Alloy C4, UNS N06455, 2.4610, Hastelloy® C-4 - nickel alloy

Alloy C4, UNS N06455, 2.4610, Hastelloy® C-4 - nickel alloy according to DIN 17744:2019 i ASME SB366-21

Alloy C4, 2.4610, Hastelloy® C-4 – description

Alloy C4 is a tungsten-free, low-carbon, low-silicon ternary alloy of nickel, chromium, and molybdenum with addition of titanium to stabilize residual carbon. It has an outstanding high-temperature stability, excellent resistance to aggresive aqueous environments and good weldability. It can be seen as a more stable and better weldable variant of Alloy C-276.

Thermal stability and weldability - Alloy C4 displays good ductility and corrosion resistance after long-time aging at 650 to 1040°C. It resists formation of grain-boundary precipitates in weld heat-affected zones, and is apt for most chemical process applications without any additional post-welding heat treatment. It has excellent resistance to stress-corrosion cracking and to oxidizing atmospheres up to 1040°C.

Applications

Alloy C-4 is mainly used in chemical processing.

Alloy C4, Hastelloy® C-4 - physical and mechanical properties

Room temperature physical properties:

• Density: 8.64 g/cm³

High-temperature Coefficient of thermal expansion, from 20°C to:

• 93°C: 10.8 μm/m⋅K
• 205°C: 11.9 μm/m⋅K
• 315°C: 12.6 μm/m⋅K
• 425°C: 13.0 μm/m⋅K
• 540°C: 13.3 μm/m⋅K
• 650°C: 13.5 μm/m⋅K
• 760°C: 14.4 μm/m⋅K
• 870°C: 14.9 μm/m⋅K
• 980°C: 15.7 μm/m⋅K

High-temperature Specific heat capacity:

• 0°C: 406 J/kg⋅K
• 100°C: 426 J/kg⋅K
• 200°C: 448 J/kg⋅K
• 300°C: 465 J/kg⋅K
• 400°C: 477 J/kg⋅K
• 500°C: 490 J/kg⋅K
• 600°C: 502 J/kg⋅K

High-temperature Thermal diffusivity:

• 20°C: 2.8 10^–6⋅m²/s
• 100°C: 3.1 10^–6⋅m²/s
• 200°C: 3.3 10^–6⋅m²/s
• 300°C: 3.7 10^–6⋅m²/s
• 400°C: 4.0 10^–6⋅m²/s
• 500°C: 4.3 10^–6⋅m²/s
• 600°C: 4.7 10^–6⋅m²/s

High-temperature Thermal conductivity:

• 20°C: 10.0 W/m · K
• 100°C: 11.4 W/m · K
• 200°C: 13.2 W/m · K
• 300°C: 14.9 W/m · K
• 400°C: 16.6 W/m · K
• 500°C: 18.4 W/m · K
• 600°C: 20.4 W/m · K

High-temperature Electrical resistivity:

• 20°C: 1.25 μΩ·m
• 200°C: 1.26 μΩ·m
• 400°C: 1.28 μΩ·m
• 600°C: 1.32 μΩ·m

High-temperature Elastic modulus of 12.7 mm thick Hastelloy® C-4 plate heat treated at 1065°C and quenched:

• 93°C: 10.0 GPa
• 205°C: 11.4 GPa
• 315°C: 13.2 GPa
• 425°C: 14.9 GPa
• 540°C: 16.6 GPa
• 650°C: 18.4 GPa
• 760°C: 20.4 GPa
• 870°C: 18.4 GPa
• 980°C: 20.4 GPa

Tensile properties of Alloy C4 rods and bars after tempering designated as F69 according to DIN 17752:2019:

• Yield strength: >280 MPa
• Tensile strength: >690 MPa
• Elongation: >35 %
• Hardness HBW: <240

Tensile properties of Alloy C4 plates and sheets after tempering designated as F69 according to DIN 17752:2019:

• D: <5 mm
  • Yield strength: >305 MPa
  • Tensile strength: >690 MPa
  • Elongation: >40 %
  • Hardness HBW: <240
• D: <5 mm
  • Yield strength: >280 MPa
  • Tensile strength: >690 MPa
  • Elongation: >40 %
  • Hardness HBW: <240

Corrosion behaviour

Alloy C-4 has very good general corrosion resistance and high resistance to pitting.

High-temperature oxidation - very good resistance up to 1040°C.

Halogenation - very good resistance. C-4 is one of the alloys most resistant to hydrochloric acid (HCl), which is evident from metal loss experienced after exposition to HCl at elevated temperatures:

• HCl 300h; 400°C: 0.55 mg/cm²
• HCl 1000h; 400°C: 1.12 mg/cm²
• HCl 100h; 500°C: 2.09 mg/cm²
• HCl 300h; 500°C: 3.36 mg/cm²
• HCl 1000h; 500°C: 7.24 mg/cm²
• HCl 100h; 600°C: 7.31 mg/cm²
• HCl 300h; 600°C: 19.14 mg/cm²
• HCl 96h; 700°C: 34.9 mg/cm²

Pitting corrosion in chloride environments - good resistance. The critical pitting temperature in 6% FeCl₃ for 24 h period is 37.5°C. For 20,4% solution of MgCl₂, the temperature is 230°C.

Corrosion rate in specific environments:

• Acetic acid (CH₃COOH) 99%, boiling: 0 mm/year;
• Ferric chloride (FeCl₃) 10%, boiling: 3.5 mm/year;
• Formic acid (CH₂O₂) 88%, boiling: 0.05 mm/year;
• Hydrochloric acid (HCl) 1%, boiling: 0.625 mm/year;
• ^ 1,5%, boiling: 1.6 mm/year;
• ^ 2%°C, at 90°C: 0.775 mm/year;
• ^ 2%, boiling: 2.05 mm/year;
• ^ 2,5%°C, at 90°C: 0.85 mm/year;
• ^ 2,5%, boiling: 1.1 mm/year;
• ^ 10%, boiling: 5.7 mm/year;
• ^ 5% + 42g/L Fe₂(SO₄)₃°C, at 66°C: 0.075 mm/year;
• ^ 5% + 2% HF°C, at 70°C: 0.85 mm/year;
• Hydrofluoric acid (HF) 2%°C, at 70°C: 0.425 mm/year;
• ^ 5%°C, at 70°C: 0.375 mm/year;
• Nitric acid (HNO₃) 10%, boiling: 0.175 mm/year;
• ^ 65%, boiling: 5.425 mm/year;
• ^ 5% + 6% HF°C, at 60°C: 5.1 mm/year;
• ^ 5% + 25% H₂SO₄ + 4% NaCl, boiling: 2.425 mm/year;
• ^ 5% + 1% HCl, boiling: 0.275 mm/year;
• ^ 5% + 2.5% HCl, boiling: 0.65 mm/year;
• ^ 9% + 15.8% HCl°C, at 52°C: 2.85 mm/year;
• Sulfuric acid (H₂SO₄) 2%°C, at 66°C: 0 mm/year;
• ^ 2%, boiling: 0.15 mm/year;
• ^ 5%°C, at 79°C: 0.025 mm/year;
• ^ 5%, boiling: 0.4 mm/year;
• ^ 10%, boiling: 0.625 mm/year;
• ^ 20%°C, at 66°C: 0.0125 mm/year;
• ^ 20%°C, at 79°C: 0.05 mm/year;
• ^ 20%, boiling: 0.9 mm/year;
• ^ 30%°C, at 66°C: 0.0125 mm/year;
• ^ 30%°C, at 79°C: 0.075 mm/year;
• ^ 30%, boiling: 1.825 mm/year;
• ^ 40%°C, at 38°C: 0.0125 mm/year;
• ^ 40%°C, at 66°C: 0.225 mm/year;
• ^ 40%°C, at 79°C: 0.375 mm/year;
• ^ 50%°C, at 38°C: 0.0125 mm/year;
• ^ 50%°C, at 66°C: 0.325 mm/year;
• ^ 50%°C, at 79°C: 0.625 mm/year;
• ^ 60%°C, at 38°C: 0.025 mm/year;
• ^ 70%°C, at 38°C: 0.05 mm/year;
• ^ 80%°C, at 38°C: 0.0125 mm/year;
• ^ 5% + 0.1% HCl, boiling: 1.225 mm/year;
• ^ 5% + 0.5% HCl, boiling: 2.275 mm/year;
• ^ 10% + 1% HCl°C, at 70°C: 0.6 mm/year;
• ^ 10% + 1% HCl°C, at 90°C: 1.65 mm/year;
• ^ 10% + 1% HCl, boiling: 4.8 mm/year;
• ^ 10% + 2% HF, boiling: 0.65 mm/year;
• ^ 25% + 200 ppm Cl^-°C, at 70°C: 0.925 mm/year;
• ^ 25% + 200 ppm Cl^-, boiling: 4.55 mm/year;
• ^ 12% + 1.2% HCl + 1% FeCl₃ + 1% CuCl₂, boiling: 20.925 mm/year;
• ^ 23% + 1.2% HCl + 1% FeCl₃ + 1% CuCl₂, boiling: 53.875 mm/year;
• ^ 50% + 42g/L Fe₂(SO₄)₃ (ASTM G 28A), boiling: 3.575 mm/year;

Weldability

Alloy C-4 resists the formation of grain-boundary precipitates in weld heat-affected zones and is suitable for most chemical process applications in the as-welded condition.

Weldability group 43 (ISO 15608), brazing P-number 111 (ASME section IX).

Selection of welding consumables for N06625:

• Coated electrodes: ENiCrMo-7
• Filler metal: ERNiCrMo-7

Heat treatment, working and machining

Recommended working and heat treatment parameters:

• Forging: 1177-954 °C
• Soft annealing: 1065±14 °C; 30 min; WQ

Forging - alloy can be hot forged within a rather narrow temperature range, starting at 1177°C and finishing at 954°C. Moderate reductions and frequent re-heating are recommended for optimal results. The alloy is sensitive to strain.

Cold working does not reduce the general corrosion resistance, but it can affect resistance to stress corrosion cracking. Post-working annealing is important for best corrosion performance.

Annealing involves heating to 1066°C and water quenching. A hold time at the annealing temperature of 10 to 30 minutes is recommended, with thicker structures requiring the full 30 minutes. Annealing is essential after hot forming operations and any cold forming that results in an outer fiber elongation of 7% or more.

Postweld heat treatment for caustic applications - Heat the material to 705 °C and maintain this temperature for at least 0.5 hours per 25 mm of thickness. Determine the heating and cooling rates based on the shape of the part. For complex shapes with nonuniform thicknesses, use heating and cooling rates of 111 °C per hour. Shapes with uniform thicknesses can employ faster heating and air cooling.

We deliver this steel alloy as:

• Rod, bar, wire, forging according to ASMT B 574 / ASME SB-574, DIN 17752
• Plates, strips and sheets according to ASTM B 575 / ASME SB-575, DIN 17750
• Welded pipes according to ASTM B 617 / ASME SB-619
• Seamless pipes according to ASTM B 622 / ASME SB-622
• Welded fittings according to ASTM B 366 / ASME SB-366

Replacements, equivalents and other designations:

Alloy C4, UNS N06455, H06455, NS3305, NS335, 2.4610, NiMo16Cr16Ti, NA 45 BS 2901, NW6455, NiMo16Cr17Ti, Hastelloy® C-4, ASTM A 494, ASTM A 494 Grade CW2M, ASTM A 990 Grade CW-2M, ASTM B 366 (CRHC4), ASTM B 366 (WPHC4), ASTM B 574, ASTM B 575, ASTM B 619, ASTM B622, ASME SB-494, ASME SB-990, ASME SB-366 (CRHC4), ASME SB-366 (WPHC4), ASME SB-574, ASME SB-575, ASME SB-619, ASME SB-622, Junkeralloy C4C, Nicrofer® 6616 hMo, Nistelle C-4, VDM® Alloy C-4, Coralloy C-4, ERNiCrMo-7