The nickel based superalloys are high-performance materials.
These alloys are divided into various grades based on their chemical composition ratios.
With so many grades available, it can be challenging to determine the differences and decide which one is suitable for your project.
What distinguishes these grades from each other? Which grade is the best choice for your specific needs?
If you have these questions, be sure to read this entire article. We will comprehensively explain the selection criteria for nickel based superalloys, covering all aspects to help you make an informed decision.
Contents
ToggleWhat are nickel based superalloys?
A nickel-based alloy is an alloy that contains a significant amount of nickel. Nickel is known for its corrosion resistance and stable structure, which gives nickel alloys their excellent corrosion resistance.
Some nickel alloys are designed for high-temperature applications, classifying them as superalloys. However, not all nickel alloys are suitable for high-temperature use; some are only appropriate for room temperature. Thus, not all nickel alloys qualify as superalloys.
Superalloys are specifically engineered for high-temperature use, and because of nickel’s stable structure at elevated temperatures, nearly all superalloys contain a substantial amount of nickel.
Choose According to Operating Temperature
In this section, we will guide you on how to make an initial material selection based on the operating temperature.
Service temperature is the most critical factor when choosing an alloy. High-temperature resistant alloys can also be used at room temperature, but room temperature alloys cannot withstand high temperatures. Therefore, this is the first step in our material selection process.
As mentioned earlier, not all nickel alloys are suitable for high temperatures, but all superalloys can withstand high-temperature conditions.
Among superalloys, different grades emphasize different properties. Some focus primarily on high-temperature resistance, while others are designed to offer better corrosion resistance, which can slightly reduce their high-temperature performance.
Generally, these alloys are categorized into those for normal temperature use, high-temperature use, and comprehensive use.
Comprehensive use means the alloy is suitable for both high-temperature and normal temperature applications.
Normal Temperature Use | Monel Alloys |
High Temperature Use | Inconel 600, Inconel 601, Inconel 617, Inconel 625, Inconel 625LCF, Inconel 690, Incoloy 800, Incoloy 800H, Incoloy 800HT, Incoloy 803, Incoloy 840, Incoloy 890, Hastelloy X |
Comprehensive Use | Other Inconel, Incoloy & Hastelloy Alloys |
Choose According to Chemical Environment
Once you’ve determined the operating temperature, the next crucial factor in material selection is the chemical environment.
While most nickel alloys and superalloys exhibit good corrosion resistance, their ability to resist different types of corrosion varies.
Corrosive environments are generally categorized as oxidizing, reducing, or mixed.
When choosing materials, it’s essential to analyze the specific environment where the material will be used. Then, select the appropriate alloy based on its resistance to that particular environment.
In alloys, higher chromium content enhances oxidation resistance, while increased molybdenum content improves resistance to reduction. Following this guideline helps in identifying materials that meet specific standards.
In mixed environments where both oxidative and reductive corrosion can occur, alloys with high chromium and molybdenum contents should be considered. These alloys offer comprehensive corrosion resistance properties.
Corrosion | Sulfuric Acid | Hydrochloric Acid | Hydrofluoric Acid | Phosphoric Acid | Nitric Acid | Organic Acids | Alkalies and Salts | Seawater |
Monel 400 | Excellent | Acceptable | Excellent | Excellent | Excellent | Excellent | Excellent | |
Monel R-405 | Excellent | Acceptable | Excellent | Excellent | Excellent | Excellent | Excellent | |
Monel K-500 | Excellent | Acceptable | Excellent | Excellent | Excellent | Excellent | Excellent | |
Inconel 600 | Acceptable | Acceptable | Acceptable | Excellent | Excellent | Acceptable | ||
Inconel 625 | Excellent | Excellent | Excellent | Excellent | Excellent | Excellent | Excellent | Excellent |
Inconel 625LCF | Excellent | Excellent | Excellent | Excellent | Excellent | Excellent | Excellent | Excellent |
Inconel 686 | Excellent | Excellent | Excellent | Excellent | Excellent | Excellent | Excellent | Excellent |
Inconel 690 | Acceptable | Acceptable | Excellent | Excellent | Excellent | Excellent | Excellent | Acceptable |
Incoloy 800 | Acceptable | Acceptable | Excellent | Excellent | Acceptable | |||
Incoloy 825 | Excellent | Excellent | Excellent | Excellent | Excellent | Excellent | Excellent | Excellent |
Incoloy 864 | Acceptable | Acceptable | Acceptable | Acceptable | Excellent | Excellent | Excellent | Excellent |
Incoloy 020 | Excellent | Excellent | Excellent | Excellent | Excellent | Excellent | Excellent | Excellent |
Incoloy 25-6HN | Excellent | Excellent | Acceptable | Excellent | Excellent | Excellent | Excellent | Excellent |
Hastelloy C-22 | Excellent | Excellent | Excellent | Excellent | Excellent | Excellent | Excellent | Excellent |
Hastelloy C-276 | Excellent | Excellent | Excellent | Excellent | Acceptable | Excellent | Excellent | Excellent |
Hastelloy G-3 | Excellent | Excellent | Excellent | Excellent | Excellent | Excellent | Excellent | Excellent |
Choose According to Pressure
Next, we need to assess whether the alloy will be subjected to significant stress in the intended application.
For certain structural components, such as containers, which endure moderate stress, considerations primarily revolve around high temperature and corrosion resistance.
However, for high-stress components like aircraft engine blades, which face substantial forces in operation, high temperature strength becomes critical.
Alloys are categorized into solid solution strengthened alloys and precipitation strengthened alloys based on their strengthening mechanisms.
Solid solution strengthened alloys consist of a single phase and offer moderate strength, suitable primarily for container parts such as housings.
In contrast, precipitation strengthened alloys incorporate one or more additional strengthening phases beyond solid solution alloys, often doubling their strength. These alloys are ideal for applications requiring high mechanical strength.
Type | Alloy |
---|---|
Solid Solution Strengthened Alloys | Monel 400 Series Inconel 600 Series Incoloy 800 Series Incoloy 926 Hastelloy Series (except Hastelloy C-22HS) |
Precipitation Strengthened Alloys | Monel 500 Series Inconel 700 Series Incoloy 900 Series (except Incoloy 926) Hastelloy C-22HS |
Choose According to Special Needs
When choosing nickel alloy 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.
Type | Alloy |
---|---|
Low Expansion Superalloy | Incoloy 903 Incoloy 907 Incoloy 908 Incoloy 909 Inconel 783 |
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.
Type | Alloy |
---|---|
Dispersion Strengthened Superalloy | Incoloy MA956 Inconel MA754 Inconel MA758 |
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:
Alloy | Feature |
---|---|
Monel R-405 | Free-machining Version of Monel 400 |
Inconel 601GC | Grain-control Version of Inconel 601 |
Inconel 625LCF | Fatigue-resistant, Bellows-quality Version of Inconel 625 |
Inconel 718SPF | Superplastic Forming Version of Inconel 718 |
Incoloy 800H | High-carbon Version of Incoloy 800 |
Incoloy 800HT | Creep Resistance Version of Incoloy 800H |
Hastelloy C-22HS | Precipitation Strengthening Version of Hastelloy C-22 |
Choose According to Cost
Once you have identified alloys that meet your requirements based on the above considerations, the final aspect to evaluate is the cost.
If your project demands stringent material specifications, price may unfortunately not be a flexible factor to consider.
However, if lower-cost alloys meet your performance requirements, we recommend using them as they offer a cost-effective solution.
Among superalloys, cobalt-based superalloys are the most expensive, while nickel-based superalloys are moderately priced. Iron-based superalloys are the least expensive. For instance:
In the nickel-based Inconel series, an economical alternative is the iron-based Incoloy series. These alloys are derived from Inconel with reduced nickel content and increased iron content. Although their performance may slightly diminish, the price is significantly lower.
FAQs
1.What is the difference between superalloy and stainless steel?
Stainless steel is mainly used at room temperature. Superalloys are mainly used at high temperatures. The corrosion resistance, high temperature resistance and strength of superalloys are higher than the former.
2.Which materials are more commonly used in practice?
Based on our experience, here are the ten most frequently used materials:
– Monel 400
– Inconel 600
– Inconel 625
– Inconel 718
– Incoloy 800
– Incoloy 800H
– Incoloy 825
– Incoloy A-286
– Hastelloy C-276
– Hastelloy C-22
Conclusion
When selecting alloy materials, it’s essential to consider the following five aspects: operating temperature, chemical environment, stress requirements, special needs, and cost.
Typically, temperature, environment, and stress are crucial factors in decision-making.
For projects demanding low thermal expansion, extreme high temperatures, or other specialized requirements, there are specific superalloys worth considering.
Lastly, prioritize materials that offer optimal performance at the lowest possible cost to effectively manage your budget while meeting project requirements.
Once material selection is complete, calculating the precise costs and making procurement decisions is the next step.
As the leading supplier of nickel-based superalloys in China, we ensure top-notch service. Feel free to contact us with any inquiries, and our sales team will provide you with exceptional assistance.