Hastelloy is a family of nickel-based superalloys known for their exceptional resistance to corrosion, particularly in harsh chemical environments. These alloys are designed to withstand the most severe conditions, including high temperatures, and environments rich in acids, chlorides, and other aggressive chemicals. The high levels of nickel and molybdenum in Hastelloy make it a preferred material in the chemical processing, power generation, and aerospace industries.
The most common Hastelloy grades include Hastelloy C-276, Hastelloy C-22, and Hastelloy B-2, each tailored for specific environments and applications. Hastelloy is known for offering unparalleled resistance to pitting, crevice corrosion, and stress-corrosion cracking.
Common Grades:
Specifications:
| Element | C-276 Composition (%) | C-22 Composition (%) | B-2 Composition (%) |
|---|---|---|---|
| Nickel (Ni) | 57% | 56% | Balance |
| Molybdenum (Mo) | 15-17% | 12.5-14.5% | 26-30% |
| Chromium (Cr) | 14.5-16.5% | 20-22.5% | 1% max |
| Iron (Fe) | 4-7% | 2-6% | 2% max |
| Tungsten (W) | 3-4.5% | 2.5-3.5% | – |
| Cobalt (Co) | 2.5% max | 2.5% max | – |
| Carbon (C) | 0.01% max | 0.015% max | 0.02% max |
The high nickel and molybdenum content in Hastelloy ensures excellent corrosion resistance, while the presence of chromium enhances its ability to resist oxidation in corrosive environments.
| Property | Hastelloy C-276 | Hastelloy C-22 | Hastelloy B-2 |
|---|---|---|---|
| Tensile Strength | 730 MPa | 760 MPa | 760 MPa |
| Yield Strength | 283 MPa | 310 MPa | 350 MPa |
| Elongation | 40% | 50% | 40% |
| Hardness | 200 HB | 225 HB | 205 HB |
These mechanical properties make Hastelloy strong and durable under extreme temperatures and pressure conditions.
Hastelloy is renowned for its superior resistance to corrosion in a variety of harsh environments:
Oxidizing and Reducing Acids: Hastelloy excels in environments containing hydrochloric, sulfuric, and hydrofluoric acids, making it ideal for chemical processing.
Chlorine-Containing Solutions: Both Hastelloy C-276 and C-22 provide excellent protection against chlorine and chlorine dioxide in wet and dry forms.
Pitting and Crevice Corrosion: The combination of high molybdenum and chromium content in Hastelloy makes it highly resistant to localized corrosion, such as pitting and crevice corrosion, in chloride-rich environments.
Stress-Corrosion Cracking: Hastelloy offers good resistance to stress-corrosion cracking, particularly in aggressive chemicals and seawater environments.
Sulfur Compounds: Hastelloy can withstand exposure to sulfur-based compounds, such as sulfuric acid and hydrogen sulfide.
Hastelloy alloys are used in a wide variety of industries that require excellent corrosion resistance and high strength, including:
Chemical Processing:
Aerospace Industry:
Power Generation:
Marine Applications:
Oil and Gas Industry:
Pharmaceutical Industry:
Excellent Corrosion Resistance:
High Temperature Strength:
Versatility:
Durability:
Good Weldability:
Hastelloy alloys can be machined and welded using conventional methods, though care must be taken due to their strength and tendency to work harden.
Hastelloy alloys are typically solution heat-treated to enhance corrosion resistance and mechanical properties. Heat treatment is performed at temperatures around 1150°C, followed by rapid quenching to preserve the alloy’s structure.
Chemical and Petrochemical: Hastelloy’s unparalleled corrosion resistance makes it a mainstay in reactors, heat exchangers, and valves in chemical processing plants.
Aerospace: Used in turbine blades, combustion chambers, and other components exposed to high temperatures and corrosive gases.
Power Generation: Found in nuclear and conventional power plants in tubing, heat exchangers, and boilers.
Oil and Gas: Hastelloy is critical for pipelines, wellheads, and equipment that encounter hydrogen sulfide and other corrosive substances.