Hastelloy C276
Complete analysis of Hastelloy C276 alloy (UNS N10276)
I. Implementation standards (classified by product form)
The technical specifications of Hastelloy C276 cover American standards (ASTM/ASME), European standards and national standards, targeting different product forms:
- Plates/strips: ASTM B575 / ASME SB575;
- Bars/forging billets: ASTM B574 / ASME SB574 (bars), ASTM B564 / ASME SB564 (forgings);
- Seamless pipes: ASTM B622 / ASME SB622;
- Welded pipes: ASTM B619 / B626 / ASME SB619 / SB626;
- Unified identification: UNS N10276 (American unified numbering system, core general standard).
II. Name and Code
- General name: Hastelloy C276;
- Authoritative grades:
- American standard: UNS N10276;
- European standard: W.Nr. 2.4819 (Germany), NiMo16Cr15W (component abbreviation);
- National standard: GB/T NS334 (Chinese corrosion – resistant alloy system).
III. Chemical composition (mass fraction,%, typical range of ASTM standard)
Hastelloy C276 is a nickel – chromium – molybdenum – tungsten – based super corrosion – resistant alloy, which resists extreme corrosion through the synergy of high Mo + W. Its composition is as follows:
| Element | Content Range | Core Function |
|---|---|---|
| Nickel (Ni) | ≈57 (balance) | Stabilizes the austenitic matrix and resists stress corrosion |
| Chromium (Cr) | 14.5 – 16.5 | Resists oxidation, pitting corrosion and crevice corrosion |
| Molybdenum (Mo) | 15.0 – 17.0 | Resists reducing media (sulfuric acid, hydrochloric acid) |
| Tungsten (W) | 3.0 – 4.5 | Strengthens resistance to chloride and humid chlorine gas corrosion |
| Iron (Fe) | ≤7.0 | Reduces cost and assists in strengthening |
| Cobalt (Co) | ≤2.5 | Impurity control (residual element, needs to be limited) |
| Carbon (C) | ≤0.01 | Avoids carbide precipitation and embrittlement |
| Manganese (Mn) | ≤1.0 | Improves hot working fluidity |
| Silicon (Si) | ≤0.08 | Optimizes casting/forging structure |
| Sulfur (S) | ≤0.01 | Inhibits hot working hot cracking tendency |
IV. Mechanical properties (solid solution treatment state, typical value at room temperature)
After solution treatment (water quenching/air cooling at 1010 – 1150°C), Hastelloy C276 combines medium – high strength and ultra – high plasticity, and can be stably used at -200 – 400°C:
| Performance Indicator | Typical Value (Solution State) | Remarks |
|---|---|---|
| Tensile Strength | ≥690 MPa | Can be further improved by cold working (e.g., reaches 800 MPa + after cold rolling) |
| Yield Strength (0.2%) | ≥283 MPa | Some standards require ≥355 MPa (need to be combined with specifications) |
| Elongation (%) | ≥40 | Excellent formability, supporting complex processing (rolling, welding) |
| Hardness (HB) | ≤210 | No age hardening (the austenitic matrix is stable, and aging has no obvious strengthening effect) |
V. Heat Treatment Requirements
- Core Process: Solution Treatment
- Temperature: 1010 – 1150°C (1050°C is commonly used, hold for 1 – 2 hours);
- Cooling: Water quenching or rapid air cooling (to ensure uniform solid solution of Mo and W, prevent the precipitation of brittle μ phase and avoid hot brittleness).
- Hot Working Key Points:
- Temperature: 1200 – 950°C (needs to quickly pass through the sensitization zone to avoid the precipitation of carbides/metal intermetallic phases at grain boundaries);
- Cooling: Water cooling immediately after processing (same as solution logic, inhibit the precipitation of harmful phases).
VI. Main application fields
Hastelloy C276, due to its “resistance to multi – element corrosion (oxidation + reduction + chloride ions) + wide – temperature stability”, focuses on extreme corrosion scenarios:
- Chemical Metallurgy:
- Sulfuric acid/hydrochloric acid production: Evaporators, heat exchangers (resistant to dilute sulfuric acid at ≤80°C and concentrated hydrochloric acid corrosion);
- Chlor – alkali industry: (electrolytic cells, chlorine pipelines, resistant to humid chlorine gas and hypochlorite corrosion).
- Environmental Protection Desulfurization:
- Flue gas desulfurization (FGD) system: (absorption towers, spray pipes, resistant to high Cl⁻ and SO₄²⁻ mixed corrosion, service life over 5 years).
- Marine Engineering:
- Seawater desalination equipment: (membrane shells, pipelines), offshore platform fasteners (resistant to seawater/salt spray, resistant to pitting/crevice corrosion).
- Oil and Natural Gas:
- Acid gas field pipelines: (containing H₂S/CO₂/Cl⁻), crude oil distillation towers (resistant to high – temperature corrosion).
- Special Scenarios:
- Pulp bleaching: (resistant to ClO₂ and chloride corrosion), pharmaceutical/food: (resistant to chemical cleaning agents and high – temperature sterilization).
Supplementary Characteristics
- Corrosion resistance advantage: One of the only alloys that can resist humid chlorine gas, chlorine dioxide, and high – concentration chlorides (FeCl₃, CuCl₂), and has extremely strong resistance to stress corrosion cracking (SCC);
- Weldability: ERNiCrMo – 4 welding wire (AWS A5.14) is recommended, and heat input should be controlled (≤1.5kJ/mm) to avoid hot cracking;
- Limitation: Not resistant to molten strong alkali (such as NaOH ≥300°C) and strong oxidizing acids (such as concentrated nitric acid + high – concentration Fe³⁺), and such environments should generally be avoided.
Hastelloy C276 is a “benchmark for universal corrosion – resistant alloys”, and its core competitiveness lies in the synergy of high Mo + W to resist extreme corrosion. When selecting materials, it is necessary to match standards and processing states based on medium type (oxidation/reduction), temperature, and stress level.