Table of Contents
When it comes to choosing the right material for corrosion resistance and high-temperature applications, Alloy 20 and Hastelloy are two alloys frequently considered by engineers and designers. Each material offers distinct advantages depending on the environment in which they are used. In this article, we will compare Alloy 20 and Hastelloy, looking at their properties, applications, advantages, and limitations. By the end of this comparison, you will have a clear understanding of which material is better suited for your specific needs.
Overview of Alloy 20
Alloy 20 is a high-performance nickel-chromium-molybdenum alloy that is widely known for its resistance to sulfuric acid and other aggressive chemicals. Developed primarily for applications in the chemical processing industries, it combines good mechanical properties with excellent resistance to corrosion. Alloy 20 is also known for its ability to resist pitting, crevice corrosion, and stress corrosion cracking.
Overview of Hastelloy
Hastelloy is a family of corrosion-resistant metal alloys primarily composed of nickel, molybdenum, and chromium. These alloys are specifically designed to withstand extreme environments such as high-temperature and high-pressure conditions. Hastelloy alloys are known for their excellent resistance to oxidizing and reducing chemicals, making them ideal for industries such as chemical processing, aerospace, and energy production.
Composition Comparison
| Element | Alloy 20 | Hastelloy C-276 |
|---|---|---|
| Nickel | 32-38% | 57-63% |
| Chromium | 19-21% | 14-16% |
| Molybdenum | 3-4% | 15-17% |
| Iron | Iron balance | Iron balance |
| Other Elements | Carbon, manganese, silicon, phosphorus, sulfur | Carbon, silicon, tungsten |
Mechanical Properties Comparison
| Property | Alloy 20 | Hastelloy C-276 |
|---|---|---|
| Tensile Strength | 85-105 ksi | 100-130 ksi |
| Yield Strength | 30-50 ksi | 35-55 ksi |
| Elongation | 40% (in 2 inches) | 40% (in 2 inches) |
| Hardness | Rockwell B 85-95 | Rockwell B 85-95 |
Corrosion Resistance
Both Alloy 20 and Hastelloy are renowned for their corrosion resistance properties, particularly in aggressive environments. However, there are differences in their performance across various conditions:
- Alloy 20: Excellent resistance to sulfuric acid, phosphoric acid, and organic acids. It is also resistant to chloride stress corrosion cracking.
- Hastelloy: Offers superior resistance to a wide range of aggressive chemicals, including hydrochloric acid, chlorine, and high-temperature environments. It also resists oxidation and carburization in high-temperature settings.
Applications of Alloy 20
Alloy 20 is typically used in environments where resistance to sulfuric acid and other acidic solutions is required. Some common applications include:
- Chemical processing plants
- Pharmaceutical manufacturing
- Food and beverage processing equipment
- Flue gas desulfurization systems
Applications of Hastelloy
Hastelloy, particularly Hastelloy C-276, is used in industries that require extreme resistance to both high temperatures and aggressive chemicals. Some common applications include:
- Aerospace and aircraft manufacturing
- Marine environments
- Power generation
- Chemical processing in highly corrosive environments
Advantages of Alloy 20
- Superior resistance to sulfuric acid and similar chemicals
- Good mechanical properties at elevated temperatures
- Relatively cost-effective compared to other corrosion-resistant alloys
Advantages of Hastelloy
- Exceptional resistance to a wide range of chemicals, including oxidizing and reducing agents
- Excellent performance in high-temperature and high-pressure environments
- Superior resistance to pitting, crevice corrosion, and stress corrosion cracking
Cost Comparison
| Material | Cost (per kg) |
|---|---|
| Alloy 20 | $12 - $18 |
| Hastelloy C-276 | $60 - $100 |
Conclusion
Alloy 20 and Hastelloy are both excellent choices for applications requiring corrosion resistance, but they serve different needs. Alloy 20 is more cost-effective and suitable for environments involving sulfuric acid and other aggressive chemicals, while Hastelloy excels in high-temperature and high-pressure environments where superior corrosion resistance is required. The choice between the two materials should be based on the specific demands of the application, including factors such as cost, temperature, and the type of chemicals involved.
Related Questions:
1. What are the key differences in corrosion resistance between Alloy 20 and Hastelloy?
Alloy 20 is particularly resistant to sulfuric acid and other organic acids, while Hastelloy is more versatile, offering superior resistance to a wider range of chemicals, including hydrochloric acid and high-temperature environments.
2. Is Alloy 20 more cost-effective than Hastelloy?
Yes, Alloy 20 is generally more affordable than Hastelloy, making it a more cost-effective solution for many applications that require resistance to acids like sulfuric acid.
3. In what industries would Alloy 20 be the better choice over Hastelloy?
Alloy 20 is a better choice for industries like chemical processing, food and beverage processing, and pharmaceutical manufacturing, where resistance to sulfuric acid and similar chemicals is a priority.