Summary of the performance of different grades of Hastelloy (Hastelloy C alloy, such as C-276, C-22, C-2000, etc.)
Hastelloy, Hastelloy C alloy is a high-performance nickel-based corrosion-resistant alloy, belonging to the Hastelloy series (developed by Hastelloy International, USA), mainly used in extremely corrosive environments. Different grades of Hastelloy C alloy (such as C-276, C-22, C-2000, etc.) have slight differences in composition and performance, but are all known for their excellent corrosion resistance and high temperature stability. The following is a detailed introduction using Hastelloy C-276 as an example:
1. Chemical composition (typical value, wt%)
- Nickel (Ni): balance (about 57%)
- Chromium (Cr): 14.5–16.5% (enhanced oxidation resistance)
- Molybdenum (Mo): 15–17% (resistance to corrosion by reducing media)
- Tungsten (W): 3–4.5% (enhanced corrosion resistance)
- Iron (Fe): 4–7%
- Cobalt (Co): ≤2.5%
- Carbon (C): ≤0.01% (low carbon design reduces intergranular corrosion)
- Others: small amounts of manganese, silicon, vanadium, etc., extremely low sulfur and phosphorus impurities
2. Physical properties
- Density: about 8.89 g/cm³
- Melting point: 1325–1370°C
- Thermal expansion coefficient: 12.6 μm/m·°C (20–100°C)
- Thermal conductivity: 10.1 W/m·K (100°C)
3. Mechanical properties
- Tensile strength (room temperature): ≥690 MPa
- Yield strength (room temperature): ≥283 MPa
- Elongation (room temperature): ≥40%
- Hardness: ≤100 HRB (annealed state)
4. Corrosion resistance
- Typical corrosion resistance environment:
- Strong oxidizing acid (such as a mixture of concentrated sulfuric acid, nitric acid and hydrochloric acid)
- Reducing medium (such as an acid solution containing Cl⁻)
- Wet chlorine, hypochlorite
- High temperature sulfur-containing gas (such as H₂S)
- Pitting resistance (PREN): High molybdenum content gives excellent resistance to pitting and crevice corrosion.
- Intergranular corrosion resistance: Low carbon design and addition of stabilizing elements (such as tungsten) reduce the risk of sensitization.
5. Application areas
- Chemical industry: reactors, heat exchangers, pumps and valves (handling sulfuric acid, hydrochloric acid, phosphoric acid, etc.).
- Oil and gas: acidic oil and gas field equipment (resistant to H₂S, CO₂ corrosion).
- Environmental engineering: flue gas desulfurization (FGD) system, wastewater treatment equipment.
- Nuclear industry: corrosive medium containers in nuclear fuel reprocessing.
6. Processing and welding
- Cold/hot processing: The processing temperature and speed need to be controlled to avoid stress concentration.
- Welding: TIG welding (tungsten inert gas welding) is recommended, using matching welding wire (such as ERNiCrMo-4).
- Post-weld treatment: Usually no heat treatment is required, but the weld area needs to be cleaned to avoid impurity contamination.
7. Common grades comparison
- Hastelloy C-276: UNS N10276 (ASTM B575, B574, etc.).
- Hastelloy C-22: UNS N06022 (higher chromium content, better oxidation resistance).
- Hastelloy C-2000: UNS N06200 (containing copper, further expanding the corrosion resistance range).
8. Precautions
- Avoid high temperature sensitization: long-term exposure to 425–870°C may reduce intergranular corrosion resistance.
- Selection suggestions: Select the appropriate grade according to the specific corrosive medium (concentration, temperature, redox conditions).
Hastelloy C alloy has become one of the "ultimate anti-corrosion materials" in the fields of chemical industry, energy, etc. due to its reliability in harsh environments.
