Hastelloy C-4 alloy,C-4 alloy,UNS N06455; 1

### **Introduction to Hastelloy® C-4® (UNS N06455) Nickel Alloy** **Hastelloy® C-4®** is a nickel-chromium-molybdenum alloy specifically designed for exceptional thermal stability and resistance to a wide range of corrosive chemicals. Developed as an improvement over earlier C-type alloys, its primary advantage lies in its superior resistance to **sensitization and intermetallic phase formation** when exposed to high temperatures in the 1200°F - 1600°F (650°C - 870°C) range. This stability is achieved through a carefully controlled low-carbon, low-silicon chemistry and the addition of titanium, which stabilizes the alloy against the precipitation of grain boundary carbides. This makes C-4 particularly suitable for applications in the chemical process industry where equipment is subjected to both high temperatures and aggressive corrosive environments. --- ### **Chemical Composition (Weight %, typical per ASTM/ASME specifications)** The composition is optimized for thermal stability while maintaining excellent corrosion resistance. | Element | Minimum | Maximum | Key Function | | :--- | :--- | :--- | :--- | | **Nickel (Ni)** | **Balance** | | Forms the stable, corrosion-resistant austenitic matrix. | | **Chromium (Cr)** | 14.0 | 18.0 | Provides resistance to oxidizing media. | | **Molybdenum (Mo)** | 14.0 | 17.0 | Provides resistance to reducing media and pitting/crevice corrosion. | | **Iron (Fe)** | - | 3.0 | Kept low to optimize corrosion resistance. | | **Titanium (Ti)** | 0.70 | - | **Key stabilizer:** Prevents sensitization by forming stable carbides, minimizing chromium carbide precipitation at grain boundaries. | | **Cobalt (Co)** | - | 2.0 | - | | **Manganese (Mn)** | - | 1.0 | - | | **Silicon (Si)** | - | 0.08 | Kept very low to prevent segregation and formation of low-melting phases. | | **Carbon (C)** | - | 0.015 | Kept extremely low to minimize carbide precipitation. | | **Sulfur (S)** | - | 0.030 | - | ***Key Differentiator:*** The combination of **very low C and Si with Ti stabilization** is the defining feature that grants C-4 its exceptional thermal stability compared to its predecessors. --- ### **Physical Properties (Typical)** * **Density:** 8.64 g/cm³ (0.312 lb/in³) * **Melting Range:** 1330 - 1380 °C (2425 - 2515 °F) * **Thermal Expansion Coefficient:** 11.9 μm/m·°C (20-100°C) * **Thermal Conductivity:** 10.8 W/m·K at 100°C * **Modulus of Elasticity (Young's Modulus):** 217 GPa (31.5 x 10⁶ psi) at 21°C --- ### **Mechanical Properties (Typical at Room Temperature, Annealed Condition)** * **Tensile Strength:** ≥ 758 MPa (110 ksi) * **Yield Strength (0.2% Offset):** ≥ 345 MPa (50 ksi) * **Elongation:** ≥ 40% --- ### **Key Characteristics and Product Applications** #### **Key Characteristics:** 1. **Excellent Thermal Stability:** Highly resistant to embrittlement and intergranular corrosion after exposure to high temperatures (650-870°C), making it ideal for heat-treated components and welded structures. 2. **Good General Corrosion Resistance:** Resists a wide variety of chemical process environments, including organic acids, chlorine, and other halogens. 3. **Resistance to Stress Corrosion Cracking (SCC):** Performs well in chloride-containing environments where stress corrosion cracking is a concern. 4. **Good Fabricability:** It can be hot and cold worked using standard techniques and possesses good weldability. #### **Primary Applications:** Hastelloy C-4 is used in demanding chemical processing applications where high-temperature stability is paramount. * **Chemical Processing Industry (CPI):** * **Reactors and Vessels** for processes involving catalysts at high temperatures. * **Distillation Columns and Piping** in organic chloride service. * **Components in vinyl acetate and phthalic anhydride production.** * **Pollution Control:** * **Scrubbers and Ductwork** handling hot, aggressive gases. * **Acid Production:** * Equipment handling hydrochloric and sulfuric acids. --- ### **International Standards & Specifications** Hastelloy C-4 is covered by several key ASME and ASTM specifications for pressure equipment and general use. | Product Form | Standard / Specification | Designation | | :--- | :--- | :--- | | **General Material** | **UNS** | **N06455** | | **Bar, Billet, Forgings** | ASME SB-574 / ASTM B574 | UNS N06455 | | **Plate, Sheet, Strip** | ASME SB-575 / ASTM B575 | UNS N06455 | | **Seamless Pipe & Tube** | ASME SB-622 / ASTM B622 | UNS N06455 | | **Welded Tube** | ASME SB-619 / ASTM B619, ASME SB-626 / ASTM B626 | UNS N06455 | *Note: There is no "ASME SB-6119"; this is likely a typographical combination of SB-619 and SB-626, which cover welded tube.* | Welding Consumables | AWS A5.14 / AWS A5.11 | **ERNiCrMo-7** (wire) / **ENiCrMo-7** (electrode) | | :--- | :--- | :--- | **Note:** "Hastelloy" and "C-4" are registered trademarks of **Haynes International, Inc.** While newer alloys like C-276 and C-22 offer improved versatility, Hastelloy C-4 remains a specialized and highly effective solution for applications where thermal stability is the primary concern.

Packing of Standard Packing: Typical bulk packaging includes palletized plastic 5 gallon/25 kg. pails, fiber and steel drums to 1 ton super sacks in full container (FCL) or truck load (T/L) quantities. Research and sample quantities and hygroscopic, oxidizing or other air sensitive materials may be packaged under argon or vacuum. Solutions are packaged in polypropylene, plastic or glass jars up to palletized 3268 gallon liquid totes Special package is available on request.