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Inconel 600 vs 601 vs 625: Nickel-based alloy pipe performance comparison and selection guide

Nickel-based alloys, especially Inconel-series alloys, are widely used in aerospace, chemical equipment, petrochemicals, and other fields due to their excellent high temperature resistance, corrosion resistance, and mechanical strength. With the increasing diversification of industrial needs, industrial users need to consider the cost-effectiveness of alloys in addition to their corrosion resistance and high temperature strength when selecting materials. Especially in the face of harsh environments, the accuracy of material selection directly affects the life and safety of equipment. Therefore, it is particularly important to compare and analyze the technical differences of different Inconel alloys to help users make more rational material selection decisions.


This article will thoroughly examine the performance differences between the three most common Inconel alloys - Inconel 600, Inconel 601, and Inconel 625 - to assist engineers and purchasers in selecting the best material for their individual requirements.

Inconel 600, Inconel 601, and Inconel 625 are all nickel-based alloys that have been solid solution strengthened; however, their precise composition and strengthening technique varies.

What is solid solution strengthening?
Solid solution strengthening is the process of dissolving alloying elements (such as chromium, iron, molybdenum, etc.) into a metal matrix, modifying the matrixs lattice structure, increasing lattice distortion, and thereby increasing the alloys strength and hardness. This approach does not rely on precipitation strengthening, but rather on the interaction of alloying elements and matrix atoms, allowing the material to keep its strength at high temperatures.

Comparison of their solid solution mechanisms
Inconel 600: It is primarily a solid solution fortified by high nickel and chromium content (often 72% Ni and 14% Cr), resulting in a stable face-centered cubic lattice structure with good oxidation and corrosion resistance. Its strength stems mostly from the solid solution strengthening effect of nickel and chromium.

Inconel 601: In addition to the basic solid solution strengthening effect of nickel and chromium, Inconel 601 contains 1% aluminum, which can form a stable aluminum oxide protective layer at high temperatures to improve oxidation resistance, making it particularly suitable for high-temperature environments above 1000°C. The addition of aluminum strengthens the alloy, increasing its resistance to oxidation.

Inconel 625: It contains nickel, chromium, molybdenum, and niobium. The addition of molybdenum and niobium, in particular, strengthens the alloy as a composite. These constituents not only strengthen solid solutions, but they also improve the alloys corrosion resistance and strength at high temperatures. 625 outperforms 600 and 601 at high temperatures, particularly in corrosive conditions.

Comparison of Chemical Composition

Grade

Ni

Cr

Fe

C

Mn

P

S

Si

Cu

Al

Ti

Mo

Nb+Ta

Co

Inconel 600

72.00A

14.00-17.00

6.00-10.00

0.15

1.00

-

0.015

0.50

0.50

-

-

-

-

-

Inconel 601

58.00-63.00

21.00-25.00

Rest

0.10

1.00

-

0.015

0.50

1.00

1.00-1.70

-

-

-

-

Inconel 625

58.00

20.00-23.00

5.00

0.10

0.50

0.015

0.015

0.50

-

0.40

0.40

8.00-10.00

3.15-4.15

1.00

A: Nickel plus cobalt

Alloy 600: Mostly consisting of nickel and chromium, is good for high temperature oxidation resistance, but somewhat inferior to 601 and 625 in corrosion resistance.

Alloy 601: Improved oxidation resistance by adding aluminum and titanium, appropriate for usage in high-temperature and oxidizing situations

Alloy 601: In addition to high nickel and chromium, it contains molybdenum, niobium, and other elements, making its performance more outstanding in extreme corrosion and high temperature environments, particularly suitable for harsh working conditions such as seawater, chemicals, and flue gas desulfurization.

Comparison of Mechanical Properties
Mechanical properties at room temperature

Grade

Tensile Strength, MPa

Yield Strength, MPa

Elongation, %

Hardness

Inconel 600

550-650

205240

3040

195–220 HB

Inconel 601

600

240300

30

≤220 HB

Inconel 625

830–900

410450

4050

-


Inconel 600, Inconel 601, and Inconel 625 are nickel-based high-temperature alloys with outstanding corrosion resistance, however their performance varies depending on the environment.

 

Inconel 600

Inconel 601

Inconel 625

Oxidation resistance

Good high temperature oxidation resistance

Good high temperature oxidation resistance, especially in environments with drastic temperature changes

It can maintain its oxidation resistance for a long time in high temperature environments

Acid resistance

Good resistance to dilute sulfuric acid and concentrated sulfuric acid

Good corrosion resistance to a variety of acidic media, suitable for acidic environments at high temperatures

Especially good resistance to harsh chemicals such as sulfuric acid, hydrofluoric acid and phosphoric acid at high temperatures

Chloride corrosion resistance

Suitable for hydrochloric acid gas environments at medium temperatures

In chloride-containing environments, Inconel 601 has better corrosion resistance than Inconel 600, but not as good as Inconel 625

Excellent pitting resistance in seawater chloride environments


Alloy 600: Suitable for acidic and chloride environments at moderate temperatures, but not as corrosion resistant as Inconel 625 at high temperatures
Alloy 601: Suitable for high temperature acidic environments, but not as corrosion resistant as Inconel 625 in chloride environments Alloy 625: Suitable for harsh corrosive environments

A materials high temperature stability refers to its ability to keep its original physical, chemical, and structural qualities at high temperatures. Materials with good high temperature stability can effectively withstand adverse effects such as oxidation, corrosion, thermal expansion, and so on under high temperature circumstances, ensuring their performance and longevity.

High temperature stability often involves oxidation resistance, corrosion resistance, thermal expansion, thermal shock stability, and high temperature strength.

 

Inconel 600

Inconel 601

Inconel 625

Oxidation resistance

Excellent

Excellent

Excellent

Corrosion resistance

Excellent

Excellent

Excellent

Thermal expansion

Moderate

Normal

Normal

Thermal shock resistance

Good

Excellent

Good

High temperature strength

Good

Good

Excellent


Inconel 600, 601 and 625 each have their own advantages in terms of high temperature stability:
Alloy 600: Suitable for high temperature environments below 600°C
Alloy 601: Suitable for high temperature environments above 1000°C
Alloy 625: Suitable for high temperature environments in the medium temperature range (540-870°C)

Comparison of Processing and Manufacturing Characteristics

 

Inconel 600

Inconel 601

Inconel 625

Difficulty of cold working

Good

Moderate

Normal

Difficulty of welding

Good

Moderate

Normal


Inconel 600: Suitable for typical cold working procedures and conventional welding methods, such as TIG and MIG welding.

Inconel 601: Because of its higher chromium and aluminum content, the cold working performance is slightly lower to Inconel 600; the welding performance is equivalent to Inconel 600, but because to its high chromium content, stricter welding control may be required to prevent crack formation

Inconel 625:Because of its high strength and alloy content, the cold working performance is relatively poor, requiring higher processing forces and more sophisticated process control; special attention to heat input and welding process is required during welding to avoid the occurrence of thermal cracking and stress corrosion cracking.

Comparison of Typical Applications
Inconel 600, 601, and 625 are three nickel-based alloys that are widely utilized in high-temperature and corrosive situations. They are widely utilized in aerospace, chemical, nuclear energy, and other industries, including petrochemical equipment, nuclear power pipelines, aviation engines, and other applications.

Alloy 600: lye evaporator; heat treatment furnace radiation tube.
Alloy 601: gas turbine combustion chambers and heat treatment fixtures
Alloy 625: seawater heat exchanger, flue gas desulfurization system

How to choose material among Inconel 600, 601 and 625?

 

Inconel 600

Inconel 601

Inconel 625

Temperature

Room temperature and temperatures below 600°C

Wide temperature range, -253°C to 1300°C

Stable performance from 600°C to 980°C

Pressure

Suitable for medium pressure environments

Suitable for medium pressure environments

Suitable for high pressure environments

Budget

Low

Moderate

High

Inconel 600: Suitable for applications with limited budgets and high oxidation and corrosion resistance; an affordable alternative for conventional high-temperature corrosive situations.
Inconel 601: It is suited for medium-to-high-temperature static applications.
Inconel 625: It is ideal for projects requiring large resources and great performance, with long-term value in corrosive conditions.

Comparison of Equivalent Grades
UNS N06600   W.Nr. 2.4816  BS NA14   AFNOR NC15Fe   
UNS N06601   W.Nr. 2.4851  BS NA49   AFNOR NC23FeA
UNS N06625   W.Nr. 2.4856  BS NA21   AFNOR NC22DNb

We can provide Inconel 600, Inconel 601, Inconel 625, and other nickel alloy pipes in a wide range of diameters and lengths. Our pipes are meticulously manufactured and tested in line with ASTM/ASME standards, and the quality is guaranteed. If youre interested in our products, please contact us.
 
Inconel 600 Alloy Tube

Inconel 600 Alloy Tube

 
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