Heat Treatment of Hastelloy X

Hastelloy X is a high-temperature nickel-based alloy known for its exceptional strength, oxidation resistance, and excellent fabricability. To fully optimize its mechanical properties, Hastelloy X undergoes specific heat treatment processes.

In this blog post, we will explore the heat treatment methods used for Hastelloy X and their impact on the alloy’s performance at elevated temperatures.

Hastelloy-X Material Specification

The chemical composition of the alloy consists of the following elements:

  • Nickel: 47% (major component)
  • Chromium: 22%
  • Iron: 18%
  • Molybdenum: 9%
  • Cobalt: 1.5%
  • Tungsten: 0.6%
  • Carbon: 0.1%
  • Manganese: Maximum 1%
  • Silicon: Maximum 1%
  • Boron: Maximum 0.008%
  • Niobium: Maximum 0.5%
  • Aluminum: Maximum 0.5%
  • Titanium: Maximum 0.15%

Hastelloy-X Chemical Compositions

Hastelloy-X, also known as HASTELLOY® X, is a material that is specified and regulated by various industry standards and specifications. Here are the relevant specifications for Hastelloy-X:

  1. ASME Specifications:
    HASTELLOY® X is covered by ASME Section VIII, Division 1. Different forms of the material such as plate, sheet, strip, bar, forging, tubing, pipe, and fittings are covered by specific ASME specifications:
  • Plate, sheet, strip: ASME SB 435, ASTM B 435
  • Bar, forging: ASME SB 572, ASTM B 572
  • Tubing: ASME SB 619, ASTM B 619
  • Pipe: ASME SB 622, ASTM B 622
  • Fittings: ASME SB 366, ASTM B 366
  1. UNS Number:
    The UNS (Unified Numbering System) number assigned to Hastelloy-X is N06002. This provides a unique identification for the alloy in various industry standards and databases.
  2. DIN Designations:
    Hastelloy-X is assigned DIN designations as well. The DIN designations for Hastelloy-X are No. 2.4665 and NiCr22Fe18Mo. These designations are used in European and international standards and specifications.
  3. AMS Specifications:
    Certain forms of Hastelloy-X are also covered by AMS (Aerospace Material Specifications) specifications:
  • Sheet, strip, and plate: AMS 5536
  • Billet and bar: AMS 5754
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These specifications define the specific requirements and properties of Hastelloy-X, ensuring consistency and quality in its manufacturing, fabrication, and use across different industries.

Solution Treatment of Hastelloy X

The heat treatment process for Hastelloy X typically begins with a solution treatment. The alloy is heated to a temperature range of 2050°F to 2150°F (1121°C to 1177°C) followed by a rapid cooling process.

This solution treatment dissolves any precipitates and promotes the formation of a uniform microstructure, enhancing the material’s high-temperature strength and corrosion resistance.

Stabilization Treatment of Hastelloy X

After the solution treatment, Hastelloy X is often subjected to a stabilization treatment. This step involves heating the alloy in the range of 1850°F to 2050°F (1010°C to 1121°C) for a specific duration, followed by air cooling or furnace cooling.

Stabilization treatment further enhances the alloy’s high-temperature strength and provides improved resistance to sensitization, reducing the risk of intergranular corrosion.

Age Hardening Treatment of Hastelloy X

To further improve the mechanical properties of Hastelloy X, an age hardening treatment may be employed. This treatment involves heating the alloy to a temperature range of 1600°F to 1900°F (871°C to 1038°C) for a specific duration, followed by air cooling or furnace cooling.

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Age hardening helps to precipitate fine gamma prime (γ’) and gamma double prime (γ”) phases, resulting in increased strength, hardness, and creep resistance at elevated temperatures.

Effects of Heat Treatment on Hastelloy X

The heat treatment processes applied to Hastelloy X significantly impact its mechanical properties and performance at high temperatures. Proper solution treatment ensures a uniform microstructure, while stabilization treatment reduces the susceptibility to intergranular corrosion.

Age hardening treatment further enhances the alloy’s strength and resistance to creep deformation, making it suitable for demanding high-temperature applications.

Applications of Hastelloy X

Hastelloy X alloy finds extensive applications in various industries due to its exceptional properties. Here are some notable applications of Hastelloy X:

  1. Gas Turbine Engines:
    Hastelloy X alloy is widely used in gas turbine engines, particularly in combustion zone components. It is employed in transition ducts, combustor cans, spray bars, flame holders, afterburners, tailpipes, and cabin heaters. Its high-temperature strength, oxidation resistance, and excellent fabricability make it suitable for these critical components.
  2. Industrial Furnaces:
    Due to its remarkable resistance to oxidizing, reducing, and neutral atmospheres, Hastelloy X is recommended for use in industrial furnace applications. It exhibits exceptional performance even at high temperatures. Furnace rolls made from Hastelloy X have demonstrated excellent durability, remaining in good condition after operating for extended periods at temperatures up to 2150°F (1177°C).
  3. Chemical Process Industry:
    Hastelloy X alloy is extensively utilized in the chemical process industry for various applications. It is employed in retorts, muffles, catalyst support grids, and furnace baffles. The alloy’s resistance to corrosive environments and high-temperature stability make it suitable for these demanding chemical processing operations.
  4. Tubing for Pyrolysis Operations:
    In pyrolysis operations, where materials are subjected to high temperatures for thermal decomposition, Hastelloy X tubing is commonly employed. The alloy’s excellent heat resistance and resistance to oxidation enable it to withstand the harsh conditions of pyrolysis processes.
  5. Flash Drier Components:
    Hastelloy X is also utilized in the construction of flash drier components. Flash driers are used in various industries for rapid drying of materials. The alloy’s high-temperature strength, corrosion resistance, and durability make it suitable for withstanding the demanding operating conditions of flash drier systems.
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In summary, Hastelloy X alloy finds applications in gas turbine engines, industrial furnaces, the chemical process industry, pyrolysis operations, and flash drier systems. Its exceptional properties, including high-temperature strength, oxidation resistance, and corrosion resistance, make it a preferred choice for critical components in these industries.


Heat treatment plays a vital role in optimizing the performance and properties of Hastelloy X. Through solution treatment, stabilization treatment, and age hardening, the alloy’s high-temperature strength, corrosion resistance, and creep resistance can be enhanced.

Hastelloy X continues to be a favored material for applications in gas turbines, aircraft engines, industrial furnaces, and other high-temperature environments, thanks to its exceptional properties achieved through effective heat treatment processes.