Overview

Both nickel alloys and superalloys are high performance alloys.

According to different chemical composition ratios, these alloys are divided into many different grades.

Faced with all kinds of grades, people are often at a loss.

What is the difference between these grades? Which one should I use in my project?

If you have similar doubts, please be sure to read this article in its entirety. This article will explain in detail the selection criteria of nickel alloys and superalloys from five aspects.

Nickel Alloy and Superalloy

First of all, we need to simply understand the definitions and differences between nickel alloys and superalloys.

Nickel alloy refers to an alloy containing a large amount of nickel element. Nickel is an element with a certain corrosion resistance and a stable structure. Therefore, nickel alloys tend to have good corrosion resistance.

There are some nickel alloys that can be used at high temperatures (they are superalloys). However, some of these alloys are only suitable for room temperature. Therefore, not all nickel alloys are superalloys.

Superalloys are alloys used at high temperatures. Because nickel has a stable structure at high temperatures. Therefore, almost all superalloys contain some amount of nickel.

So, are all superalloys nickel alloys?

No. Superalloys can be divided into nickel-based superalloys, iron-based superalloys and cobalt-based superalloys according to the matrix.

The base elements in these alloys are nickel, iron and cobalt, respectively.

Only nickel-based superalloys are nickel alloys. Although iron-based superalloys and cobalt-based superalloys also contain nickel, their main components are still iron and cobalt.

The diagram below illustrates the relationship between nickel alloys and superalloys:

After understanding the basic concepts, let's discuss the specific principles of material selection.

Operating Temperature

In this section, we will tell you how to make preliminary material selection based on the temperature of the material.

The service temperature is the most critical factor when selecting an alloy. High temperature resistant alloys can be used at room temperature, but normal temperature alloys cannot be used at high temperatures. So this is the first step in our screening material.

As stated before, not all nickel alloys are suitable for high temperatures. But all superalloys can be used at high temperatures.

In superalloys, different grades also have different emphases. Some alloys focus on high temperature resistance. There are also some superalloys that require better corrosion resistance. Therefore, their high temperature performance will be reduced to a certain extent.

In general, these alloys are divided into normal temperature use, high temperature use and comprehensive use.

Comprehensive use means that the alloy can be used at both high temperature and normal temperature.

The table below organizes the different alloys.

When actually selecting materials, you need to make a broad selection based on the temperature of the materials used in your project.

Chemical Environment

After determining the temperature of use, the next important consideration in the selection is the chemical environment.

Although most nickel alloys and superalloys have good corrosion resistance. But the types of corrosion they can resist vary.

Corrosive environments can be broadly classified into oxidizing environments, reducing environments, and mixed environments.

When selecting materials, you need to first analyze which environment the material will be used in. Then choose the appropriate material according to the specific environment.

In the alloy, the greater the chromium content, the stronger the oxidation resistance of the alloy. The larger the molybdenum content of the alloy, the stronger the reduction resistance. According to this rule, you can roughly select materials that meet the standards.

In a mixed environment, both oxidative and reductive corrosion are possible. Therefore, you may want to consider alloys that have both a high chromium content and a high molybdenum content. They have comprehensive corrosion resistance properties.

In addition, the following table sorts out the applicable environment of common alloys. You can refer to it as a selection criterion:

Pressure

Next, we have to consider whether the alloy needs to withstand a lot of stress in the actual project.

For some container parts, they can withstand limited stress. Therefore, it is sufficient to only consider high temperature resistance and corrosion resistance.

But for some high-strength components (such as the blades of aircraft engines), they need to resist strong forces during use. Therefore, high temperature strength has become an important consideration.

Alloys can be divided into solid solution strengthened alloys and precipitation strengthened alloys according to the strengthening method.

Solid solution strengthened alloys are single-phase alloys. They have some strength, but still not enough for many high stress applications. They are therefore mainly used for container parts such as housings.

Precipitation strengthened alloys have one or two more strengthening phases than solid solution strengthened alloys. They can often be twice as strong. These alloys are therefore perfect for high strength applications.

The table below summarizes the strengthening types of different alloys.

Special Needs

When choosing materials, you may also have some special needs. for example:

You want the material not to increase in volume too much as the temperature increases. This requires the alloy to have a small coefficient of linear expansion. At this time, you should choose a low expansion superalloy.

If you need the alloy to work well at extreme high temperatures (even if it has low corrosion resistance), you can choose a dispersion strengthened superalloy.

In addition, there are some enhanced alloys, which enhance the characteristics of a certain aspect on the basis of the original alloy. The subscripts organize these alloys separately:

Price

After you have screened the alloys that meet your needs based on the above four points, the last thing you need to consider is the price.

If your project has strict material requirements, then unfortunately, price may not be a factor that you should consider.

If the performance of some low-priced alloys has met your needs, we recommend you to use them. They are a cost-effective option for you.

Of all three superalloys, cobalt-based superalloys are the most expensive. Nickel-based superalloys are moderately priced. Iron-based superalloys are the cheapest. for example:

For the Inconel series of nickel-based alloys, a lower-priced option is the Incoloy series of iron-based alloys. They are based on Inconel alloys with reduced nickel content and increased iron content. Although there is a certain decline in performance, the price has also been significantly reduced.

FAQ

Further Reading

Introduction of Cobalt-based Superalloys - The Choice for Extreme Environments

Introduction of Nickel-based Superalloys - First Choice for High Temperature Applications

What is Iron-based Superalloy? Which Characteristics does It have?

What is Dispersion Strengthening and What are the Dispersion Strengthening Alloys?

What is Precipitation Strengthening & Aging Treatment. Which Alloys need Aging Treatment?

What is Solid Solution? Why do Nickel Alloy / Superalloy need Solution Treatment?

Clearly Understand the Important Roles of Molybdenum in Nickel Alloys

Clearly Understand the 4 Roles of Chromium in Superalloys

Clearly Understand the Role of Nickel in All 3 Types of Superalloys

Conclusion

When choosing alloy materials, you need to consider the following five aspects:

Operating temperature, chemical environment, stress, special needs and price.

In most cases, temperature, environment and pressure are important considerations.

If your project has low expansion, extreme high temperatures, or other special needs, there are some special superalloys you might consider.

Finally, you should choose materials with the lowest price as much as possible to optimize your budget while meeting your needs.

When you have finished selecting materials, we believe that you need to calculate the specific price of materials and make purchases. We are the most professional nickel alloy/superalloy supplier in China. Please contact us for any inquiries. Our sales will give you the best service.