What is the Difference Between Hastelloy X and Hastelloy C?

Nickel-based alloys are widely used in industries that require materials with outstanding strength, oxidation resistance, and corrosion resistance. Among these, Hastelloy alloys have earned a reputation for reliability in the harshest environments. Two notable grades are Hastelloy X and Hastelloy C-series alloys. While both belong to the same family, they have distinct chemical compositions, mechanical properties, and application fields.

This article explores in detail the difference between Hastelloy X and Hastelloy C, helping engineers, buyers, and manufacturers choose the right material for their specific applications.

1. What is Hastelloy?

Hastelloy is a trademarked name for a group of corrosion-resistant metal alloys primarily based on nickel, with varying additions of molybdenum, iron, cobalt, and chromium. These alloys are known for:

  • Exceptional resistance to corrosion and oxidation.

  • High mechanical strength at elevated temperatures.

  • Suitability for chemical processing, aerospace, and marine industries.

2. Overview of Hastelloy X

Hastelloy X is a nickel-iron-chromium-molybdenum alloy specifically designed for oxidation resistance and high-temperature strength.

Key Composition (approximate):

  • Nickel: 47%

  • Chromium: 22%

  • Iron: 18%

  • Molybdenum: 9%

  • Minor additions: Tungsten, cobalt

Key Features:

  • Excellent oxidation resistance up to 1200°C.

  • High creep and rupture strength at elevated temperatures.

  • Good resistance to stress corrosion cracking.

Common Applications:

  • Gas turbine engines.

  • Combustion chambers.

  • Jet engine afterburners.

  • Industrial furnaces and heat-treating equipment.

Hastelloy X is primarily chosen where high-temperature stability is required.

3. Overview of Hastelloy C Alloys

The Hastelloy C family includes grades such as Hastelloy C-22, C-276, and C-2000. These are nickel-molybdenum-chromium alloys with different enhancements.

Key Composition (C-276 as example):

  • Nickel: ~57%

  • Molybdenum: 16%

  • Chromium: 16%

  • Iron: 5%

  • Tungsten: 4%

Key Features:

  • Exceptional resistance to strong oxidizing and reducing chemicals.

  • Excellent resistance to pitting, crevice corrosion, and stress corrosion cracking.

  • Performs well in both oxidizing and reducing environments.

Common Applications:

  • Chemical processing industries.

  • Pollution control equipment.

  • Flue gas scrubbers.

  • Pulp and paper bleaching plants.

  • Pharmaceutical equipment.

Hastelloy C alloys are chosen for corrosion resistance in aggressive chemical environments.

4. Chemical Composition Comparison

Element Hastelloy X Hastelloy C-276
Nickel (Ni) ~47% ~57%
Chromium (Cr) ~22% ~16%
Molybdenum (Mo) ~9% ~16%
Iron (Fe) ~18% ~5%
Tungsten (W) Minor ~4%
Cobalt (Co) Minor —

The higher molybdenum in Hastelloy C alloys gives better corrosion resistance, while the higher iron and chromium in Hastelloy X enhances oxidation resistance at high temperatures.

5. Mechanical Properties

  • Hastelloy X: Strong mechanical performance at high temperatures, with high creep and rupture resistance.

  • Hastelloy C: Excellent corrosion resistance across a broad temperature range, but slightly lower high-temperature mechanical strength compared to Hastelloy X.

6. Oxidation and Corrosion Resistance

  • Hastelloy X: Outstanding oxidation resistance up to 1200°C, making it ideal for aerospace and furnace applications. However, it is less effective in strong reducing acids.

  • Hastelloy C: Superior corrosion resistance in chloride-containing environments, sulfuric acid, hydrochloric acid, and wet chlorine gas. It is the go-to alloy for chemical industries.

7. Applications Comparison

Hastelloy X

  • Aerospace engines.

  • Gas turbine combustors.

  • Heat-treating equipment.

  • Furnace rolls.

Hastelloy C Alloys

  • Chemical reactors and vessels.

  • Piping and valves in chemical plants.

  • Scrubbers and pollution control systems.

  • Marine and offshore equipment.

8. Cost Differences

  • Hastelloy X: Typically less expensive than Hastelloy C alloys due to lower molybdenum content.

  • Hastelloy C: Higher cost because of high nickel and molybdenum percentages, but justified by superior corrosion resistance.

9. Industry Standards

  • Hastelloy X: ASTM B435 (plate, sheet), ASTM B572 (wire), ASTM B619/B622 (pipe and tube).

  • Hastelloy C-276: ASTM B575 (plate, sheet), ASTM B574 (bar), ASTM B619/B622 (pipe and tube).

Suppliers like sasaalloy ensure products comply with these international standards.

10. Choosing the Right Alloy

  • Select Hastelloy X if:

    • The application involves high temperatures and oxidation exposure.

    • You need durability in aerospace or furnace environments.

  • Select Hastelloy C if:

    • The environment involves strong acids, chlorides, or mixed corrosive conditions.

    • The application is in the chemical processing or pollution control industry.

11. Advantages of Each

Hastelloy X

  • High-temperature performance.

  • Oxidation resistance.

  • Strong mechanical stability under stress.

Hastelloy C

  • Outstanding chemical corrosion resistance.

  • Versatility in oxidizing and reducing environments.

  • Resistance to localized corrosion.

12. Future Trends

  • Advanced aerospace alloys: Improved Hastelloy X variations for next-generation jet engines.

  • Environmental technologies: Increased use of Hastelloy C alloys in flue gas desulfurization and green chemical processing.

  • Hybrid applications: Use of both alloys in combined environments requiring high temperature and corrosion resistance.

13. Common Mistakes to Avoid

  • Using Hastelloy X in chemical plants where corrosion resistance is critical.

  • Selecting Hastelloy C for extreme high-temperature oxidation conditions.

  • Ignoring standards and certifications when sourcing alloys.

  • Overlooking total lifecycle costs — cheaper alloys may result in higher maintenance.

Conclusion

The difference between Hastelloy X and Hastelloy C lies in their composition, properties, and application focus. Hastelloy X is tailored for oxidation resistance and mechanical strength at high temperatures, making it ideal for aerospace and heat-treatment industries. Hastelloy C alloys, on the other hand, excel in corrosion resistance against aggressive chemicals, dominating chemical processing and pollution control applications.

Choosing the right alloy depends on your operational environment, required performance, and budget. By working with certified suppliers like sasaalloy, companies can ensure access to high-quality materials that meet international standards, guaranteeing safety, performance, and longevity.

Both alloys remain indispensable in industries that demand reliability under extreme conditions, and their complementary strengths make them essential for different engineering challenges.

Post time: Sep-03-2025