West Conshohocken, PA: ASTM)". Two 1-inch x 4-inch (25.4 x 101.6 mm) test specimens were sheared from 0.060-inch (1.5 mm) sheets of each alloy. The sheared edges were ground and deburred and finished with 240-grit sandpaper. Two 0.5-inch (12.7 mm) holes were drilled from each end, and the specimens were then immersed in a 20% HNO3 solution at 130°F (54°C) for 10 minutes to remove contaminants, and rinsed with distilled water. The specimens were then bent into a U-shape around a 1-inch (25.4 mm) diameter. This creates a stress state similar to that commonly experienced in the field as a result of equipment manufacturing (welding, forming), installation, and operation (temperature gradient). The ends of the U-shaped bent specimens were then bolted together, maintaining a 1-inch (25.4 mm) spacing between the legs, and the specimens were insulated from the bolts using plastic washers. The assemblies were cleaned ultrasonically and then immersed in boiling 45% MgCl2 at 155°C (311°F). The U-shaped bent specimens were periodically checked for cracks. The test was continued until cracks appeared or the immersion time reached 1,008 hours.

[0079] Several 11-inch (279 mm) bead-on-plate welds were fabricated on 0.060-inch (1.5 mm) Heat 6 alloy plates using 625 alloy filler metal, specifically ERNiCrMo-3, 3 / 32” (2.4 mm) welding wire. Welding was performed using the gas tungsten arc welding (GTAW) method. Argon was used as the shielding and backing gas. The power settings were 70 amps, 10.5 volts. To check the integrity of the weld, the welded specimens were bent 180 degrees around a 1.5-inch (38 mm) diameter die while tension was applied to the weld surface. To examine the microstructure of the weld, the cross-section of the weld was polished and etched with a mixed acid etching solution.

[0080] The results of mechanical and corrosion tests on Heat 6 alloy were compared with the results of similar tests performed on Heat C5, Heat C6, and Heat C7 alloys (N08367).

[0081] Table 3 shows the results of tensile tests performed on 0.060-inch (1.5 mm) material in solution annealed and PCHT states. The mechanical property test results are shown graphically in Figures 18-21. The solution annealing temperature of 2100°F (1150°C) was chosen to ensure complete solution treatment for all tested alloys. Therefore, the strengths were lower than those typically obtained when annealed at lower temperatures. The fact that the tensile properties of Heat 6 alloy and Heat C6 alloy showed no noticeable change after PCHT is highly significant. However, the strength of Heat C5 alloy increased substantially. This is thought to be due to the precipitation of undesirable intermetallic compounds during PCHT. [Table 3]

[0082] Table 4 shows the results of Charpy impact tests conducted at -58°F (-50°C) on 0.197-inch (5 mm) samples oriented in the width direction (TL). The Charpy impact energy test results are shown graphically in Figure 22. The samples were tested after solution annealing at 2100°F (1150°C) and two-stage PCHT at 1750°F (954°C) and 1100°F (593°C). This data indicates that all samples had 100% shear fracture surfaces and no cleavage fracture regions. Furthermore, the lateral expansion of all fractured samples was also quite large, ranging from 39 to 60 mils (1.0 to 1.5 mm). However, there were significant differences in absorbed energy between alloys. [Table 4]

[0083] In the solution-annealed state, Heat 6, Heat C6 (825 alloy), and Heat C5 (6Mo alloy) all absorbed similar amounts of energy, but Heat C7 (625 alloy) absorbed less energy. After PCHT, there was virtually no change in the amount of energy absorbed by Heat 6 and Heat 7 alloys, but the amount of energy absorbed by the other alloys decreased significantly. This difference in behavior can be explained by the improved phase stability of Heat 6 alloy. The precipitation of harmful phases during PCHT embrittles a portion of the alloy, reducing the amount of energy absorbed during fracture.

[0084] To support the Charpy impact test results and to confirm the presence of harmful phases in several reference alloys, metallographic analysis was performed on the cross-sections of the fractured impact test specimens. After placing and polishing the metallographic specimens, electrolytic etching was performed in oxalic acid at a potential of 6V for 90 seconds. Figure 1 shows a comparison of the microstructures of Heat 6 alloy and Heat C5 alloy in the solution annealed and PCHT states. Although several particles are observed in the microstructure of Heat 6 alloy, there is little to no precipitation at the grain boundaries, and no significant changes are seen after PCHT.

[0085] The microstructural stability of the Heat 6 alloy is in contrast to that of the Heat C5 alloy, where the grain boundaries are brightly etched in the solution annealing state, but deeply etched in the PCHT state. This indicates that the microstructural structure of the Heat C5 alloy was unstable during PCHT. The Charpy test results showed that the absorbed energy of the Heat C5 alloy decreased from 125 foot-pounds (169 J) to 69 foot-pounds (94 J), which is thought to be due to the precipitation of harmful phases at the grain boundaries. The increase in tensile strength after PCHT, shown in Table 2, is also thought to be due to the same reason.

[0086] Table 5 shows the critical pitting temperatures for Heat 6 alloy and other alloys, measured in solution annealing and PCHT states according to ASTM G48 Method C. The results for critical pitting temperatures are shown graphically in Figure 23. [Table 5]

[0087] The results correspond to the PREN number of the alloys. Heat C7 showed the highest CPT among the tested alloys because it contains a large amount of Mo, which is generally considered excess in many aqueous environments. Heat C7 alloy did not develop pitting corrosion in the 80°C (176°F) test, so its CPT is at least 85°C (185°F). Since 85°C (185°F) is the maximum temperature for this test in the ASTM G48 Method C test procedure, no tests were performed at temperatures higher than this. Heat C5 alloy had the second highest PREN and the second highest CPT of 75°C (167°F). Heat 6 alloy had a CPT of 50°C (122°F), while Heat C6 alloy had a CPT of 35°C (93°F), indicating that Heat 6 alloy has a significantly higher CPT than Heat C6 alloy.

[0088] As seen in Figures 4 and 5, PCHT precipitated harmful phases, but unexpectedly, it did not reduce the CPT of the heat-treated C5 alloy or any other alloy. This is thought to be because there were no Cr-deficient regions near these precipitates. With two-stage PCHT, reverse diffusion of Cr becomes possible after precipitate formation, and it is possible to restore corrosion resistance even when mechanical properties have clearly deteriorated due to grain boundary precipitates.

[0089] Table 6 shows the results of intergranular corrosion rates of Heat 6 alloy and other alloys, measured according to ASTM G28 Method A. The intergranular corrosion rates are shown graphically in Figure 24. The rates are expressed in mills / year and mm / year. [Table 6]

[0090] All alloys tested exhibited fairly low corrosion rates in the solution-annealed state. Heat 6 and Heat C6 alloys showed the lowest rates, while Heat C5 and Heat C7 alloys were slightly higher. The common acceptance criterion used for 625 alloy (Heat C7) in this test was a corrosion rate of less than 0.625 mm / year (24.6 mpy), and all alloys tested easily met this requirement in the solution-annealed state. In this test, the corrosion rate of most alloys increased after PCHT. The corrosion rate was 6.5% higher for Heat 6 alloy, 19.4% higher for Heat C6 alloy, and 44.1% higher for Heat C5 alloy. Heat C7 alloy was 8.3% lower. Except for Heat C5 alloy, all these differences were small, and even that alloy's corrosion rate was considerably lower than the target limit of 0.625 mm / year (24.6 mpy).

[0091] Table 7 shows the measurement results of the time to SCC fracture for two samples of Heat 6 alloy and another alloy, tested according to ASTM G36. The results of stress corrosion cracking are shown graphically in Figure 25. [Table 7] This test is significant in identifying the expected performance of alloys under stress from the manufacture, installation, and operation of equipment. The test was terminated if no cracks occurred after 1,008 hours. The data shows that both Heat 6 and Heat C7 alloys passed the test, with no cracks observed. The 625 alloy (Heat 7), containing 63% Ni, was expected to perform well in this test. The relationship between chloride stress corrosion cracking susceptibility and Ni content was demonstrated by H.R. Copson ("Effect of Composition on Stress Corrosion Cracking of Some Alloys Containing Nickel," Physical Metallurgy of Stress Corrosion Fracture, Interscience Publishers, New York, 1959). In the alloys shown in Table 6, the time to failure increased with increasing Ni content. From these results, it can be concluded that Heat 6 alloy has a sufficient Ni content to withstand SCC under the stress of a boiling, high-chloride environment at 155°C, more so than 825 alloy (Heat C6) or super austenitic stainless steel. It is also important to note that, with the exception of Heat C5 alloy, no significant decrease in SCC resistance was shown by PCHT. The decrease in the resistance of these alloys is thought to be due to the large-scale precipitation of harmful phases in the alloy during PCHT, as shown in Figures 4 and 5.

[0092] The Heat 6 alloy sample was welded using GTAW welding with 625 alloy filler metal. An optical microscope image of the weld at approximately 100x magnification is shown in Figure 26. To check the integrity of the weld, the weld surface was bent 180 degrees around a 1.5-inch (38 mm) diameter die while under tension. To examine the microstructure of the weld, the cross-section of the weld was polished and etched with a mixed acid etching solution. Figure 12 shows the microstructure after welding at the interface between the weld and the base metal. Although there is a small mixed region at the interface, there is almost no precipitation of harmful phases in the region adjacent to the weld. In the bending test of the weld surface, no visible cracks were observed, and it showed good ductility.

[0093] The Heat 6 alloy and other alloys of the present invention have a very stable microstructure that is less prone to the formation of harmful phases even when exposed to sensitizing heat treatments, such as those applied to hot-rolled jointed pipes after cladding. As a result, the simulated mechanical properties after PCHT, particularly impact toughness, remain largely unchanged.

[0094] The corrosion resistance of the nickel-based alloy of the present invention remained largely unchanged after PCHT, which was not the case for other alloys tested, particularly the Heat C5 alloy. The Heat 6 alloy, with a PREN of 42 and a CPT of 50°C (122°F), exhibited superior pitting corrosion resistance in chloride-containing environments such as seawater compared to the 825 alloy (Heat C6). The Heat 6 alloy remained crack-free for over 1000 hours in a boiling MgCl2 solution, exceeding the performance of the 825 alloy (Heat C6) and the Heat C5 alloy in the same test. The Heat 6 alloy also showed good resistance to intergranular corrosion after sensitizing heat treatment.

[0095] We successfully welded sheets of Heat 6 alloy using 625 alloy filler material. The welded specimens passed bending tests without cracking, and the microstructure of the weld and the heat-affected zone adjacent to the weld was sound.

[0096] These test results, taken together, demonstrate that the nickel-based alloys of the present invention, including Heat 6 alloy, offer cost-saving benefits as an alternative to alloy 625 in harsh corrosive environments, such as those found in applications in petroleum and gas processing and chemical processing. The nickel-based alloys of the present invention can provide an improvement over alloy 825 in applications requiring even greater corrosion resistance.

[0097] <Modes of the Invention> Various aspects of the present invention include, but are not limited to, the following numbered sections. 1. Nickel-based alloys containing 38-60 wt% Ni, 19-25 wt% Cr, 15-35 wt% Fe, 3-7 wt% Mo, and 0.1-10 wt% Co. 2. The nickel-based alloy according to item 1, comprising 39-50% by weight of Ni, 20-25% by weight of Cr, 15-30% by weight of Fe, 3.5-6.5% by weight of Mo, and 0.2-4% by weight of Co. 3. A nickel-based alloy according to item 1 or 2, comprising 40-48% by weight of Ni, 21-25% by weight of Cr, 16-29% by weight of Fe, 4-6.5% by weight of Mo, and 0.25-2.6% by weight of Co. 4. A nickel-based alloy according to any one of items 1 to 3 above, further comprising 0.1 to 4 wt% Cu and 0.1 to 3 wt% Mn. 5. A nickel-based alloy according to any one of items 1 to 4 above, further comprising less than 0.15 wt% N, less than 1.0 wt% Si, 0.01 to 0.1 wt% Ti, 0.01 to 0.2 wt% Nb, 0.02 to 0.3 wt% Al, and 0.0002 to 0.005 wt% B. 6. A nickel-based alloy according to any one of items 1 to 4 above, further comprising 0.2 to 3 wt% Cu and 0.2 to 2.5 wt% Mn. 7. A nickel-based alloy according to any one of items 1 to 6 above, further comprising less than 0.15 wt% N, less than 1.0 wt% Si, 0.01 to 0.08 wt% Ti, 0.02 to 0.15 wt% Nb, 0.04 to 0.25 wt% Al, and 0.0004 to 0.0035 wt% B. 8. A nickel-based alloy according to any one of items 1 to 4 above, further comprising 0.25 to 2 wt% Cu and 0.25 to 2 wt% Mn. 9. A nickel-based alloy according to any one of items 1 to 8, further comprising less than 0.15 wt% N, less than 1.0 wt% Si, 0.01 to 0.07 wt% Ti, 0.02 to 0.1 wt% Nb, 0.06 to 0.25 wt% Al, and 0.0010 to 0.0030 wt% B. 10. The nickel-based alloy is any one of items 1 to 9 above, wherein the nickel-based alloy contains less than 0.01% by weight of Mg. 11. The nickel-based alloy further comprises 0.01 to 0.1 wt% Ti, and any of the nickel-based alloys described in items 1 to 10 above. 12. The nickel-based alloy according to any one of items 1 to 11, wherein the nickel-based alloy contains less than 0.3% by weight of V. 13. The nickel-based alloy is any one of items 1 to 12, wherein the nickel-based alloy contains less than 0.3% by weight of W. 14. The nickel-based alloy is any one of items 1 to 13 above, and contains 0.010% by weight or less of C. 15. The nickel-based alloy according to any one of items 1 to 14, wherein the nickel-based alloy has at least 40 PREN. 16. The nickel-based alloy having PREN of 40 to 45, the nickel-based alloy according to any one of items 1 to 15 above. 17. A nickel-based alloy according to any one of paragraphs 1 to 16 and 18 to 20, wherein the nickel-based alloy has a Charpy impact energy of at least 100 foot-pounds, as measured using a 5 mm specimen at -50°C in accordance with ASTM E23-18. 18. A nickel-based alloy according to any one of items 1 to 17, 19, and 20, wherein the nickel-based alloy has a critical pitting temperature greater than 95°F as measured in accordance with ASTM G48 Method C. 19. A nickel-based alloy according to any one of items 1 to 18 and 20, wherein the nickel-based alloy has an intergranular corrosion rate of less than 0.25 mm / year as measured in accordance with ASTM G28 Method A. 20. The nickel-based alloy according to any one of items 1 to 19, wherein the stress corrosion cracking resistance measured in accordance with ASTM G36 is more than 1,000 hours. 21. The nickel-based alloy according to any one of items 1 to 20, wherein the nickel-based alloy is subjected to post-cladding heat treatment. 22. The nickel-based alloy according to item 21, wherein the nickel-based alloy after the post-cladding heat treatment has a sigma solvus of less than 2,000°F. 23. The nickel-based alloy according to item 22, wherein the sigma solvus is 1,846 to 1,996°F. 24. The nickel-based alloy after the post-cladding heat treatment has an N v less than 2.4. The nickel-based alloy according to any one of items 21 to 23. 25. The N v is 2.154 to 2.331. The nickel-based alloy according to item 24. 26. The nickel-based alloy after the post-cladding heat treatment has a metal d less than 0.87. The nickel-based alloy according to any one of items 21 to 25. 27. The nickel-based alloy according to item 26, wherein the metal d is 0.852 to 0.865. 28. The nickel-based alloy after the post-cladding heat treatment has a Charpy impact energy of at least 100 foot-pounds measured using a 5 mm test piece at -50°C in accordance with ASTM E23-18. The nickel-based alloy according to any one of items 21 to 27. 29. The nickel-based alloy according to item 28, wherein the Charpy impact energy is at least 110 foot-pounds. 30. The nickel-based alloy according to any one of items 1 to 29, wherein the Charpy impact energy of the nickel-based alloy in the state after post-cladding heat treatment is at least 85% of the Charpy impact energy of the alloy in the solutionized and annealed state. 31. The nickel-based alloy according to any one of paragraphs 1 to 29, wherein the Charpy impact energy in the state after cladding and heat treatment is at least 90% of the Charpy impact energy of the alloy in the state after solution annealing. 32. A nickel-based alloy according to any one of items 21 to 31, wherein the Charpy impact energy of the nickel-based alloy in the cladded and heat-treated state, measured at -50°C using a 5 mm specimen in accordance with ASTM E23-18, is greater than or equal to the Charpy impact energy of the alloy in the solution-annealed state. 33. A nickel-based alloy that has undergone post-cladding heat treatment and has a critical pitting temperature greater than 95°F as measured in accordance with ASTM G48 Method C, according to any one of items 21-32, 34, and 35 above. 34. A nickel-based alloy according to any one of items 21-33 and 35, wherein the nickel-based alloy, after cladding and heat treatment, has an intergranular corrosion rate of less than 0.25 mm / year as measured in accordance with ASTM G28 Method A. 35. A nickel-based alloy according to any one of paragraphs 21 to 34 above, wherein the nickel-based alloy, after cladding and heat treatment, has a stress corrosion cracking resistance of more than 1,000 hours as measured in accordance with ASTM G36. 36. A method for producing a nickel-based alloy, wherein the nickel-based alloy comprises 38-60% by weight of Ni, 19-25% by weight of Cr, 15-35% by weight of Fe, 0.1-10% by weight of Co, and 3-7% by weight of Mo. Homogenizing nickel-based alloy ingots, The process involves processing a homogenized ingot to form a slab or billet, Further hot rolling is performed to produce plate-shaped, rod-shaped, or tubular products. The aforementioned product is annealed, and A method comprising cooling the annealed product. 37. The method according to item 36, further comprising subjecting the product to post-cladding heat treatment or a weld heat-affected zone. 38. The method of paragraph 37, wherein the post-cladding heat treatment is carried out at a temperature of 1,100 to 1,800°F. 39. The method of paragraph 37 or 38, wherein the post-cladding heat treatment is performed at a first temperature and / or a second temperature lower than the first temperature. 40. The post-cladding heat-treated product is subjected to any one of the methods of paragraphs 37 to 39, wherein the sigma sorbus is less than 2,000°F. 41. Products heat-treated after cladding must have a N content of less than 2.4. v A method according to any one of the above paragraphs 37 to 40, having the following characteristics. 42. The method according to any one of paragraphs 37 to 41, wherein the post-cladding heat-treated product has a metal d of less than 0.87. 43. The post-cladding heat-treated product has a Charpy impact energy of at least 100 foot-pounds, as measured using a 5 mm specimen at -50°C in accordance with ASTM E23-18, by any one of the methods of paragraphs 37 to 42. 44. The method according to any one of paragraphs 37 to 43, wherein the nickel-based alloy has a Charpy impact energy in a state after cladding and heat treatment that is at least 85% of the Charpy impact energy of the alloy in a solution-annealed state. 45. The nickel-based alloy according to any one of paragraphs 37 to 44, wherein the Charpy impact energy in the cladding-heat-treated state is at least 90% of the Charpy impact energy of the alloy in the solution-annealed state. 46. ​​A nickel-based alloy according to any one of sections 37-45 and 47-49, wherein the Charpy impact energy of the nickel-based alloy in the cladded and heat-treated state, measured at -50°C using a 5 mm specimen in accordance with ASTM E23-18, is greater than or equal to the Charpy impact energy of the alloy in the solution-annealed state. 47. A nickel-based alloy that has been heat-treated after cladding, having a critical pitting temperature greater than 95°F as measured in accordance with ASTM G48 Method C, according to any one of items 37-46, 48, and 49. 48. A nickel-based alloy according to any one of paragraphs 37-47 and 49, wherein the nickel-based alloy, after cladding and heat treatment, has an intergranular corrosion rate of less than 0.25 mm / year as measured in accordance with ASTM G28 Method A. 49. A nickel-based alloy according to any one of paragraphs 37 to 48, wherein the nickel-based alloy, after cladding and heat treatment, has a stress corrosion cracking resistance of more than 1,000 hours as measured in accordance with ASTM G36.

[0098] Any patents, patent applications, publications, or other external documents identified herein are incorporated herein in their entirety by reference unless otherwise specified, but only to the extent that the incorporated material does not contradict the descriptions, definitions, representations, illustrations, etc. To this end, to the extent necessary, the explicit descriptions contained herein take precedence over any conflicting material incorporated by reference. Any material or part thereof incorporated herein by reference that contradicts the explicit descriptions contained herein shall be incorporated only to the extent that there is no conflict between the incorporated material and the explicit descriptions. The applicant reserves the right to amend this specification to explicitly describe any subject matter or part thereof incorporated by reference. Any amendment to this specification to add such incorporated subject matter shall conform to the description requirements (e.g., 35 U.S. SC § 112(a) and EPC § 123(2)).

[0099] Various features and characteristics are described herein and illustrated in the drawings to provide an overall understanding of the present invention. It is understood that the various features and characteristics described herein and illustrated in the drawings can be combined in any way, whether such features and characteristics are expressly described or illustrated herein. The inventors and applicants expressly intend that such combinations of features and characteristics are included within the scope of this specification, and further intend that any claim of such combinations of features and characteristics does not add new subject matter to this application. Therefore, the claims may be amended to reference any combination of features and characteristics expressly or essentially described herein, or other features and characteristics that are expressly or essentially supported. The applicant also reserves the right to amend the claims to positively waive any features or characteristics that may exist in the prior art, even if they are not expressly described herein. Therefore, such amendments do not add new matter to the specification or claims and comply with the description requirements and additional matter requirements (e.g., 35 U.S. SC § 112(a) and EPC § 123(2)). The present invention includes, and may consist of, or be essentially composed of, the various features and properties described herein. In some cases, the present invention may substantially not include any of the components or other features or properties described herein.

[0100] Furthermore, the numerical ranges described herein include the specified endpoints and describe all subranges of the same numerical precision (i.e., the same number of digits) contained within the specified range. For example, the range "1.0 to 10.0" is the range between (and including) the minimum value of "1.0" and the maximum value of "10.0," and even if the range "2.4 to 7.6" is not explicitly described, it is considered to be described as "2.4 to 7.6," etc. Accordingly, the applicant reserves the right to amend this specification, including the claims, to explicitly describe any subrange of the same numerical precision that is included within the ranges explicitly described herein. All such ranges are essentially described herein, and amending to explicitly describe such any subranges would comply with the description requirements and additional requirements (e.g., 35 U.S. SC § 112(a) and EPC § 123(2)).

[0101] As used herein, “including,” “containing,” and similar terms are synonymous with “comprising” in the context of this specification. Therefore, these terms are open-ended and are understood not to exclude the existence of undescribed or unspecified materials, components, or process steps. As used herein, “consisting of” is understood not to exclude the existence of unspecified elements, components, or process steps. As used herein, “consisting essentially of” is understood not to exclude the existence of unspecified elements, components, or process steps, but to include elements, materials, components, or process steps that include the specified elements, components, or process steps and do not substantially affect the basic and novel properties described. As used herein, the grammatical articles “one,” “a,” “an,” and “the” are intended to include “at least one” or “more than one,” unless otherwise indicated or required by context. Therefore, the articles as used herein refer to one or more grammatical objects of the article (i.e., “at least one”). For example, “a component” means one or more components, and therefore more than one components are intended and can be adopted or used in the implementation of the present invention. Furthermore, the use of a singular noun includes the plural form, and the use of a plural noun includes the singular form unless otherwise required by the context of use.

[0102] While specific embodiments of the present invention have been described in detail, those skilled in the art will understand that various modifications and substitutions can be made to those details in light of the overall teachings of the invention herein. Accordingly, the specific embodiments described are for illustrative purposes only and do not necessarily limit the scope of the invention to be given to the entire scope of the claims and all its equivalents.

Claims

1. A nickel-based alloy comprising 38 to 60% by weight of Ni, 19 to 25% by weight of Cr, 15 to 35% by weight of Fe, 3 to 7% by weight of Mo, more than 0.5% by weight and up to 5.0% by weight of Co, 0.1 to 4% by weight of Cu, and 0.1 to 3% by weight of Mn, and optionally comprising 0.03% by weight or less of C, 0.15% by weight or less of N, 1.0% by weight or less of Si, 0.1% by weight or less of Ti, 0.2% by weight or less of Nb, 0.3% by weight or less of Al, 0.005% by weight or less of B, 0.3% by weight or less of V, 0.3% by weight or less of W, and 0.01% by weight or less of Mg, with the remainder being incidental impurities, wherein the nickel-based alloy is It has the characteristic of having a Charpy impact energy of at least 100 foot-pounds, measured using a 5 mm specimen at -50°C in accordance with ASTM E23-18, and also has the following characteristics: Characteristics where the critical pitting temperature measured in accordance with ASTM G48 Method C is greater than 95°F. Characteristics of having an intergranular corrosion rate of less than 0.25 mm / year, as measured in accordance with ASTM G28 Method A, and The characteristic of having stress corrosion cracking resistance exceeding 1,000 hours, as measured in accordance with ASTM G36. A nickel-based alloy having at least one of the following properties.

2. The nickel-based alloy according to claim 1, comprising 39 to 50% by weight of Ni, 20 to 25% by weight of Cr, 15 to 30% by weight of Fe, 3.5 to 6.5% by weight of Mo, and more than 0.5% by weight and up to 4% by weight of Co.

3. The nickel-based alloy according to claim 1, comprising 40 to 48% by weight of Ni, 21 to 25% by weight of Cr, 16 to 29% by weight of Fe, 4 to 6.5% by weight of Mo, and more than 0.5% by weight and less than or equal to 2.6% by weight of Co.

4. The nickel-based alloy according to claim 1, comprising less than 0.15% by weight of N, less than 1.0% by weight of Si, 0.01 to 0.1% by weight of Ti, 0.01 to 0.2% by weight of Nb, 0.02 to 0.3% by weight of Al, and 0.0002 to 0.005% by weight of B.

5. The nickel-based alloy according to claim 1, comprising 0.2 to 3% by weight of Cu and 0.2 to 2.5% by weight of Mn.

6. The nickel-based alloy according to claim 5, comprising less than 0.15% by weight of N, less than 1.0% by weight of Si, 0.01 to 0.08% by weight of Ti, 0.02 to 0.15% by weight of Nb, 0.04 to 0.25% by weight of Al, and 0.0004 to 0.0035% by weight of B.

7. The nickel-based alloy according to claim 1, comprising 0.25 to 2% by weight of Cu and 0.25 to 2% by weight of Mn.

8. The nickel-based alloy according to claim 7, comprising less than 0.15% by weight of N, less than 1.0% by weight of Si, 0.01 to 0.07% by weight of Ti, 0.02 to 0.1% by weight of Nb, 0.06 to 0.25% by weight of Al, and 0.0010 to 0.0030% by weight of B.

9. The nickel-based alloy according to claim 1, wherein the nickel-based alloy contains less than 0.01% by weight of Mg.

10. The nickel-based alloy according to claim 9, wherein the nickel-based alloy contains 0.01 to 0.1% by weight of Ti.

11. The nickel-based alloy according to claim 1, wherein the nickel-based alloy contains less than 0.3% by weight of V.

12. The nickel-based alloy according to claim 1, wherein the nickel-based alloy contains less than 0.3% by weight of W.

13. The nickel-based alloy according to claim 1, wherein the nickel-based alloy contains 0.010% by weight or less of C.

14. The nickel-based alloy according to claim 1, wherein the nickel-based alloy has at least 40 PREN.

15. The nickel-based alloy according to claim 1, wherein the nickel-based alloy has 40 to 45 PREN.

16. The nickel-based alloy according to claim 1, wherein the nickel-based alloy has a Charpy impact energy of at least 100 foot-pounds, as measured using a 5 mm specimen at -50°C in accordance with ASTM E23-18.

17. The nickel-based alloy according to claim 1, wherein the nickel-based alloy has a critical pitting temperature greater than 95°F, as measured in accordance with the ASTM G48 Method C.

18. The nickel-based alloy according to claim 1, wherein the intergranular corrosion rate measured in accordance with ASTM G28 Method A is less than 0.25 mm / year.

19. The nickel-based alloy according to claim 1, wherein the nickel-based alloy has a stress corrosion cracking resistance of more than 1,000 hours as measured in accordance with ASTM G36.

20. The nickel-based alloy according to claim 1, wherein the nickel-based alloy is subjected to a heat treatment equivalent to a post-cladding heat treatment.

21. The nickel-based alloy according to claim 20, wherein the nickel-based alloy after the heat treatment has a sigma sorbus of less than 2,000°F.

22. The nickel-based alloy according to claim 21, wherein the sigma solubus is 1,846 to 1,996°F.

23. The nickel-based alloy subjected to the aforementioned heat treatment is N ｖ The nickel-based alloy according to claim 20, wherein is less than 2.

4.

24. The aforementioned N ｖ The nickel-based alloy according to claim 23, wherein the ratio is 2.154 to 2.

331.

25. The nickel-based alloy according to claim 20, wherein the heat-treated nickel-based alloy has a metal d of less than 0.

87.

26. The nickel-based alloy according to claim 25, wherein the metal d is 0.852 to 0.

865.

27. The nickel-based alloy according to claim 20, wherein the heat-treated nickel-based alloy has a Charpy impact energy of at least 100 foot-pounds, as measured using a 5 mm specimen at -50°C in accordance with ASTM E23-18.

28. The nickel-based alloy according to claim 27, wherein the Charpy impact energy is at least 110 foot-pounds.

29. The nickel-based alloy according to claim 20, wherein the Charpy impact energy of the nickel-based alloy in the heat-treated state is at least 85% of the Charpy impact energy of the alloy in the solution-annealed state.

30. The nickel-based alloy according to claim 20, wherein the Charpy impact energy of the nickel-based alloy in the heat-treated state is at least 90% of the Charpy impact energy of the alloy in the solution-annealed state.

31. The nickel-based alloy according to claim 20, wherein the Charpy impact energy measured at -50°C using a 5 mm test specimen in accordance with ASTM E23-18 is greater than or equal to the Charpy impact energy of the nickel-based alloy in the heat-treated state compared to the Charpy impact energy of the alloy in the solution-annealed state.

32. The nickel-based alloy according to claim 20, wherein the heat-treated nickel-based alloy has a critical pitting temperature greater than 95°F, as measured in accordance with ASTM G48 Method C.

33. The nickel-based alloy according to claim 20, wherein the heat-treated nickel-based alloy has an intergranular corrosion rate of less than 0.25 mm / year, as measured in accordance with ASTM G28 Method A.

34. The nickel-based alloy according to claim 20, wherein the heat-treated nickel-based alloy has a stress corrosion cracking resistance of more than 1,000 hours as measured in accordance with ASTM G36.

35. A method for producing nickel-based alloys, The nickel-based alloy contains 38 to 60% by weight of Ni, 19 to 25% by weight of Cr, 15 to 35% by weight of Fe, more than 0.5% by weight and up to 5.0% by weight of Co, 3 to 7% by weight of Mo, 0.1 to 4% by weight of Cu, and 0.1 to 3% by weight of Mn, and optionally contains 0.03% by weight or less of C, 0.15% by weight or less of N, 1.0% by weight or less of Si, 0.1% by weight or less of Ti, 0.2% by weight or less of Nb, 0.3% by weight or less of Al, 0.005% by weight or less of B, 0.3% by weight or less of V, 0.3% by weight or less of W, and 0.01% by weight or less of Mg, with the remainder being incidental impurities, and the method is as follows: Homogenizing the nickel-based alloy ingot, The homogenized ingot is processed to form a slab or billet, Further hot rolling is performed to produce plate-shaped, rod-shaped, or tubular products. Annealing the aforementioned product, and This includes cooling the annealed product, The aforementioned nickel-based alloy is It has the characteristic of having a Charpy impact energy of at least 100 foot-pounds, measured using a 5 mm specimen at -50°C in accordance with ASTM E23-18, and also has the following characteristics: Characteristics where the critical pitting temperature measured in accordance with ASTM G48 Method C is greater than 95°F. Characteristics of having an intergranular corrosion rate of less than 0.25 mm / year, as measured in accordance with ASTM G28 Method A, and A method having at least one of the following properties: stress corrosion cracking resistance measured in accordance with ASTM G36 for more than 1,000 hours.

36. The method according to claim 35, further comprising subjecting the product to a post-cladding heat treatment.

37. The method according to claim 36, wherein the post-cladding heat treatment is performed at a temperature of 1,100 to 1,800°F.

38. The method according to claim 37, wherein the post-cladding heat treatment is performed at a first temperature, and then at a second temperature lower than the first temperature.

39. The method according to claim 36, wherein the post-cladding heat-treated product has a sigma sorbus of less than 2,000°F.

40. The product heat-treated after cladding has a N content of less than 2.

4. ｖ The method according to claim 36, having the following characteristics.

41. The method according to claim 36, wherein the post-cladding heat-treated product has a metal d of less than 0.

87.

42. The method according to claim 36, wherein the post-cladding heat-treated product has a Charpy impact energy of at least 100 foot-pounds, as measured using a 5 mm specimen at -50°C in accordance with ASTM E23-18.

43. The method according to claim 36, wherein the Charpy impact energy of the nickel-based alloy in a state after cladding and heat treatment is at least 85% of the Charpy impact energy of the alloy in a solution-annealed state.

44. The method according to claim 36, wherein the Charpy impact energy of the nickel-based alloy in a state after cladding and heat treatment is at least 90% of the Charpy impact energy of the alloy in a solution-annealed state.

45. The method according to claim 36, wherein the Charpy impact energy measured using a 5 mm specimen at -50°C in accordance with ASTM E23-18 is greater than or equal to the Charpy impact energy of the nickel-based alloy in the cladded and heat-treated state, compared to the Charpy impact energy of the alloy in the solution-annealed state.

46. The method according to claim 36, wherein the post-cladding heat-treated product has a critical pitting temperature greater than 95°F, as measured in accordance with ASTM G48 Method C.

47. The method according to claim 36, wherein the product heat-treated after cladding has an intergranular corrosion rate of less than 0.25 mm / year, as measured in accordance with ASTM G28 Method A.

48. The method according to claim 36, wherein the product heat-treated after cladding has a stress corrosion cracking resistance of more than 1,000 hours as measured in accordance with ASTM G36.

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