Inconel Alloy 625 (UNS designation N06625) is a nickel-based superalloy that possesses high strength properties and resistance to elevated temperatures. It also demonstrates remarkable protection against corrosion and oxidation. Its ability to withstand high stress and a wide range of temperatures, both in and out of water, as well as being able to resist corrosion while being exposed to highly acidic environments makes it a fitting choice for nuclear and marine applications.[1][2][3]
| Inconel 625 | |
|---|---|
 Cladding overlay in a tube with Inconel 625 | |
| Synonym | Werkstoff 2.4856 |
| Material type | Alloy |
| Alloy properties | |
| UNS identifier | N06625 |
| Alloy type | Nickel-based superalloy |
| Composition |
|
| Physical properties | |
| Density (ρ) | 8.4 g/cm3 |
| Mechanical properties | |
| Young's modulus (E) | 207.5-147.5 @ 70–1,600 °F (21–871 °C) (annealed) 204.8-148.2 @ 70–1,600 °F (21–871 °C) (solution treated) |
| Tensile strength (σt) | Rod, bar, plate: 120–160 ksi (827–1,103 MPa) (as rolled), 120–150 ksi (827–1,034 MPa) (annealed) |
| Elongation (ε) at break | Rod, bar, plate: 60-30% (as rolled and annealed) |
| Poisson's ratio (ν) | 0.278-0.336 @ 70–1,600 °F (21–871 °C) (annealed) 0.312-0.289 @ 70–1,600 °F (21–871 °C) (solution treated) |
| Hardness—Brinell | Rod, bar, plate: 175-240 (as rolled) |
| Thermal properties | |
| Melting temperature (Tm) | 2,350–2,460 °F (1,288–1,349 °C) |
| Thermal conductivity (k) | 50 BTU/(hr·ft⋅°F) @ −250 °F (−157 °C) – 175 BTU/(hr·ft⋅°F) @ 1,800 °F (982 °C) |
| Specific heat capacity (c) | 0.096-0.160 BTU/(lb⋅°F) (0.402-0.669 J/g⋅°C) @ 0–2,000 °F (−18–1,093 °C) |
| Electrical properties | |
| Permeability (μ) | 1.006 @ 200 Oe (15.92 kA/m) |
| Values displayed for tensile strength, elongation, and hardness are shown for various products under 4 in (10.2 cm) in size, and are measured at room temperature. | |
Inconel 625 was developed in the 1960s with the purpose of creating a material that could be used for steam-line piping. Some modifications were made to its original composition that have enabled it to be even more creep-resistant and weldable. Because of this, the uses of Inconel 625 have expanded into a wide range of industries such as the chemical processing industry, and for marine and nuclear applications to make pumps and valves and other high pressure equipment.[4][1]
Because of the metal's high Niobium (Nb) levels as well as its exposure to harsh environments and high temperatures, there was concern about the weldability of Inconel 625. Studies were therefore conducted to test the metal's weldability, tensile strength and creep resistance, and Inconel 625 was found to be an ideal choice for welding.[3] Other well known names for Inconel 625 are Haynes 625, Nickelvac 625, Nicrofer 6020, Altemp 625 and Chronic 625
Chemistry
editInconel 625 was designed as a solid solution strengthened material with no significant microstructure. This holds true at low and high temperatures, but there is a region (923 to 1148 K) where precipitates form that are detrimental to the creep properties, and thus the strength, of the alloy. Under any creep conditions (high temperature with an applied stress), M23C6-type carbides form at the grain boundaries. When tested at 973 K, γ” precipitates begin forming. These γ” phase precipitates are ordered A3 B type with a composition of Ni3(Nb, Al, Ti) and a tetragonal crystal structure. They form a disk-shaped morphology and are coherent with respect to the matrix. When tested at 998 K, a δ-phase precipitate begins forming which consist of Ni3(Nb, Mo) in an orthorhombic crystal structure. They form in a needle-like morphology and are incoherent with the matrix. Both of these precipitates can be completely dissolved back into the matrix when the sample is heated to 1148 K for 5 hours. This leads to the ability to recover creep properties of the alloy to prolong the materials lifetime.[5]
ASTM Specifications
editASTM (American Society for Testing and Materials) for various products made out of Inconel 625 are as follow:
| Pipe Seamless | Pipe Welded | Tube Seamless | Tube Welded | Sheet/Plate | Bar | Forging | Fitting | Wire |
|---|---|---|---|---|---|---|---|---|
| B444[6] | B705[7] | B444[6] | B704[8] | B443[9] | B446[10] | – | – | – |
Markets
editMarkets for Inconel 625 include:
- Offshore
- Marine
- Nuclear
- Chemical Processing
- Aerospace
- Glow Plugs
Applications
editProduct and technology applications of Inconel 625 include:[11]
- Seawater components
- Flare stacks
- Aircraft ducting systems
- Fabrication with Inconel 625
- Specialized seawater equipment
- Chemical process equipment
- Turbine shroud rings
- Engine thrust-reverser systems
- Jet engine exhausts systems
- Boiler furnaces
Specifications
editSpecifications and certifications include:[12]
- AMS: 5599, 5666, 5837, 5869
- MS: 5837
- ASME: SB 443 Gr 1, SB 446 Gr 1
- ASTM: B 443 Gr 1, B 446 Gr 1
- EN: 2.4856
- ISO: 15156-3
- NACE: MR0175-3
- UNS: N06625
- Werkstoff: 2.4856
See also
editReferences
edit- ^ a b "Special Metals INCONEL® Alloy 625". ASM Aerospace Specification Metals Inc.
- ^ "High Temp Super Alloys". ASM Aerospace Specification Metals Inc.
- ^ a b Eiselstein, H.L.; Tillack, D.J. (1991). "The Invention and Definition of Alloy 625". Superalloys 718, 625 and Various Derivatives (1991). TMS The Minerals, Metals and Materials Society. pp. 1–14. doi:10.7449/1991/Superalloys_1991_1_14. ISBN 0-87339-173-X.
- ^ Smith, G.D.; Tillack, D.J.; Patel, S.J. (2001). "Alloy 625 – Impressive Past/Significant Presence/Awesome Future". Superalloys 718, 625, 706 and Various Derivatives. TMS The Minerals, Metals and Materials Society. pp. 35–46. doi:10.7449/2001/Superalloys_2001_35_46. ISBN 0-87339-510-7.
- ^ Mathew, M. D. (2008). "Microstructural changes in alloy 625 during high temperature creep". Materials Characterization. 59 (5): 508–513. doi:10.1016/j.matchar.2007.03.007.
- ^ a b "Standard Specification for Nickel-Chromium-Molybdenum-Niobium Alloys and Nickel-Chromium-Molybdenum-Silicon Alloy Pipe and Tube". www.astm.org. doi:10.1520/b0444-23. Retrieved 2024-10-17.
- ^ "Standard Specification for Nickel-Chromium-Molybdenum-Niobium Alloy, Nickel-Chromium-Molybdenum-Silicon Alloy, and Nickel-Iron-Chromium-Molybdenum-Copper Alloy Welded Pipe". www.astm.org. doi:10.1520/b0705-24. Retrieved 2024-10-17.
- ^ "Standard Specification for Welded Nickel Alloy Tubes". www.astm.org. doi:10.1520/b0704-23. Retrieved 2024-10-17.
- ^ "Standard Specification for Nickel-Chromium-Molybdenum-Columbium Alloy and Nickel-Chromium-Molybdenum-Silicon Alloy Plate, Sheet, and Strip". www.astm.org. doi:10.1520/b0443-19. Retrieved 2024-10-17.
- ^ "Standard Specification for Nickel-Chromium-Molybdenum-Niobium Alloy, Nickel-Chromium-Molybdenum-Silicon Alloy, and Nickel-Chromium-Molybdenum-Tungsten Alloy Rod and Bar". www.astm.org. doi:10.1520/b0446-23. Retrieved 2024-10-17.
- ^ Newman, Ian. "5 applications of INCONEL alloys". www.corrotherm.co.uk. Retrieved 2024-11-13.
- ^ "Inconel nickel-chromium alloy 625 (UNS N06625/W.Nr. 2.4856)" (PDF). www.specialmetals.com. August 13, 2013. Retrieved November 17, 2024.