Views: 0 Author: Site Editor Publish Time: 2025-07-14 Origin: Site
Nickel-based alloys are widely used in the aerospace, chemical, ocean engineering and nuclear industries for their excellent performance in high-temperature and high-corrosion environments. Among them, Inconel 625 and Inconel 718 are two representative high-performance alloys. Although they belong to the same Inconel family and both have good oxidation and corrosion resistance, there are significant differences in their composition, mechanical properties, heat treatments, and application scenarios. Understanding the differences between Inconel 625 and 718 (Inconel 625 vs 718) is important for material selection and engineering design. Next, we will analyze the similarities and differences between these two alloys from the aspects of composition, performance comparison and typical applications. Contact us
Inconel 625
Inconel 718
Inconel 625 is also known as Incoloy 625. It is an alloy composed mainly of nickel, chromium and molybdenum with excellent resistance to pitting and corrosion cracking. Alloy 625 has extraordinary mechanical properties at very low and high temperatures. Alloy 625 has high fracture strength and tensile strength with excellent weldability and brazing properties. Alloy 625 has excellent corrosion resistance to inorganic acids such as sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid, etc. The large amount of nickel in the alloy enables it to withstand severe corrosive environments such as neutral salts, alkaline media and seawater.
Inconel 718 is a nickel-based high temperature alloy, mainly composed of nickel, chromium, iron and titanium. It has excellent oxidation resistance and can maintain stable mechanical properties at high temperatures. As a result, it is widely used in the manufacture of components in high temperature environments.
Another characteristic of the alloy is that the alloy organization is particularly sensitive to the thermal processing technology, mastery of the alloy phase precipitation and dissolution laws and organization and process performance of the interrelationship between the different. The use of the same requirements to develop a reasonable, feasible process procedures, you can get to meet the different strength levels and the use of a variety of parts required.
STANDARD | WERKSTOFF NR. | UNS | GOST | AFNOR | JIS | BS | EN | OR |
Inconel 625 | 2.4856 | N06625 | ХН75МБТЮ | NC22DNB4M | NCF 625 | NA 21 | NiCr22Mo9Nb | ЭИ602 |
STANDARD | WERKSTOFF NR. | UNS |
Inconel 718 | 2.4668 | N07718 |
Ni | Fe | C | Mn | Si | Cr2 | Mo | Co | Al | Ti | Nb + Ta | P | S |
58.0 min | 5.0 max | 0.10 max | 0.50 max | 0.50 max | 20.0-23.0 | 8.0-10.0 | 1.0 max | 0.40 max | 0.40 max | 3.15–4.15 | 0.015 max | 0.015 max |
Grade | C | Mn | Si | S | Cu | Fe | Ni | Cr |
Inconel 718 | 0.08 max | 0.35 max | 0.35 max | 0.015 max | 0.30 max | - | 50.00 - 55.00 | 17.00 - 21.00 |
Density | Melting Point | Tensile Strength | Yield Strength (0.2%Offset) | Elongation |
8.4 g/cm3 | 1350 °C (2460 °F) | Psi - 1,35,000 , MPa -930 | Psi - 75,000 , MPa - 517 | 42.50% |
Element | Density | Melting Point | Tensile Strength | Yield Strength (0.2%Offset) | Elongation |
Inconel 718 | 8.2 g/cm3 | 1350 °C (2460 °F) | Psi – 1,35,000 , MPa – 930 | Psi – 75,000 , MPa – 482 | 45% |
Inconel 625:
Due to its high chromium, molybdenum and niobium content, Inconel 625 exhibits excellent corrosion resistance in a wide range of extreme environments, especially in oxidizing and reducing environments. It has excellent corrosion resistance in brine, seawater, acidic media, and high-temperature chloride and sulfate environments. As a result, it is commonly used in the chemical, marine engineering, nuclear, and aerospace industries.
Inconel 718:
Although Inconel 718 is not as corrosion resistant as Inconel 625, it still has good corrosion resistance at high temperatures and high pressures, especially in high-temperature oxidation and creep environments. This makes it an ideal material for aero-engine turbine components, rocket engine parts, and nuclear reactor components.
Inconel 625 has good thermal processing properties and a wide range of thermal processing temperatures, generally between 950 - 1200℃. In the hot working process, attention should be paid to controlling the heating rate and deformation to avoid overheating, overburning and other defects.
Inconel 718 is relatively difficult to hot work due to its high alloying degree. The hot working temperature should be strictly controlled at 950 - 1050 ℃, in this temperature range, the alloy has good plasticity, can effectively avoid the generation of thermal cracks. At the same time, the cooling rate after hot working also has an important influence on the organization and properties of the alloy.
Inconel 625 cold working performance is better, can be stamping, cold molding and other processing operations . However, in the cold working process, with the increase of processing deformation, the material will appear work hardening phenomenon, the need for timely intermediate annealing treatment, in order to restore the plasticity of the material.
Inconel 718 cold working is also prone to work hardening, and because of its high strength, more stringent requirements for processing equipment and molds. Usually need to use a combination of multiple cold working and intermediate annealing process, the intermediate annealing temperature is generally around 850 ℃, in order to reduce the hardness of the material, improve processing performance.
Inconel 625 has excellent weldability and is relatively resistant to post-weld cracking. This makes it easier to work with when fabricating complex structures and reduces the risk of weld defects.
Inconel 718 also has excellent weldability and a high resistance to post-weld (age) cracking, a significant advantage among precipitation-strengthened alloys. However, due to its complex strengthening mechanism, welding parameters and processes need to be tightly controlled during welding to ensure that the mechanical properties of the final part are not compromised. Improper welding can lead to degradation of properties or cracking in the weld area.
Inconel 625 has good and consistent strength right out of the annealed condition. This is an advantage for applications where extreme strength is not required, or where a simplified manufacturing process is desired. However, the strength levels are generally not as good as those of age-hardened Inconel 718.
Inconel 718, when properly age-hardened, can exhibit very high yield, tensile and creep fracture strengths. This is a key reason for its popularity in highly stressed, high-temperature applications such as aerospace and gas turbines. Its strength advantages are particularly strong in specific temperature ranges.
1. Excellent corrosion resistance: excellent performance in a variety of harsh corrosive environments, especially seawater, acidic media and chloride environment.
2. Good high-temperature strength: high mechanical properties and oxidation resistance at elevated temperatures.
3. Excellent fatigue strength and resistance to stress corrosion cracking.
4. No age-hardening required: good strength can be achieved in the annealed condition, simplifying the manufacturing process.
5. Good weldability and formability.
1. Not as strong as age-hardened Inconel 718.
2. Higher cost.
3. More difficult to machine.
1. Very High Strength: Excellent tensile, yield, creep, and fracture strength over a wide temperature range (from cryogenic to 700 ℃) after age-hardening.
2. Excellent fatigue resistance.
3. Good weldability: High resistance to post-weld cracking, which is essential for the manufacture of complex components.
4. Good oxidation resistance at high temperatures.
1. Corrosion resistance may be slightly less than Inconel 625 in some extreme environments.
2. Requires complex age-hardening heat treatments to achieve optimum performance.
3. High cost
4. Difficult to machine and has a tendency to work-harden.
Inconel 625 and Inconel 718 are two important nickel-based superalloys, each with unique performance advantages and application scenarios. Inconel 625 is excellent in corrosion resistance, and is suitable for oil and gas, chemical industry and other areas that require high corrosion resistance; while Inconel 718 has advantages in high temperature strength, fatigue properties and hardness, etc. It is mainly used in aerospace, high-performance automotive engines and other areas that require high mechanical properties. Inconel 718 has advantages in high-temperature strength, fatigue properties and hardness, and is mainly used in aerospace, high-performance automobile engines and other fields with harsh requirements on the mechanical properties of materials. In actual engineering applications, engineers and manufacturers should consider the selection of suitable alloys according to the specific use environment, performance requirements, processing technology and cost and other factors, in order to ensure that the quality and performance of the product is optimized.
