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Incoloy
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Incoloy refers to a range of superalloys now produced by the Special Metals Corporation (SMC) group of companies and created with a trademark by the Inco company in 1952.[1] Originally Inco protected these alloys by patent.[2] In 2000, the SMC published a 61-page document entitled "High-Performance Alloys for Resistance to Aqueous Corrosion" highlighting Incoloy, as well as Monel and Inconel products, and their use in fluid environments such as sulfuric acid, hydrochloric acid, hydrofluoric acid, phosphoric acid, nitric acid, other acids as well as freshwater environments.[3]

Incoloy products are mostly chromium-based and mostly nickel-based, and designed for corrosion resistance as well as strength at high temperatures.

Incoloy alloys belong to the category of super austenitic stainless steels.[4] One advantage is that Incoloy alloys do not have to be heat treated after welding to restore the corrosion resistance.[2]

Types

[edit]

There are different alloys to resist particular chemical attacks or under specific circumstances: for example, the DS Incoloy is to be used in heat-treating furnaces with reactive atmospheres and many heat cycles.

Incoloy 020 "exhibits excellent corrosion resistance in chemical environments that contain sulfuric acid, chlorides, phosphoric acid and nitric acid."[5]

Incoloy 028 "is resistant to both acids and salts. The copper content makes it resistant to sulfuric acid."[6]

Incoloy 330 "exhibits good strength at high temperatures and good resistance to oxidation and reduction environments."[7]

Incoloy 800 "is capable of remaining stable and maintaining its austenitic structure even after long time exposures to high temperatures".[4]

Incoloy 803 is designed for sulfur-rich environments.[8]

Incoloy 825 is approved for use in heat exchanger tubes by ASTM B163, and approved for pressure vessel operating temperatures up to 525°C or up to 538°C. It "offers exceptional resistance to corrosion by sulfuric acid and phosphoric acid".[9]

Incoloy 908 "has high tensile strength, fatigue crack growth resistance, good weldability, metallurgical stability and ductility, high fracture and impact toughness, [and] low coefficient of thermal expansion... [Its] resistance to oxygen embrittlement... allows hot fabrication without cracking."[10]

Incoloy 907 "has high strength and low thermal expansion coefficient at temperatures up to 800°F."[11]

Incoloy 945X is designed for chlorine-rich environments.[12] Molybdenum adds crevice corrosion and pitting resistance to Incoloy 945.[13]

Incoloy MA956 is made by a mechanical alloying rather than a bulk-melting process; it was studied for space reactor components in the JIMO project. It is difficult to weld and needs to be heated to 200C for forming processes.[14] A special friction welding process has been developed for it.[15]

Compositions (percentages)

[edit]
Alloy name Fe Cr Al Ti C Y
2O
3		 Cu Mn Co Ni P Si S Mo Nb
020[5] 35 19-21 0 0 0 0 3-4 <2 0 32-38 0 <1 0 2-3 0
028[6] 29-40.4 26-28 0 0 0 0 ? <2.5 0 30-34 0 0 0 3-4 0
803[8] 29.435-42.64 25-29 0 0 0 0 0 <1.5 0 32-37 0 <1 0 0 0
945[13] balance 19.5-23 0.01-0.7 0.5-2.5 0.005-0.04 0 1.5-3 1 0 45-55 0.03 0.5 0.03 3-4 2.5-4.5
945X[12] balance 19.5-23 0.01-0.7 0.5-2.5 0.005-0.04 0 1.5-3 1 0 45-55 0.03 0.5 0.03 3-4 2.5-4.5
330[7] Fe 43 17-20 0 0 0 0 0 <2 0 34-37 0 * 0 0 0
825[9] Fe >22, ~33 19.5-23.5 <0.2 0.6-1.2 <0.05 0 1.5-3.0 <1.0 0 38-46 0 <0.5 <0.03 2.5-3.5 0
907[11] Fe 42 0 0.03 1.5 0 0 0 0 13 38 0 0.15 0 0 4.7
908[10] 35.588 - 44.6 3.75 - 4.5 0.75 - 1.25 1.2 - 1.8 <0.03 0 <0.5 <1 <0.5 47 - 51 <0.015 <0.5 <0.005 0 2.7-3.3
800[4] Fe >39.5 19-23 0 0 0 0 0 <1.5% 0 30-35 0 0 0 0 0
020 [16] Fe (~40%) 20 n/p n/p <0.07 n/p 3.5 <2.0 n/p 35 <0.045 <1.0 <0.035 2.5 about 1
DS [17] Fe (~40%) 18 n/p 0.2 0.1 nil 0.5 0.8-1.5 18 (Co+Ni 38) 18 (Co+Ni 38) n/p 2.3 0.03
MA956 [14] Fe (~75%) 20 4.75 0.4 <0.1 0.5 <0.15 <0.3 <0.3 <0.5 <0.02 n/p n/p

See also

[edit]

References

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Incoloy

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Incoloy is a trademarked family of austenitic -iron- superalloys developed by , engineered for exceptional high-temperature strength, corrosion resistance, and oxidation resistance in extreme environments. These alloys typically contain 30-45% , 19-23% , and significant iron content, along with additions like , , and to enhance specific properties such as pitting resistance and fabricability. Known for their versatility, Incoloy alloys maintain structural integrity and mechanical performance in aggressive conditions, including , acidic media, and temperatures up to 1100°C (2012°F), distinguishing them from standard stainless steels. The development of Incoloy alloys began in the late with the introduction of alloy 800 by the International Nickel Company (Inco), now part of Special Metals, to address the growing demand for materials in heat-treating and chemical processing equipment. Subsequent innovations expanded the family, including alloy 825 in 1952 for broader corrosion resistance in environments and alloy 925 in 1982 for high-strength applications in oilfield equipment. More recent additions, such as alloys 945 and 945X introduced in 2008-2009, incorporate age-hardening mechanisms to achieve yield strengths exceeding 860 MPa (125 ksi) while resisting sulfide stress cracking in sour oil and gas service. Key variants in the Incoloy lineup include /800H/800HT for thermal processing and nuclear applications, and 25-6HN for wet resistance in chemical plants, 909 for low in components, and 27-7MO as a super-austenitic grade with 7% for handling. These alloys are widely employed in industries such as power generation (e.g., tubes), oil and gas (e.g., downhole tubing and valves), (e.g., exhaust systems), and processing (e.g., reaction vessels and piping). Their fabricability allows for , , and similar to austenitic stainless steels, ensuring broad industrial adoption despite higher costs compared to conventional alloys.

Introduction and History

Definition and Characteristics

Incoloy is a trademarked family of nickel-iron-chromium superalloys engineered for superior high-temperature strength and exceptional resistance in aggressive environments, such as those involving oxidation, sulfidation, and aqueous media. These alloys maintain structural integrity and fabricability under demanding conditions, making them suitable for applications requiring durability in chemical processing and thermal systems. The originated with the International Nickel Company (Inco) in 1952 and is now owned by . A key distinguishing feature of Incoloy alloys compared to is their higher iron content, which reduces the proportion to enhance cost-effectiveness while preserving robust performance. This composition results in an austenitic that provides excellent thermal stability and resistance to stress-corrosion cracking. Incoloy alloys are often classified as super-austenitic stainless steels due to their enhanced resistance to pitting, , and general degradation in harsh settings. Compositions vary across the family, but many include significant (typically 25-50%), iron as a major component, and (often 19-25% in corrosion-focused alloys), with strategic additions of elements such as , , and to optimize specific properties like resistance to reducing or oxidizing acids. For instance, alloys like Incoloy 800 and 825 exemplify this family by balancing these elements for versatile high-performance use.

Development and Evolution

The Incoloy family of alloys was initially developed in the early 1950s by the International Company (Inco) to provide corrosion-resistant materials suitable for demanding applications in chemical processing and high-temperature environments, where traditional materials like stainless steels fell short in performance. Inco registered the Incoloy trademark in 1952 and secured early patents for these nickel-iron-chromium-based superalloys, emphasizing their enhanced resistance to oxidation and corrosive media compared to earlier alloys. The alloys evolved significantly through the and , with key variants addressing specialized needs; for instance, Incoloy alloy 800, introduced in the 1950s but widely adopted in the , was optimized for components requiring high-temperature strength and resistance to carburization. Similarly, Incoloy alloy 825, introduced in 1952, offered superior resistance to acids, such as sulfuric and phosphoric, in chemical processing equipment. Ownership of the Incoloy alloys transferred from Inco to following the acquisition of Inco Alloys International, enabling continued innovation into the and beyond, including the development of Incoloy 945X for high-strength applications in sour oil and gas wells. This evolution was driven by post-World War II industrial expansion in petrochemical refining and , where the need for materials outperforming stainless steels in aggressive, high-temperature conditions spurred advancements in alloy design. Special Metals further supported these developments through technical publications, such as the 2000 corrosion resistance handbook detailing Incoloy performance in aqueous and high-temperature corrosive environments.

Properties

Mechanical and Physical Properties

Incoloy alloys, a family of nickel-iron-chromium superalloys, exhibit a range of mechanical properties that provide high strength and ductility suitable for demanding environments. At room temperature, typical tensile strength for annealed Incoloy alloys such as 800 and 825 ranges from 550 to 800 MPa, with yield strength between 200 and 450 MPa and elongation of 30-60%, demonstrating good ductility. For high-temperature variants like Incoloy 800H, room-temperature tensile strength is approximately 780 MPa, yield strength 540 MPa, and elongation 22%. These properties vary by alloy form (e.g., plate, bar, tubing) and processing condition, with cold-worked forms showing higher strength but reduced elongation. At elevated temperatures, Incoloy alloys maintain significant strength. For instance, Incoloy 800 annealed material reaches tensile strengths up to 820 MPa at 540°C and 455 MPa at 760°C, though yield strength decreases to 307 MPa at the latter temperature. Incoloy 800H and 800HT are optimized for creep-rupture performance, offering rupture strengths of 121 MPa at 650°C and 50 MPa at 760°C for 100,000-hour exposure, far exceeding standard Incoloy 800 in prolonged high-heat service up to 1000°C. typically falls in the range of 130-200 Brinell (equivalent to Rockwell B 80-95), depending on and alloy variant. Fatigue resistance and impact toughness align with ASTM specifications for alloys, with Incoloy 825 showing excellent low-temperature impact strength down to cryogenic levels. Compared to carbon steels, Incoloy alloys provide superior strength retention and in high-temperature scenarios, where carbon steels soften rapidly above 500°C. Physical properties of Incoloy alloys support their use in cycling applications. Density is consistently around 7.94-8.14 g/cm³ across variants like , 825, and H. The melting range spans 1357-1400°C, enabling robust high-temperature processing. Thermal conductivity increases with temperature, from 11-13 W/m·K at 20-25°C to 19-32 W/m·K at 540-600°C for Incoloy 800 and 825. The coefficient of is 13-18 × 10⁻⁶/°C over 20-600°C, with values around 14 × 10⁻⁶/°C for Incoloy 800H in this range. Modulus of elasticity starts at 196 GPa at and drops to 157-162 GPa at 600°C. The following table summarizes representative room-temperature mechanical properties for select annealed Incoloy alloys:
AlloyTensile Strength (MPa)Yield Strength (MPa)Elongation (%)Hardness (BHN)
80055125060140
825690-772324-44136-45N/A
800H78054022130
These attributes stem from the balanced nickel-iron-chromium compositions that stabilize the austenitic structure under thermal stress.

Corrosion and Oxidation Resistance

Incoloy alloys exhibit superior resistance to pitting, , and , particularly in chloride-rich environments and acidic media such as sulfuric and phosphoric acids. This performance stems from their composition, which includes high content that mitigates chloride-induced , while enhances protection against localized pitting and crevice attacks in reducing conditions. For instance, Incoloy alloy 825 demonstrates excellent resistance to these forms of degradation in chloride-containing solutions and acids up to moderate concentrations and temperatures. The alloys' pitting resistance is quantified by a (PREN) typically ranging from 30 to 40, depending on the variant, which correlates with strong performance in aggressive media. Critical pitting temperatures exceed 50°C in 3% NaCl solutions for many Incoloy grades, indicating robust localized corrosion resistance under standard testing conditions like ASTM G48. Additionally, Incoloy alloys perform well in freshwater, , and alkaline solutions, with minimal degradation due to the formation of stable passive films; for example, alloy 27-7Mo shows excellent compatibility without significant pitting or cracking. Compliance with NACE MR0175 standards for sour service further validates their suitability in hydrogen sulfide-containing environments. At elevated temperatures, Incoloy alloys provide oxidation resistance up to approximately 1100°C through the formation of a protective layer on the surface, which acts as a barrier against further oxygen ingress. This layer, primarily Cr₂O₃, is stable in oxidative atmospheres and contributes to resistance against carburization and nitridation in high-temperature gases, as seen in alloys like Incoloy 800, where additions form stable nitrides to prevent embrittlement. Carburization resistance is particularly notable in applications, where the alloy maintains integrity in carbon-rich environments up to 1000°C. The underlying mechanisms for this corrosion and oxidation resistance rely on the stable austenitic microstructure, stabilized by , which ensures and prevents phase transformations that could compromise protective films. and additions promote the development of dense, adherent passive layers in aqueous media, repassivating localized breaches and inhibiting propagation of pits or crevices. Unlike some alloys, Incoloy variants require no post-weld to preserve these properties, as does not significantly alter the passive film integrity when proper techniques are employed.

Alloys and Compositions

Major Alloy Variants

Incoloy alloys encompass a family of nickel-iron-chromium superalloys engineered for enhanced performance in corrosive and high-temperature environments, with major variants tailored for specific industrial demands. These variants differ primarily in their optimization for thermal stability, resistance, or low , evolving from foundational alloys like 800 series to advanced formulations such as 945X for ultra-high strength applications. The Incoloy 800 series, including alloys 800 ( N08800), 800H ( N08810), and 800HT ( N08811), is designed for high-temperature oxidation and carburization resistance in and heat-treating processes. Alloy 800 serves as the base with general elevated-temperature service, while 800H and 800HT offer improved creep and rupture strength through controlled carbon content and annealing, meeting ASTM specifications such as B408 for rods and B409 for plates. Applications include furnace components like radiant tubes, muffles, and furnace tubing, where they maintain structural integrity up to 1100°C. Incoloy 825 (UNS N08825) provides enhanced resistance to acids, including sulfuric, phosphoric, and nitric, making it suitable for chemical processing and oilfield equipment. Its , , , and composition ensures stability in both reducing and oxidizing conditions, with addition for resistance, compliant with ASTM B425 for rods and B424 for sheets. Key uses encompass acid production vessels, pollution control , and recovery systems in oil and gas operations. Incoloy 020 (UNS N08020) and 028 (UNS N08028) are specialized for and environments, targeting pulp and as well as fertilizer industries. Alloy 020 excels in phosphoric and settings, used in mixing tanks, heat exchangers, and process per ASTM B462 for forgings and B463 for plates, while 028 offers broader resistance to oxidizing and reducing media for similar chemical processing equipment. Incoloy 25-6HN (UNS N08367) is a super-austenitic grade with 6% and additions for superior pitting and resistance in and chemical environments, suitable for heat exchangers and in offshore and chemical processing per ASTM B462. Incoloy 330 (UNS N08330) and DS (W. Nr. 1.4862) prioritize thermal stability for furnace components and heat exchangers. Alloy 330 delivers oxidation resistance up to 1095°C in heat-treating furnaces and chemical process equipment, whereas DS, originally for conveyor belts, resists carburization in heat-treatment applications like retorts and trays. Incoloy 27-7MO (UNS S31277) is a super-austenitic grade with 7% for exceptional resistance to localized in and acidic media, used in plants and chemical processing equipment per ASTM B690. Advanced variants include Incoloy 907 (UNS N19907) and 908 (UNS N09908) for low in turbine components and space applications, and 909 (UNS N19909) with similar properties for precision instruments and cryogenic seals requiring dimensional stability. Incoloy 925 (UNS N09925) provides age-hardenable high strength for oilfield tubing and valves, and 945 (UNS N09945) with 945X (UNS N09946) for ultra-high strength in sour oil and gas service. Additionally, MA956 employs oxide dispersion strengthening for superior oxidation resistance in space reactor components and high-temperature exhaust systems. These represent the progression to specialized, high-performance alloys beyond basic resistance.

Chemical Compositions and Designations

Incoloy alloys are a family of -iron- superalloys with tailored elemental compositions that provide enhanced resistance in harsh environments, such as those involving acids and high temperatures. The specific percentages of , , iron, and alloying elements like , , and are precisely controlled to meet industry standards, ensuring consistent performance across applications. One of the foundational variants, Incoloy 800 (UNS N08800), features a composition dominated by iron with significant and content for balanced oxidation and aqueous resistance. Its limiting chemical composition is as follows:
ElementPercentage Range
(Ni)30.0–35.0
(Cr)19.0–23.0
Iron (Fe)≥39.5
Carbon (C)≤0.10
(Mn)≤1.50
(S)≤0.015
(Si)≤1.0
(Cu)≤0.75
Aluminum (Al)0.15–0.60
(Ti)0.15–0.60
This alloy conforms to ASTM specifications such as B408 for bars, rods, and wire, and B163 for seamless tubes. Incoloy 825 (UNS N08825) incorporates and to bolster resistance to pitting and in reducing acids. Key compositional limits include:
ElementPercentage Range
(Ni)38.0–46.0
(Cr)19.5–23.5
Iron (Fe)≥22.0
(Mo)2.5–3.5
(Cu)1.5–3.0
(Ti)0.6–1.2
Carbon (C)≤0.05
(Mn)≤1.0
(S)≤0.03
(Si)≤0.5
Aluminum (Al)≤0.2
It is standardized under ASTM B425 for rods, bars, and wire, among others. Incoloy 020 (UNS N08020), designed for handling, emphasizes and additions alongside controlled for stabilization. Its composition is:
ElementPercentage Range
(Ni)32.0–38.0
(Cr)19.0–21.0
Iron (Fe)Balance
(Cu)3.0–4.0
(Mo)2.0–3.0
+ (Nb + Ta)8 × C min – 1.00
Carbon (C)≤0.07
(Mn)≤2.0
(P)≤0.045
(S)≤0.035
(Si)≤1.0
Relevant ASTM standards include B729 for pipe and tube. Incoloy 028 (UNS N08028) offers heightened and for superior resistance to oxidizing and reducing media, with aiding in localized prevention. The elemental breakdown is:
ElementPercentage Range
(Ni)30.0–34.0
(Cr)26.0–28.0
Iron (Fe)Balance
()3.0–4.0
()0.6–1.4
Carbon (C)≤0.030
()≤2.50
(P)≤0.030
(S)≤0.030
(Si)≤1.00
It aligns with ASTM B668 for plate, sheet, and strip. Incoloy 330 (UNS N08330) prioritizes alongside and to enhance high-temperature oxidation resistance. Composition details are:
ElementPercentage Range
(Ni)34.0–37.0
(Cr)17.0–20.0
Iron (Fe)Balance
(Si)0.75–1.50
Carbon (C)≤0.08
(Mn)≤2.0
(P)≤0.030
(S)≤0.030
ASTM B511 covers bars, rods, and shapes for this alloy. Specialized variants like Incoloy 800H (UNS N08810) and 800HT (UNS N08811) modify the base 800 composition with tighter controls on carbon (0.05–0.10% for 800H, 0.06–0.10% for 800HT), aluminum + (0.30–1.20% for 800H, 0.85–1.20% for 800HT), and (ASTM 5 or coarser) to optimize creep strength at elevated temperatures. The H and HT suffixes denote these controlled-carbon and aluminum- variants for improved . Other notable variants include Incoloy 907 (UNS N19907), with Ni 35.0–40.0%, Co 12.0–16.0%, Fe balance, Nb 4.3–5.2%, Ti 1.3–1.8%, Al ≤0.2%, and Si 0.07–0.35%, tailored for low and high strength. Incoloy 945 (UNS N09945) features Ni 45.0–55.0%, Cr 19.5–23.0%, Fe balance, Mo 3.0–4.0%, Nb 2.5–4.5%, Cu 1.5–3.0%, Ti 0.5–2.5%, and Al 0.01–0.7%, emphasizing age-hardenability and corrosion resistance. These compositions correlate with UNS designations under the ASTM E527 , ensuring traceability and compliance across global standards.

Applications

Industrial and Chemical Uses

Incoloy alloys, renowned for their superior corrosion resistance in aggressive chemical environments, play a critical role in chemical processing applications. Incoloy 825, a nickel-iron-chromium alloy with additions of molybdenum and copper, is extensively used for piping, reaction vessels, and pumps handling sulfuric and phosphoric acids, particularly in concentrations up to 40% at elevated temperatures. This alloy's resistance to both oxidizing and reducing conditions makes it ideal for fertilizer production facilities, where it withstands the corrosive effects of sulfuric acid in wet-process phosphoric acid manufacturing, ensuring long-term integrity of equipment exposed to acidic slurries and vapors. In the oil and gas sector, Incoloy alloys such as 825 and 925 are employed in tubing, valves, and downhole components for sour service environments containing (H₂S). These materials comply with NACE MR0175/ISO 15156 standards, which specify requirements for metallic materials in H₂S-containing production systems to prevent sulfide stress cracking and , thereby enhancing safety and reliability in offshore and onshore extraction operations. In the , Incoloy 020 and 028 variants provide essential resistance in digesters and bleach towers, where they resist pitting and during the alkaline and chlorine-based bleaching processes, supporting efficient pulp digestion and chemical recovery. For marine and desalination applications, Incoloy 825 and 926 are favored for tubes due to their robust performance against , including resistance to pitting and in chloride-rich brines. These alloys enable reliable operation in multi-stage flash distillation and systems, where tubes must endure high-velocity flows and without degradation. In power generation, Incoloy 800 serves as a primary material for tubing in both and nuclear plants, offering stability in high-pressure, high-temperature environments while mitigating from impurities like chlorides and sulfates. As of 2025, chemical accounts for a significant portion of applications, with nickel-based variants like Incoloy used in this sector due to their corrosion-resistant properties that extend equipment life and reduce maintenance costs in harsh industrial settings.

High-Temperature and Aerospace Applications

Incoloy alloys, particularly variants like 907 and 908, are employed in for components requiring low and high strength at elevated temperatures, such as gas turbine seals, shafts, casings, turbine blades, exhaust systems, and parts. These properties enable precise tolerances in engines, enhancing and resistance to thermal fatigue, with alloy 907 maintaining a low coefficient of of 7.2–8.1 × 10⁻⁶/°C up to 430°C. Alloy 908 supports high-strength cryogenic applications in structures, contributing to lightweight designs in extreme environments. In nuclear and applications, Incoloy 800H serves as a for steam generators and vessels in sodium-cooled fast breeder reactors, leveraging its resistance to high-temperature oxidation and in liquid metal coolants. Additionally, oxide dispersion strengthened (ODS) variant MA956 is utilized in space systems, such as ducting for closed-loop power conversion with inert He-Xe gas, where it provides superior creep resistance at temperatures up to 927°C. This alloy's Y₂O₃-Al₂O₃ dispersion strengthening ensures structural integrity under prolonged exposure, with demonstrated creep life exceeding 5000 hours at 927°C and 14 MPa stress. For furnaces, Incoloy 330 and DS variants are used in muffles, retorts, conveyor belts, baskets, and fixtures due to their oxidation resistance in furnace atmospheres up to 1093°C continuously. In gas turbine environments, Incoloy 800HT is applied in transition ducts and liners, where it withstands high-temperature oxidation and thermal gradients in hot gas paths, as seen in GE LM2500 components. Emerging applications as of 2025 include Incoloy 800H/HT in via reforming, where it forms catalyst tubing, convection sections, and manifolds exposed to high-temperature reducing gases. A notable involves NASA's evaluation of Incoloy MA956 for reactor components, demonstrating exceptional oxidation resistance and mechanical stability at over 1100°C in air, supporting advanced nuclear thermal propulsion systems through enhanced creep and fatigue performance.

Fabrication and Processing

Production Techniques

Incoloy alloys are primarily produced through high-purity melting processes to ensure low levels of impurities, which is critical for their performance. The standard melting technique involves (VIM) or (EAF) melting followed by argon oxygen (AOD) refining to achieve precise control over carbon and gas content. For example, Incoloy alloy 800 has a range of 2475–2525°F (1357–1385°C), allowing for the incorporation of , iron, and in controlled proportions. Following melting, the alloys undergo forming operations to produce semi-finished products such as sheets, tubes, bars, and . Hot forming is typically performed in the temperature range of 1600–2200°F (870–1200°C), with heavy starting at 1850–2200°F (1010–1200°C) and light working down to 1600°F (870°C); temperatures between 1200–1600°F (650–870°C) are avoided to prevent strain-age cracking. Sheets and strips are produced via hot or cold rolling, tubes through or piercing, and bars via , often followed by solution annealing at 1800–1900°F (980–1040°C) for standard Incoloy 800 or 2100–2200°F (1150–1200°C) for Incoloy 800H/800HT to achieve optimal structure and creep resistance. Cold forming is possible but requires intermediate annealing due to the alloy's work-hardening behavior, which is less severe than that of Type 304 . Certain Incoloy variants, such as MA956, employ techniques for enhanced high-temperature properties through oxide dispersion strengthening (ODS). This involves mechanical alloying, a high-energy ball milling process that blends iron-chromium-aluminum powders with particles, followed by , hot , and to consolidate the material into a fine-grained structure stable up to 2700°F (1482°C). This method contrasts with conventional melting by enabling uniform dispersion of submicron particles without melting the base alloy. Quality control in Incoloy production includes rigorous non-destructive testing (NDT) to detect internal defects. per ASTM E213 is standard for bars, pipes, and forgings to identify longitudinal discontinuities, while is used for tubes and wires to ensure surface and near-surface integrity. These methods comply with specifications like ASTM B408 for wrought forms, ensuring material reliability for demanding applications. serves as the primary producer and trademark holder for Incoloy alloys, with global manufacturing facilities focused on high-performance -based materials. Production costs for Incoloy are higher than those for stainless steels due to elevated content and specialized refining processes, but generally lower than for alloys owing to Incoloy's higher iron proportion and simpler compositions.

Welding and Heat Treatment

Incoloy alloys exhibit good weldability using conventional processes such as (GTAW, also known as TIG) and (SMAW). GTAW is preferred for its precision and control, particularly in thin sections, while SMAW suits thicker components or field repairs. Filler metals like ERNiCr-3 (equivalent to Filler Metal 82) are commonly used to match the composition, providing high strength and resistance in welds for alloys such as Incoloy 800 and 825. Preheat is generally not required, though warming the base metal to is recommended if ambient conditions are below 5°C to remove and prevent moisture-related issues. Welding procedures adhere to standards like AWS A5.14 for filler metals and ASME Section IX for qualification, ensuring compliance in structural applications. Post-weld (PWHT) is often unnecessary for corrosion-resistant service but may be applied for stress relief in high-temperature uses. Solution annealing is performed at 980–1120°C (1800–2050°F), followed by rapid water to restore and prevent . For variants like Incoloy 800H and 800HT, age hardening at approximately 700°C (1290°F) for 1–24 hours enhances creep strength by promoting controlled of carbides and phases. Specifications such as AMS 5871 outline requirements for sheet and plate forms post-treatment to maintain material integrity. Key challenges in Incoloy include avoiding , where exposure to 540–760°C (1000–1400°F) during cooling leads to precipitation and . Rapid cooling through this range minimizes risks, and a stabilizing anneal may be used post- for heavy sections in environments. PWHT is selectively applied to balance residual stresses without compromising resistance. is moderate, rated around 50% relative to free-machining steels, requiring tools, low cutting speeds (typically 30–60 m/min), and rigid setups to manage and .

References

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  20. https://www.langleyalloys.com/pitting-resistance-equivalent-number-30/
  21. https://www.specialmetals.com/documents/technical-bulletins/incoloy/incoloy-27-7mo.pdf
  22. https://www.hpalloy.com/Htmlpages/INCOLOY_alloy_27-7MO.html
  23. https://www.researchgate.net/publication/272216603_Oxidation_of_Heat-Resistant_Fe-Base_Incoloy_800_Alloy
  24. https://www.huaxiao-alloy.com/incoloy/
  25. https://www.specialmetals.com/documents/technical-bulletins/incoloy/incoloy-alloy-020.pdf
  26. https://www.specialmetals.com/documents/technical-bulletins/incoloy/incoloy-alloy-25-6hn.pdf
  27. https://www.specialmetals.com/documents/special-metals-quick-reference-guide.pdf
  28. https://www.specialmetals.com/documents/technical-bulletins/incoloy/incoloy-alloy-ds.pdf
  29. https://www.specialmetals.com/documents/technical-bulletins/incoloy/incoloy-alloy-907.pdf
  30. https://www.specialmetals.com/documents/technical-bulletins/incoloy/incoloy-alloy-909.pdf
  31. https://www.specialmetals.com/documents/technical-bulletins/incoloy/incoloy-alloy-925.pdf
  32. http://specialmetals.ir/images/technical_info/Fer-base/Incoloy-alloy-330.pdf
  33. https://www.americanspecialmetals.com/incoloyalloy945-945x.html
  34. https://www.unifiedalloys.com/resources/tech-data/uns-reference
  35. https://seathertechnology.com/incoloy-825-925-material-selection-for-sour-gas/
  36. https://nickelinstitute.org/media/1702/highperformancestainlesssteels_11021_.pdf
  37. https://www.tsmnialloy.com/knowledge/top-applications-of-incoloy-825-in-marine-engineering
  38. https://www.mordorintelligence.com/industry-reports/superalloys-market
  39. http://jw.antonmetal.com/news/the-advantages-of-using-incoloy-907-in-aerospace-applications/
  40. https://www.azom.com/article.aspx?ArticleID=9505
  41. https://link.springer.com/chapter/10.1007/978-1-4684-8366-6_50
  42. https://ntrs.nasa.gov/api/citations/20060008940/downloads/20060008940.pdf
  43. https://www.aeether.com/AEETHER/grades/330.html
  44. https://www.obtturbine.com/incoloy-800ht-turbine-transition-duct-single-combustion-chamber-exit-transition-section-for-ge-lm2500-gas-turbine-parts
  45. https://super-metals.com/melting-procedures-for-production-of-superalloys/
  46. http://specialmetals.ir/images/technical_info/Fer-base/Incoloy-alloy-MA956.pdf
  47. https://www.ncalloys.com/blog/inconel-metal-price/
  48. https://www.huaxiaometal.com/blogs/incoloy-vs-inconel-alloy.html
  49. https://www.specialmetals.com/assets/local/documents/smw/joining.pdf
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