Overview
Incoloy is a commonly used superalloy. It is widely used in aerospace, chemical, petroleum and other fields. When choosing materials, do you have the following questions:
The same nickel-chromium alloy, what is the difference between Incoloy and Inconel?
Why does Incoloy have so many grades?
Incoloy grades are named according to what rules?
In this article, we will introduce Incoloy from chemical composition, mechanical properties and physical properties. I believe it can solve most of your questions about Incoloy alloy.
What is Incoloy?
Incoloy alloy is a general term for a series of superalloys with high iron content. Depending on the ratio of nickel, chromium, and iron, Incoloy alloys can be nickel-iron-chromium alloys, iron-nickel-chromium alloys or iron-chromium-nickel alloys.
You can see that the Incoloy alloy has a high percentage of iron. To explain the reason clearly, we have to mention the relationship between Incoloy alloy and Inconel alloy.
Contrary to what many people think, although the performance of Incoloy is not as good as Inconel alloy, its development is actually later than the latter.
In the previous article, we mentioned that Inconel alloy belongs to nickel-chromium alloy. It has strong high temperature corrosion resistance. The Incoloy alloy is formed by adding a large amount of iron to the Inconel alloy.
In the context of the development of the Incoloy alloy, nickel is a very scarce strategic metal. Therefore, it was desired to have an alloy that had a lower nickel content but was equally resistant to high temperature corrosion. And Incoloy is the alloy that meets the demand. It uses a large amount of iron to replace nickel. Although its corrosion resistance is not as good as Inconel alloy, it is sufficient in many cases and has a lower cost.
All in all, Incoloy alloy is a nickel-saving Inconel alloy. It has a lower price than Inconel.
Chemical Composition of Incoloy
There are many grades of Incoloy alloy, which is mainly due to two reasons:
First of all, because Incoloy alloy sacrifices performance to a certain extent, it needs to focus on more subdivided performance for different fields. Therefore, different elements are added to Incoloy alloy to achieve different performance characteristics, and also form different grades.
Second, Incoloy alloy is a lower cost alloy. Different iron contents also form different grades of alloys. It gives people more choices at different costs.
Below are the common Incoloy grades:
Below, we will introduce the role of different elements in Incoloy alloy one by one.
Nickel
Nickel is the basis of all superalloys. Its role is to stabilize the austenite of the alloy. In addition, nickel element also has a certain corrosion resistance.
In Incoloy alloy, nickel is the main source of high temperature resistance. Since the nickel content of Incoloy alloy is often lower than that of other superalloys, its high-temperature resistance and corrosion resistance will also be lower than those of high-nickel alloys to a certain extent.
Iron
Iron occupies a large proportion in Incoloy alloy. Its role is mainly to reduce nickel content and save costs.
In Incoloy alloy, there is a part of iron-based superalloy. Iron exists as a matrix in this part of the alloy.
In addition, iron can play a small amount of solid solution strengthening in superalloys.
Chromium
Chromium is the main source of corrosion resistance for Incoloy alloys. Like stainless steel and other superalloys, chromium mainly plays an anti-oxidation role in the alloy. To compensate for the reduced corrosion resistance caused by the reduced nickel content, Incoloy alloys tend to have higher chromium content.
Chromium can also play a role of solid solution strengthening, improving the strength of the alloy to a certain extent.
Incoloy 890 is a typical grade with high chromium content.
Molybdenum
Molybdenum plays two main roles in Incoloy alloys: improving corrosion resistance and solid solution strengthening.
First of all, molybdenum is a good reduction-resistant metal, which can form a good supplement to corrosive environments where chromium cannot play a role.
Secondly, the atomic radius of molybdenum is very different from that of iron and nickel, and it has obvious solid solution strengthening effect.
In Incoloy alloys, the content of molybdenum is often not much, because the price of molybdenum metal is very high, contrary to the original intention of Incoloy to save costs. Incoloy 926 is a typical molybdenum-containing alloy.
Aluminum
Aluminum plays two roles in the Incoloy alloy.
First, in some Incoloy alloys (such as Incoloy 800), aluminum is added as a corrosion resistance element to compensate for the reduction of nickel.
Secondly, in some precipitation strengthening Incoloy alloys (such as Incoloy 925), aluminum exists as a precipitation strengthening element to greatly increase the strength of the alloy.
Titanium
The role of titanium in Incoloy alloys is similar to that of aluminum. Its main function is precipitation strengthening. In Incoloy A-286, titanium only needs to be combined with a small amount of aluminum to significantly increase the tensile strength of the alloy.
Niobium
Niobium acts as both solid solution strengthening and precipitation strengthening in the alloy. In Incoloy alloys, except for Incoloy 020, niobium is more regarded as a precipitation strengthening element. However, niobium will only appear in some high-end Incoloy alloys (such as Incoloy 945), because the price of niobium is very high.
Copper
Copper plays a major role in increasing corrosion resistance in Incoloy alloys. It can not only make up for the reduced basic corrosion resistance due to the reduced nickel content, but it can also effectively increase the alloy's resistance to sulfuric acid. Incoloy 825 is a typical copper-containing Incoloy alloy.
Vanadium
Vanadium occurs mainly in Incoloy A-286. It enhances the solid solution strengthening and precipitation strengthening of the alloy at the same time.
Silicon
Silicon is a unique element in Incoloy 330. Its main function is to replace a part of chromium to improve the oxidation resistance of this alloy. However, it is not suitable to add too much silicon, and it is also considered as a harmful element to reduce the performance of the alloy, which is why most alloys need to control the silicon content.
Cobalt
Cobalt is mainly found in low expansion alloys (Incoloy 903 & 907 & 909). It not only brings better high temperature resistance and strength, but also brings a larger low expansion temperature range. This element can significantly reduce the linear expansion coefficient of the alloy at high temperature.
Mechanical Properties of Incoloy
According to the distinction of microstructure, Incoloy alloys can be divided into two broad categories: solid solution strengthened alloys and precipitation strengthened alloys.
Among these two categories, precipitation strengthened alloys can obtain much higher strength than solid solution strengthened alloys through aging treatment. The table below compares the mechanical properties of two typical alloys:
| Alloy | Category | Tensile Strength | Yield Strength | Elongation |
|---|---|---|---|---|
| MPa | MPa | % | ||
| Incoloy 800 | Solid Solution Strengthened Alloy | 515 | 205 | 30 |
| Incoloy 825 | Solid Solution Strengthened Alloy | 586 | 241 | 30 |
| Incoloy 925 | Precipitation Strengthened Alloy | 965 | 758 | 18 |
| Incoloy A-286 | Precipitation Strengthened Alloy | 896 | 586 | 15 |
The two alloys are also distinguished in their nomenclature. Incoloy alloys starting with 8 are solid solution strengthening alloys, while Incoloy alloys starting with 9 are precipitation strengthening alloys. With this rule, you can have a more intuitive understanding of the properties of the alloy.
However, there are some special cases in the naming of Incoloy alloys. For example: Incoloy 926 is a solid solution strengthening alloy, and Incoloy A-286 is a precipitation strengthening alloy. All Incoloy alloys are organized according to classification below:
In actual material selection, if your project requires the alloy to withstand huge stress during work, precipitation strengthened alloys should be preferred. On the contrary, solid solution strengthening alloy should be selected.
Physical Properties of Incoloy
Due to the reduced nickel content and increased iron content of Incoloy alloy, it is also lower density than Inconel alloy. This also reduces the cost of Incoloy alloy to a certain extent. The following table compares the density of common Inconel alloys and Incoloy alloys:
| Inconel Grades | Density | Incoloy Grades | Density |
|---|---|---|---|
| Inconel 600 | 8.47 | Incoloy 800 | 7.94 |
| Inconel 625 | 8.44 | Incoloy 825 | 8.14 |
| Inconel 690 | 8.19 | Incoloy 890 | 7.94 |
| Inconel 725 | 8.31 | Incoloy 925 | 8.08 |
Density is an indispensable physical quantity if you need to calculate the weight of Incoloy alloy. You can quickly calculate the weight with the following tools:
FAQ
Under what circumstances can Incoloy alloy replace Inconel alloy?
This problem needs to be considered from two perspectives of high temperature resistance and corrosion resistance. First of all, the service temperature of Inconel alloy is often higher than that of Incoloy alloy. Second, Inconel alloys are resistant to corrosive environments that many Incoloy alloys cannot. Therefore, if your project needs to work at a higher temperature and in a harsher corrosive environment, we recommend that you choose Inconel alloy to ensure the smooth progress of the project. On the contrary, we recommend you to use Incoloy alloy to reduce the cost. For more specific high temperature resistance and corrosion resistance of these two alloys, you can refer to the following document:
special-metals-quick-reference-guide.pdf
Both are corrosion-resistant alloys with high iron content. What is the difference between Incoloy alloy and stainless steel?
Compared with stainless steel, Incoloy alloy has a higher nickel content. Although Incoloy alloy has a lot of iron content, it is still less than that of stainless steel. Therefore, Incoloy is superior to stainless steel both in high temperature resistance and corrosion resistance. Of course, its price is also more expensive than stainless steel. From the perspective of nickel-iron ratio, Incoloy alloy is between Inconel alloy and stainless steel. Therefore, its performance and price are also between them. However, there are some Incoloy alloys with a very high iron content, such as Incoloy 926, and the line between them and stainless steels tends to be blurred. They can be regarded as both stainless steel and superalloy. From the point of view of practical application, Incoloy alloy is more inclined to high temperature application and stainless steel is more inclined to normal temperature application.
What are the most commonly used Incoloy alloys?
The most commonly used Incoloy alloys are Incoloy 800 / 800H / 800HT, Incoloy 825, Incoloy 926, Incoloy A-286. You can visit the following links to view more specific information for each Incoloy alloy:
Incoloy Nickel Alloy -- Grades & Products
Further Reading
Conclusion
Incoloy is a superalloy with a high iron content. It can be regarded as an alloy with reduced nickel content on the basis of Inconel. Its price is cheaper than Inconel alloy. Therefore, it can replace some application scenarios of Inconel alloy at a lower cost.
We produce various Incoloy alloys for your choice. Any relevant needs can be communicated with us by email.
