Alloy 617 / Inconel® 617 / 2.4663 / UNS N06617 / Haynes® 617 – nickel alloy NiCr23Co12Mo
Alloy 617 (UNS N06617, 2.4663, NiCr23Co12Mo, Inconel ® 617, Haynes ® 617, VDM ® Alloy 617, Nicrofer ® 5520 Co, NiCr22Co12Mo9) is a high-temperature and high-temperature nickel-based alloy typically containing approximately 22% chromium, 12% cobalt, 9% molybdenum, and approximately 1% aluminum. It combines very good oxidation and carburization resistance with high creep strength. It is primarily used in gas turbines, high-temperature installations, and process equipment.
Materials available at Alfa-Tech – Alloy 617 / Inconel 617 / 2.4663 / UNS N06617
Alloy 617 / Inconel 617 / 2.4663 / UNS N06617 bars – round, hexagonal, rolled / peeled / drawn
Alloy 617 / Inconel 617 / 2.4663 / NiCr23Co12Mo flat bars
Forged bars Alloy 617 / Inconel 617 / 2.4663 / UNS N06617
Alloy 617 / Inconel 617 / 2.4663 Forgings – Cubes, Shafts and Open-die Forgings
Alloy 617 / Inconel 617 / 2.4663 Tubes – Seamless / Welded, as per specification
Alloy 617 / Inconel 617 / 2.4663 sheets, plates, hot- and cold-rolled sheets
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Alloy 617 – chemical composition according to UNS N06617, EN 2.4663, BS NA50, ISO NW6617 and manufacturer's names
The table below distinguishes between the chemical composition limits of the general UNS/ASTM specification, the ranges given for European 2.4663 and the nominal analysis of the commercial HAYNES 617. Different limits do not necessarily indicate a different alloy: the specific product standard and specification edition should be checked.
| Chemical composition | |||||||||||
| Alloy grade | Norma | Ni | Cr | Co | Mo | Al | C | Fe | Mn | Si | Other |
| Alloy 617 / UNS N06617 | ASTM / ASME / UNS | min. two | 20,0–24,0 | 10,0–15,0 | 8,0–10,0 | 0,8–1,5 | 0,05–0,15 | max. 3,0 | max. 1,0 | max. 1,0 | Ti max 0,6; Cu max 0,5; B max 0,006; S max 0,015; P |
| 2.4663 / NiCr23Co12Mo | EN 10302 / EN 10088-1 | rest | 20,0–23,0 | 11,0–14,0 | 8,5–10,0 | 0,7–1,4 | 0,05–0,10 | max. 2,0 | max. 0,2 | max. 0,2 | Ti 0,2-0,6; Cu max 0,5; B max 0,006; S max 0,01; P max. 0,01 |
| NA50 | BS | rest | 20,0–24,0 | 10,0–15,0 | 8,0–10,0 | 0,8–1,5 | 0,05–0,15 | max. 3,0 | max. 1,0 | max. 1,0 | Ti max 0,6; Cu max 0,5; B —; S max 0,015; P max. 0,03 |
| NW6617 / NiCr22Co12Mo9 | ISO 9722 | rest | 20,0–24,0 | 10,0–15,0 | 8,0–10,0 | 0,8–1,5 | 0,05–0,15 | max. 3,0 | max. 2,0 | max. 1,0 | Ti max 0,6; Cu max. 0,5; B/P/S according to ISO edition |
| INCONEL® alloy 617 | Special Metals | min. two | 20,0–24,0 | 10,0–15,0 | 8,0–10,0 | 0,8–1,5 | 0,05–0,15 | max. 3,0 | max. 1,0 | max. 1,0 | Ti max 0,6; Cu max 0,5; B max 0,006; S max 0,015; P |
| HAYNES® 617 | Haynes International – nominal | rest | 22,0 | 12,5 | 9,0 | 1,2 | 0,07 | approx. 1,0 | max. 0,2 | max. 0,2 | Ti approx. 0,3; Cu —; B max. 0,006; S -; P |
The Role of Alloying Elements in Alloy 617
- Nickel (Ni) – creates a stable austenitic matrix and is responsible for good chemical resistance and ductility.
- Chromium (Cr) – supports the production of a protective oxide layer in hot atmospheres.
- Cobalt (Co) i molybdenum (Mo) – strengthen the matrix in solution, improving strength and creep resistance.
- Aluminum (Al) – together with chromium, it helps maintain a resistant protective layer; under unfavorable conditions it can also form internal oxides or nitrides.
- Carbon (C) – takes part in the formation of carbides and changes in structure during long-term operation.
Alloy 617 – characteristics, structure and applications
Alloy 617 is a nickel alloy with a face-centered cubic (FCC) structure, intended for components exposed to high temperatures, stresses, and hot process gases. Compared to alloys designed primarily for corrosive liquids, its main advantage is its combination of heat resistance and long-term strength . VDM documentation emphasizes excellent properties up to approximately 1100°C, but this does not imply unlimited load-bearing capacity at this temperature. The alloy is primarily solution-strengthened and not used as a typical precipitation-hardened alloy by age. However, prolonged exposure in the range of approximately 650–760°C can promote the precipitation of carbides and phases, which alter the material's properties. Therefore, creep resistance, microstructural stability, and impact strength are assessed jointly.
Typical Applications for Alloy 617
- Gas turbines: combustion chambers, covers, hot gas ducts, channels and transition elements.
- Industrial furnaces: muffles, retorts, furnace accessories, radiant tubes, heat treatment baskets.
- Petrochemistry: furnace pipes, pigtails, heaters, reforming installations and high-temperature components.
- Chemical industry: including catalytic grid supports for nitric acid production and process equipment.
- Power engineering: heat exchangers, components of installations working with hot gases and some applications in high-temperature reactor technologies.
- Thin-walled structures: where strength at elevated temperatures and limited component weight are advantageous.
Alloy 617 – physical properties
| Basic Physical Properties of Alloy 617 | |
| Parameter | Typical value |
| Density | 8,36 g / cm³ |
| Melting point (range) | 1332-1380 ° C |
| Thermal conductivity at 20°C | 13,4 W/(m K) |
| Specific heat at 20°C | 419 J/(kg K) |
| Electrical resistivity at 20°C | 1,222 µΩ m |
| Modulus of elasticity E at 25°C | 211 GPa |
| Kirchhoff's modulus G at 25°C | 81 GPa |
| Poisson's ratio ν at 25°C | 0,30 |
| How to interpret the table: The values provided describe typical properties of Alloy 617 at room temperature and are not guaranteed requirements for every product form. The density of 8,36 g/cm³ is used, among other things, for mass calculations, while thermal conductivity and modulus of elasticity vary with temperature. The melting range of 1332–1380°C is not an acceptable operating temperature for the component; load, creep, atmosphere, and service life also determine its selection. | |
In engineering practice, the dependence of properties on temperature is crucial. Thermal conductivity and coefficient of expansion increase with heating, while the modulus of elasticity decreases. The following values are from the Special Metals data sheet for standard Alloy 617.
Thermal and Electrical Properties of Alloy 617 as a Function of Temperature
| Alloy 617 – Thermal and Electrical Properties as a Function of Temperature | ||||
| Temperature [° C] | Specific heat cp [J/(kg K)] | Conductivity λ [W/(m K)] | Resistivity ρ [µΩ m] | Expansion α [10−6/K] |
| 20 | 419 | 13,4 | 1,222 | |
| 100 | 440 | 14,7 | 1,245 | 11,6 |
| 200 | 465 | 16,3 | 1,258 | 12,6 |
| 300 | 490 | 17,7 | 1,268 | 13,1 |
| 400 | 515 | 19,3 | 1,278 | 13,6 |
| 500 | 536 | 20,9 | 1,290 | 13,9 |
| 600 | 561 | 22,5 | 1,308 | 14,0 |
| 700 | 586 | 23,9 | 1,332 | 14,8 |
| 800 | 611 | 25,5 | 1,342 | 15,4 |
| 900 | 636 | 27,1 | 1,338 | 15,8 |
| 1000 | 662 | 28,7 | 1,378 | 16,3 |
| How to interpret the table: In the range of 20–1000°C, the specific heat increases in this comparison from 419 to 662 J/(kg K), and thermal conductivity from 13,4 to 28,7 W/(m K). The linear expansion coefficient α is an average value for the range from the reference temperature (approximately 26°C) to the temperature indicated in the table, not an instantaneous value. When designing pipes, casings, and heat exchangers, both heat transfer and thermal expansion should be considered. The "—" sign at 20°C indicates no interval value, not zero expansion. | ||||
α is the average coefficient of linear expansion from approximately 26°C to the indicated temperature, not the instantaneous coefficient at a single point. Special Metals considers thermal conductivity and specific heat to be calculated values. These data are approximate for analysis purposes, not guaranteed acceptance parameters.
Elastic moduli and Poisson's ratio at high temperature
| Alloy 617 – Elastic Parameters as a Function of Temperature | |||
| Temperature [° C] | E modulus [GPa] | G-modulus [GPa] | Poisson's number ν |
| 25 | 211 | 81 | 0,30 |
| 100 | 206 | 80 | 0,30 |
| 200 | 201 | 77 | 0,30 |
| 300 | 194 | 75 | 0,30 |
| 400 | 188 | 72 | 0,30 |
| 500 | 181 | 70 | 0,30 |
| 600 | 173 | 66 | 0,30 |
| 700 | 166 | 64 | 0,30 |
| 800 | 157 | 61 | 0,30 |
| 900 | 149 | 57 | 0,30 |
| 1000 | 139 | 53 | 0,31 |
| 1100 | 129 | 49 | 0,32 |
| How to interpret the table: As temperature increases, the elastic stiffness of Alloy 617 decreases significantly: Young's modulus E drops from 211 GPa at 25°C to 129 GPa at 1100°C, and the Kirchhoff modulus G from 81 to 49 GPa. The Poisson's ratio remains within the presented range, close to 0,30–0,32. When calculating deflections, thermal stresses, and strain compensation, do not substitute only room-temperature modulus values into the high-temperature model. | |||
In thermal resistance calculations, the E modulus from room temperature should not be substituted for elements operating at 800–1000°C: the difference is significant, especially with cyclical temperature changes.
Alloy 617 – Mechanical Properties at Room Temperature
The following are representative values obtained from tests on saturated products; they should not be considered the minimum requirements of any standard. Yield strength is Rp0,2, Rm is tensile strength, A is elongation, and HB is Brinell hardness.
| Alloy 617 – mechanical properties of supersaturated products | ||||
| Appearance and condition of the product | Rp0,2 [MPa] | Rm [MPa] | A [%] | Hardness [HB] |
| Hot-rolled plates, solution heat treated | 322 | 734 | 62 | 172 |
| Hot-rolled bars, solution heat treated | 318 | 769 | 56 | 181 |
| Cold drawn, solution heat treated tubes | 383 | 758 | 56 | 193 |
| Cold-rolled sheets/stripes, solution heat treated | 351 | 755 | 58 | 173 |
| How to interpret the table: The values refer to sample products in the solution heat-treated condition; they do not automatically constitute minimum delivery requirements. In this group of results, Rm is 734–769 MPa, yield strength Rp0,2 is 318–383 MPa, elongation is 56–62%, and hardness is 172–193 HB. Variations between plates, bars, pipes, and sheets result from, among other things, differences in manufacturing technology and processing history. Acceptance requirements should always be based on the standard appropriate for the ordered material form and condition. | ||||
Source: Special Metals, INCONEL alloy 617, Table 5. Sheet, strip, and plate tests were performed in the transverse direction. Minimum values for a specific order depend on the product form and standard, e.g., ASTM B166 or ASTM B168.
Creep resistance of Alloy 617 – creep and resistance to long-term loading
Creep refers to the slow, progressive deformation of a material under the action of a constant stress at high temperature. For turbine components, furnace tubes, and heat exchangers, creep parameters are often more important than the short-term strength Rm measured at room temperature. VDM data distinguishes between stresses corresponding to 1% creep strain and stresses that cause rupture after a specified time. The table below presents only the creep rupture strength at 10,000 and 100,000 hours.
| Alloy 617 – Creep Rupture Strength | ||
| Temperature [° C] | Break after 10,000 h – Rm/10⁴h [MPa] | Break after 100,000 h – Rm/10⁵h [MPa] |
| 600 | 260 | 190 |
| 650 | 170 | 125 |
| 700 | 123 | 95 |
| 750 | 90 | 65 |
| 800 | 65 | 43 |
| 850 | 45 | 27 |
| 900 | 30 | 16 |
| 950 | 18 | 8,5 |
| 1000 | 10 | approx. 4,5* |
| How to interpret the table: The table shows the stresses corresponding to the specimens' failure after the indicated time, not the allowable stresses for design. At 900°C, the values drop to 30 MPa at 10,000 h and 16 MPa at 100,000 h, illustrating the importance of high-temperature loading time. The value of approximately 4,5 MPa at 1000°C and 100,000 h is an estimate marked with an asterisk. Selection of the component thickness and load requires appropriate design regulations and consideration of creep and service life. | ||
Source: VDM Metals, 2021 VDM Alloy 617 data sheet, Table 6; *the value for 1000°C / 100,000 h is an estimate. The data describe the statistical behavior of the material under specific test conditions – they are not allowable design stresses . The latter should be obtained from the appropriate, current edition of ASME, VdTÜV or other design specification.
Change in impact strength after long-term exposure to temperature
Prolonged annealing can alter the microstructure of Alloy 617 and reduce the fracture energy of the samples. This relationship is non-monotonic and strongly depends on time and temperature. Selected impact test results from the Special Metals data sheet, performed after sample exposure, are presented below.
| Alloy 617 – impact strength after high temperature exposure | ||
| Exposure temperature [°C] | Time [h] | Impact energy [J] |
| Without exposure | 232 | |
| 595 | 1 000 | 302 |
| 595 | 8 000 | 133 |
| 595 | 12 000 | 94 |
| 650 | 100 | 259 |
| 650 | 1 000 | 47 |
| 650 | 12 000 | 52 |
| 705 | 100 | 77 |
| 705 | 4 000 | 65 |
| 760 | 100 | 76 |
| 760 | 4 000 | 84 |
| 760 | 12 000 | 91 |
| How to interpret the table: Impact energy after thermal exposure does not change linearly with time or temperature. For example, without exposure, 232 J was obtained, after 1000 h at 595°C – 302 J, but after 12,000 h at the same temperature – 94 J. In turn, at 650°C and 1000 h, 47 J was obtained. These results indicate that long-term exposure can significantly alter fracture toughness due to microstructural changes; the test conditions and method must comply with the manufacturer's data sheet. These results should not be applied directly to every product or welded joint. | ||
Data from Special Metals, Table 7. Results refer to a specific test program; without information about the sample geometry and method, these values should not be automatically identified with the guaranteed KV according to EN ISO 148-1. Key conclusion: good creep resistance does not mean constant impact strength after long-term exposure.
Alloy 617 – resistance to oxidation, carburization and nitriding
The high-temperature corrosion resistance of alloy 617 is primarily due to its chromium and aluminum content. Oxide layers form on the surface, restricting further oxygen transport. Scale adhesion is crucial during cyclic heating and cooling; in highly aggressive atmospheres, internal corrosion, nitrogen penetration, and the effects of water vapor must also be considered.
Oxidation and carburization – the difference between resistance and complete insensitivity
- Oxidation: high resistance in many conditions up to about 1100°C, although it can be significantly changed by gas flow rates and thermal cycles.
- Carburizing: The alloy exhibits very good resistance in selected carbon-containing atmospheres. This does not imply resistance to every gas mixture.
- Nitriding (nitration): resistance to nitrogen penetration depends on temperature and nitriding potential; under certain conditions, aluminum nitrides may form beneath the surface.
- Chlorides and chlorine: The material's behavior depends on the concentration, presence of oxygen and water, temperature, and exposure time. An alloy should not be unconditionally called resistant to all chloride environments.
- Sulfur compounds: Hot sulfur atmospheres can also be aggressive towards nickel alloys. Individual assessment is required.
Carburization resistance comparison – 1095°C, 25 hours
The figures below are the mass gain associated with carbon uptake in the Special Metals laboratory test (hydrogen with 2% methane), expressed in g/m². The smaller gain in this particular test indicates limited carbon uptake but does not constitute a universal ranking of materials for every furnace.
| Carburization resistance comparison – 1095°C, 25 hours | |
| Stop | Weight gain [g/m²] |
| Alloy 617 | 10 |
| Alloy 600 | 28 |
| Alloy 625 | 37 |
| Alloy 800 | 53 |
| Alloy X | 71 |
| How to interpret the table: In the presented identical test at 1095°C for 25 hours, Alloy 617 showed a weight gain of 10 g/m², while Alloy 600 showed a weight gain of 28 g/m² and Alloy X showed a weight gain of 71 g/m². While this lower weight gain is beneficial under these specific conditions, it does not, in itself, determine full industrial durability. Atmospheric composition, the presence of soot, exposure time, thermal cycling, and changes in surface layer properties also play a role. | |
Source: Special Metals, INCONEL alloy 617, Table 9, 25 h exposure at 1095°C. Comparison applies only to the specific test environment.
Heat treatment, plastic treatment and machining of Alloy 617
The alloy can be forged, rolled, bent, and cold-formed, but its high strength requires appropriate deformation forces and frequent intermediate annealing. Surface contamination with sulfur, lead, or other low-melting elements can cause damage during heating.
| Alloy 617 – heat and plastic treatment parameters | |
| Process | Indicative parameters / notes |
| Forging / large hot deformations | approx. 1010–1205°C (heavy forging range according to Special Metals) |
| Slight hot deformation | possible up to approx. 925°C; monitor the drop in charge temperature |
| Cold forming | high strain hardening, intermediate annealing recommended |
| Inter-operational annealing | approx. 1040°C; time selection depending on cross-section and degree of compression |
| Solution annealing / solution annealing | typically approx. 1175°C, then rapid cooling with water or air depending on the product |
| Machining | sharp tools, stable mounting, appropriate feed rate limiting the hardening of the surface layer |
| How to interpret the table: The range of 1010–1205°C applies to the indicated forging and large hot deformations, while approximately 1040°C is given for intermediate annealing, and approximately 1175°C for solution annealing. These temperatures should not be considered a single, interchangeable machining procedure. The selection of soaking time, degree of deformation, and cooling method depends on the cross-section, form of the product, and the required properties. During machining, the effects of rapid strain hardening and tool overheating must be minimized. | |
There is no single, universal heat treatment cycle for bar, sheet, pipe, or large forging. Changing grain size can improve specific creep properties, but it can also affect fatigue strength and formability.
Welding Alloy 617 – Filler Metals and Important Limitations
Alloy 617 is characterized by good weldability using GTAW/TIG, GMAW/MIG, and coated electrode methods, when appropriate filler materials are used. Careful removal of oil, sulfur, marking paints, and other contaminants from the welding zone is essential.
| Alloy 617 – welding consumables | |
| Type of additional material | Mark |
| Welding wire/rod | AWS A5.14: ERNiCrCoMo-1 (e.g. INCONEL Filler Metal 617, VDM FM 617) |
| Coated electrode | AWS A5.11: ENiCrCoMo-1 (e.g. INCONEL Welding Electrode 117) |
| How to interpret the table: ERNiCrCoMo-1, according to AWS A5.14, designates a welding material in the form of a wire or rod, while ENiCrCoMo-1, according to AWS A5.11, refers to a coated electrode. These designations should not be confused with each other, nor should one process be automatically substituted for the other. The appropriate filler material and welding parameters should be determined using the WPS method, taking into account the joint geometry, thermal conditions, corrosion requirements, and long-term weld strength. | |
Important process note: The Haynes data sheet states that preheating or post-weld treatment is not normally required for typical welding, but VDM warns against relaxation cracking under specific service conditions, especially at 550–780°C. The manufacturer recommends post-weld stabilization around 980°C for 3 hours in certain situations. This is not an automatic requirement for all joints: it depends on the design, procedure, and material condition.
Standards and specifications Alloy 617 / 2.4663 / UNS N06617
The UNS number identifies the alloy composition but does not replace the standard that specifies the product form and acceptance requirements. When ordering material, please specify its form, standard, processing condition, dimensional tolerance, and the required quality document.
| Alloy 617 Standards and Specifications | |
| Specification | Product type |
| ASTM B166 / ASME SB-166 | rods and wires |
| ASTM B168 / ASME SB-168 | thick and thin sheets, strips |
| ASTM B167 / ASME SB-167 | seamless pipes |
| ASTM B564 / ASME SB-564 | forgings |
| ASTM B546 / ASME SB-546 | selected welded pipes, in accordance with the scope of the standard |
| DIN 17752 / DIN 17753 | historical DIN standards: rods/wires |
| DIN 17750 / DIN 17751 | historical DIN standards: sheets / pipes |
| EN 10302 | grades of heat-resistant steel and nickel alloys; depending on the issue and scope |
| VdTÜV-Werkstoffblatt 485 | product/performance requirements for specific applications |
| AMS 5887 / 5888 / 5889 | selected rods, forgings, sheets and strips in aviation |
| How to interpret the table: The designations Alloy 617, UNS N06617, or 2.4663 alone do not define all requirements for the finished product. For example, ASTM B166 applies to rods and wires, ASTM B168 to sheet and strip, ASTM B167 to seamless tubes, and ASTM B564 to forgings. Orders must include the standard, its edition, material form, dimensions, heat treatment condition, and required testing. Historical DIN standards, aerospace specifications, and pressure-related specifications should be verified for validity and applicability. | |
Older DIN numbers and product codes are still found in documentation. Before using them in a project, check the current edition of the specification and whether the product and material condition fall within its scope.
Alloy 617 – Trade Names, Designations and Substitutes
| Alloy 617 – Trade Names and Other Designations | |
| Name / designation | Type and notes |
| Alloy 617 / UNS N06617 | general alloy designation and UNS number |
| 2.4663 / NiCr23Co12Mo | EN/DIN marking |
| NiCr22Co12Mo9 | composition designation in the ISO system |
| INCONEL® alloy 617 | trade name Special Metals |
| HAYNES® 617 | trade name Haynes International |
| VDM® Alloy 617 / Nicrofer® 5520 Co | trade name VDM Metals |
| ATI 617™ | ATI trade name |
| BS NA50 | common historical British designation; verify specification |
| Alloy 617 B / 2.4673 | a special type of VDM; do not use without comparing the requirements |
| Nicrofer S 5520 / VDM FM 617 | welding consumable, non-standard base rod name Alloy 617 |
| How to interpret the table: INCONEL alloy 617, HAYNES 617, and VDM Alloy 617 are trade names referring to the UNS N06617 alloy family; however, the product documentation is the deciding factor when purchasing. Alloy 617 B / 2.4673 is a special variety and should not be considered an unconditional replacement for 2.4663. Similarly, Nicrofer S 5520 / VDM FM 617 describes a welding consumable, not a standard base rod grade. Verifying the certificate helps avoid confusion between the alloy, its variety, and the filler metal. | |
Not to be considered direct replacements: N06007 and the NiCr22Fe20Mo6Cu2Nb description refer to a different composition set than Alloy 617. Documentation for 2.4663 must be in accordance with UNS N06617 and the appropriate product standard. Conformity to a specific batch is confirmed by an acceptance certificate.
Frequently Asked Questions – Alloy 617 / Inconel 617
Are Alloy 617 and Inconel 617 the same alloy?
Yes. Alloy 617 is an alloy designated UNS N06617 and European number 2.4663; INCONEL® 617 is a trademark of Special Metals. Other manufacturers offer the material with the corresponding chemistry, such as HAYNES 617 or VDM Alloy 617.
Is Alloy 617 stainless steel?
No. Its matrix is nickel, not iron. It is a nickel superalloy with particularly good high-temperature properties.
What is the hardness of Alloy 617?
In the supersaturated state, sample tests by Special Metals showed hardness values of approximately 172–193 HB, depending on the product form. The guaranteed value is based on the specifications and acceptance certificate.
Up to what temperature can Alloy 617 be used?
VDM documentation describes very good heat resistance up to approximately 1100°C, while typical high-stress applications are often designed for lower temperatures. The operating limit is determined based on service life, creep, atmospheric conditions, and the appropriate design standard.
Is Alloy 617 suitable for use in seawater?
It's not typically the first choice for long-term seawater service. If chloride corrosion in the liquid is the dominant concern, it's worth comparing Alloy 625 with other alloys designed for such environments.
Can Alloy 617 be welded?
Yes. Among other materials, ERNiCrCoMo-1 wire and ENiCrCoMo-1 electrodes are used. For components operating in a temperature range conducive to relaxation cracking, the need for post-weld treatment must be assessed.
Can Alloy 617 be hardened and tempered?
The classic heat treatment typical of quenched and tempered steels is not used. Alloy 617 is essentially a solution-strengthened alloy; solution heat treatment and controlled plastic working are typically used.
How is Alloy 617 different from Alloy 625 and Alloy 600?
Alloy 617 contains significant amounts of cobalt and molybdenum, along with an aluminum alloy, and its strengths include creep strength and oxidation resistance. Alloy 625 is often chosen for highly corrosive aqueous environments, while Alloy 600 is a simpler Ni-Cr-Fe alloy without such significant Co and Mo additions.