Introduction: Inconel 625 and Inconel 718 are both high-temperature alloys with excellent comprehensive properties. The main difference between them is that Inconel 625 focuses more on corrosion resistance, while Inconel 718 focuses more on high strength. This article will compare these two alloys from various aspects to get a clearer understanding of them.
Basic Information:
Inconel 625:
- Name: Inconel 625
- UNS number: N06625
- W.Nr.: 2.4856
- Brand: INCONEL®
- Substrate: nickel, chromium, molybdenum, niobium
- Type: solid solution strengthened alloy
- Density: 8.44 g/cm³
-Using temperature: high temperature
Inconel Alloy 718:
- Name: Inconel 718
- UNS number: N07718
- W.Nr.: 2.4668
- Brand: INCONEL®
- Substrate: nickel, chromium, iron, niobium
- Type: Precipitation strengthened alloy
- Density: 8.19 g/cm³
-Using temperature: high temperature
introduce:
Inconel 625 is a nickel-chromium alloy that offers high strength, good workability (including welding) and excellent corrosion resistance. Its operating temperature range ranges from cryogenic temperatures to 1800°F (982°C).
Inconel 718 is a high-strength, corrosion-resistant nickel-chromium material that can be used in temperatures ranging from -423°F to 1300°F. This age-hardenable alloy can be easily machined into complex parts. Its welding characteristics, especially its resistance to post-weld cracking, are excellent.
chemical composition:
- The chemical composition analysis of Inconel 625 and Inconel 718 shows that the purity of Inconel 718 is higher than that of Inconel 625, which also makes Inconel 718 more advantageous in terms of strength.
Corrosion performance:
- Inconel 625 has a much lower iron content than Inconel 718, which makes it higher in nickel, chromium and molybdenum.
- Nickel itself has good corrosion resistance, while chromium is the most important corrosion-resistant element in superalloys. Therefore, alloy 625 has better corrosion resistance than alloy 718.
- Molybdenum element can well supplement the alloy’s anti-reduction ability and improve the alloy’s overall corrosion resistance. This further widens the corrosion resistance gap between alloy 625 and alloy 718.
Mechanical behavior:
- Inconel 625 is a solid solution strengthened alloy that is primarily strengthened by solid solution strengthening. Most of the aluminum and titanium in the alloy will dissolve into the alloy matrix (γ-austenite), which has limited strength enhancement effect on the alloy.
- In contrast, Inconel 718 is a precipitation-strengthened alloy. During the production process, aluminum and titanium will precipitate from the matrix to form the γ’ phase, thereby greatly improving the strength of the alloy.
- Niobium and tantalum play a solid solution strengthening role in Inconel 625. Since the atomic radii of niobium and tantalum are very large, their solid solution strengthening effect on 625 alloy is greater than that of aluminum and titanium.
- Niobium and tantalum also play a precipitation strengthening role in Inconel 718. But unlike aluminum and titanium, part of niobium and tantalum enters the γ matrix for solid solution strengthening, and part enters the γ’ phase to increase the precipitation strengthening effect, while more niobium and tantalum can form the γ” precipitation strengthening phase. The strengthening effect of this precipitation strengthening phase at medium and low temperatures is even more obvious than that of the γ’ phase. However, at high temperatures, the effect of the γ” phase will be significantly weakened.
Mechanical performance comparison:
- The following table is a comparison of the mechanical properties of Inconel 625 and Inconel 718, and you can clearly see the gap between them.
| Mechanical properties | Inconel 625 | Inconel 718 |
|———-|————-|————-|
| Tensile strength | 690 MPa | 1275 MPa |
| Yield strength | 276 MPa | 1034 MPa |
Physical properties:
- The following table compares the physical properties of Inconel 625 and Inconel 718.
| Physical Properties | Inconel 625 | Inconel 718 |
|———-|————-|————-|
| Density | 8.44 g/cm³ | 8.19 g/cm³ |
| Melting point range | 2350-2460°F | 2300-2437°F |
| Melting point range | 1290-1350°C | 1260-1336°C |
| Penetration rate | 1.0006 | 1.0006 |
| Curie Temperature | <-320°F | -170°F |
| Curie temperature | -196°C | -112°C |
Heat treatment:
- Inconel 625 is a solid solution strengthened alloy, so its standard heat treatment method is solution treatment. The alloy after solution treatment can achieve optimal performance.
- Inconel 718 is a precipitation-strengthened alloy, so it is usually aged after solution treatment. The purpose is to fully analyze the precipitation strengthening phase and optimize the strength of the alloy.
- Inconel 718 has two heat treatment methods:
– Solution annealed at 1700-1850°F, then rapidly cooled, usually with water, and age hardened at 1325°F for 8 hours, furnace cooled to 1150°F, held at 1150°F for a total aging time of 18 hours and then cool naturally.
– Solution annealed at 1900-1950°F, then rapidly cooled, usually with water, and age hardened at 1400°F for 10 hours, furnace cooled to 1200°F, maintained at 1200°F for a total aging time of 20 hours and then cool naturally.
- The alloy properties obtained by the two heat treatment methods are different and can be selected according to the actual application. The default heat treatment method is the first one.
application:
- Applications for Inconel 625 include aerospace, chemical processing, marine, oil and gas processing, pollution and waste management, power generation and welding products.
- Applications for Inconel 718 include aerospace, automotive, marine, oil and gas processing, power generation and welding products.
Supported products:
- Products supported by Inconel 625 and Inconel 718 include seamless pipes, welded pipes, capillary pipes, coil pipes, thick-walled pipes, elbows, flanges, reducers, tees, pipe caps, round bars, flat steel, square bars, and hexagons Rods, plates, plates, coils, strips, wires, wire rods, filler metals and welding electrodes, etc.
Main criteria:
- The main standards of Inconel 625 include seamless pipes and pipes: ASTM B444, ASTM B829; welded pipes: ASTM B705, ASTM B775; welded pipes: ASTM B704, ASTM B751; welded accessories: ASTM B366; bars: ASTM B446; forgings : ASTM B564; Plate, sheet, and strip: ASTM B443.
- The main standards of Inconel 718 include seamless pipe: SAE AMS 5589, SAE AMS 5590; rods and forgings: ASTM B637, SAE AMS 5662, SAE AMS 5663, SAE AMS 5664; round rods and wire: SAE AMS 5962; welding wire : SAE AMS 5832; Plate, sheet and strip: ASTM B670, ASTM B906, SAE AMS 5596, SAE AMS 5597, SAE AMS 5950.
in conclusion:
Inconel 625 is a solid solution strengthened alloy, its biggest feature is excellent corrosion resistance.
Inconel 718 is a precipitation-strengthened alloy whose biggest feature is very high strength.
Both alloys have their own uses and cannot be substituted for each other.
Tianjin Anton Metal Manufacture Co., Ltd. is a company specializing in the production of various nickel-based alloys, Hastelloy alloys and high-temperature alloy materials. The company was established in 1989 with a registered capital of 10.0 million, specializing in the production and sales of alloy materials. Anton Metal’s products are widely used in aerospace, chemical industry, electric power, automobile, nuclear energy and other fields, and can also provide customized alloy material solutions according to customer needs. If you need to know the price consultation of alloy materials or provide customized alloy material solutions, please feel free to contact the sales staff.
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Post time: Dec-19-2023
