Overview
Monel 400, Monel K-500, Inconel 600, Inconel 625, Inconel 718, Inconel X-750, Incoloy 800, Incoloy 800H, Incoloy 825, Incoloy A-286 and Hastelloy C-276 are the most common nickel alloy grades. The chemical composition is as follows:
| Grade | S | Si | C | Mn | P | B | Al | Ti | Cu | Co | V | W | Nb | Ta | Mo | Fe | Cr | Ni |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Monel 400 | ≤0.024 | ≤0.5 | ≤0.3 | ≤2 | 28-34 | ≤2.5 | ≥63 | |||||||||||
| Monel K-500 | ≤0.01 | ≤0.5 | ≤0.25 | ≤1.5 | 2.3-3.15 | 0.35-0.85 | 27-33 | ≤2 | ≥63 | |||||||||
| Inconel 600 | ≤0.015 | ≤0.5 | ≤0.15 | ≤1 | ≤0.5 | 6-10 | 14-17 | ≥72 | ||||||||||
| Inconel 625 | ≤0.015 | ≤0.5 | ≤0.1 | ≤0.5 | ≤0.015 | ≤0.4 | ≤0.4 | ≤1 | 3.15-4.15 | 8-10 | ≤5 | 20-23 | ≥58 | |||||
| Inconel 718 | ≤0.015 | ≤0.35 | ≤0.08 | ≤0.35 | ≤0.015 | ≤0.006 | 0.2-0.8 | 0.65-1.15 | ≤0.3 | ≤1 | 4.75-5.5 | 2.8-3.3 | Bal. | 17-21 | 49-55 | |||
| Inconel X-750 | ≤0.01 | ≤0.5 | ≤0.08 | ≤1 | 0.4-1 | 2.25-2.75 | ≤0.3 | ≤0.5 | 0.7-1.2 | 5-9 | 14-17 | ≥70 | ||||||
| Incoloy 800 | ≤0.015 | ≤1 | ≤0.1 | ≤1.5 | 0.15-0.6 | 0.15-0.6 | ≤0.75 | ≥39.5 | 19-23 | 30-35 | ||||||||
| Incoloy 800H | ≤0.015 | ≤1 | 0.05-0.1 | ≤1.5 | 0.15-0.6 | 0.15-0.6 | ≤0.75 | ≥39.5 | 19-23 | 30-35 | ||||||||
| Incoloy 825 | ≤0.03 | ≤0.5 | ≤0.05 | ≤1 | ≤0.2 | 0.6-1.2 | 1.5-3 | 2.5-3.5 | ≥22 | 19.5-23.5 | 38-46 | |||||||
| Incoloy A-286 | ≤0.03 | ≤1 | ≤0.08 | ≤2 | 0.001-0.01 | ≤0.35 | 1.9-2.35 | 0.1-0.5 | 1-1.5 | Bal. | 13.5-16 | 24-27 | ||||||
| Hastelloy C-276 | ≤0.08 | ≤0.01 | ≤1 | ≤0.5 | ≤2.5 | ≤0.35 | ≈4 | ≈16 | ≈5 | ≈16 | ≈57 | |||||||
In this article, we will explore together the role and influence of different chemical elements in these grades.
The Role of Different Elements in Nickel Alloys
Nickel alloy is the most widely used and strongest type of superalloy. Nickel in the nickel alloy is an austenite stabilizing element, which can make the nickel alloy maintain the FCC structure so that it can dissolve more other alloying elements, while maintaining good structural stability and material plasticity.
Cr, Mo and Al play an anti-oxidation and anti-corrosion effect, and have a certain enhancement effect. The action modes of nickel alloy strengthening elements can be divided into the following three types:
Ⅰ. Solid Solution Strengthening Element
Because of the difference in atomic radius from the basic atoms, solid solution strengthening elements (such as W, Mo, Co, Cr, V and etc.,) can form local lattice strain in the Ni-Fe structure to achieve the effect of strengthening the material.
Ⅱ. Precipitation Strengthening Elements
Precipitation strengthening elements such as Al, Ti, Nb, Ta and etc., can form an integrated and ordered A3B type intermetallic compound, such as Ni3 (Al, Ti) and other strengthening phases (γ'), so that the alloy can be effectively strengthened and obtain higher high temperature strength than iron-based alloys and cobalt-based alloys.
Ⅲ. Grain Boundary Strengthening Elements
Grain boundary strengthening elements, such as B, Zr, Mg, rare earth elements and etc., can enhance the high temperature properties of the alloy.
The Difference Between Monel, Inconel, Incoloy and Hastelloy Grades
Generally, the grades of nickel alloys are named by the manufacturers who developed them. For example:
Ni-Cu alloys are also called Monel alloys, such as Monel 400 and Monel K-500.
400
Si
C
Mn
Fe
Cu
Ni
K-500
Si
C
Mn
Fe
Al
Ti
Cu
Ni
Ni-Cr alloys are generally called Inconel alloy, such as Inconel 600 and Inconel 625, which are common heat-resistant nickel alloys. They are mainly used under oxidizing medium conditions.
600
Si
C
Mn
Cu
Fe
Cr
Ni
625
Si
C
Al
Ti
Co
Ta
Mo
Fe
Cr
Ni
If a higher amount of iron is added to the Inconel alloys to replace nickel, they become the Incoloy alloys, such as Incoloy 800, Incoloy 825, etc. Their high temperature resistance is not as good as that of the precipitation hardening nickel alloy, but they are cheaper. They can be used in the lower temperature components of the jet engine and the reactor of petrochemical plants.
800
Si
C
Mn
Al
Ti
Cu
Fe
Cr
Ni
825
Si
Mn
Al
Ti
Cu
Mo
Fe
Cr
Ni
If precipitation strengthening elements (Ti, Al, Nb, etc.) are added to Inconel and Incoloy, they become precipitation hardening nickel alloys such as Inconel 718, Incoloy A-286 and etc., which can still maintain good mechanical strength and corrosion resistance at high temperatures. They are mostly used in jet engines components.
718
Si
C
Al
Ti
Co
Nb
Ta
Mo
Fe
Cr
Ni
A-286
Si
C
Mn
Al
Ti
V
Mo
Fe
Cr
Ni
The Ni-Cr-Mo(-W)(-Cu) alloy is called Hastelloy, in which Ni-Cr-Mo is mainly used under the conditions of reducing media corrosion. The representative grades of Hastelloy are Hastelloy C-276, C-2000, etc.
The following figure summarizes the element relationship between different nickel alloy grades for your reference:
C-276
Mn
Co
V
W
Fe
Mo
Cr
Ni
C-2000
Al
Cu
Co
Fe
Mo
Cr
Ni
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