Alloy B3, 2.4600, UNS N10675, Hastelloy® B3 - nickel alloy

Alloy B3, 2.4600, UNS N10675, Hastelloy® B-3 - nickel alloy according to ASTM B366, DIN 17750

Alloy B3, 2.4600, Hastelloy® B3 – description

Alloy B3 is a Ni-Mo alloy, a third generation in B-type family of alloys. A quick rundown of this family history gives a good understanding of its main strong points. Alloy B has been used since about 1929 in applications where excellent resistance to nonoxidizing chemicals was needed, but it has suffered from one significant drawback: weld decay. Alloy B-2 addressed this issue and its welds are much more resistant to corrosion, but it becomes very brittle when subjected to the temperature ranging 540-815°C. Alloy B3 offers significantly better thermal stability, fabricability, and stress-corrosion cracking resistance than alloy B-2, while providing the same excellent resistance to hydrochloric acid and other strongly reducing agents.

Selected standards describing the alloy:

• ASTM B 333, ASME SB-333 - Plates, strips and sheets
• ASTM B 335, ASME SB-335 - Bars
• ASTM B 626, ASME SB-626 - Welded pipes
• ASTM B 622, ASME SB-622 - Seamless pipes
• ASTM B 366, ASME SB-366 - Welded fittings
• DIN 17750 - Properties of plates, strips and sheets
• DIN 17744 - Chemical composition

Applications

Alloy B-3 is used mostly in chemical processing for equipment handling hydrochloric acid (all concentrations and temperatures), sulfuric acid, acetic acid and phosphoric acid.

Alloy B3, Hastelloy® B-3 - physical and mechanical properties

Room temperature physical and mechanical properties of Hastelloy® B3, according to the producer:

• Density: 9.22 g/cm³
• Electrical resistivity: 1.37 μΩ⋅m
• Thermal diffusivity: 3.0 ⋅ 10^-6⋅m²/s
• Coefficient of thermal expansion: 10.6 μm/m⋅K
• Melting temperature: 1370-1418 °C
• Elastic modulus: 216 GPa

Mechanical properties of 2.4600 according to DIN 17750:

• Yield strength: >340 MPa
• Tensile strength: >750 MPa
• Elongation: >40%
• Hardness HBW: <240

Tensile properties of Hastelloy® B-33.2 mm thick sheets, bright annealed:

• Room temperature
  • Tensile strength: 860 MPa
  • Yield strength: 420 MPa
  • Elongation: 53.4 %
• 100°C:
  • Tensile strength: 830 MPa
  • Yield strength: 380 MPa
  • Elongation: 56.9 %
• 200°C:
  • Tensile strength: 760 MPa
  • Yield strength: 325 MPa
  • Elongation: 59.7 %
• 315°C:
  • Tensile strength: 720 MPa
  • Yield strength: 300 MPa
  • Elongation: 63.4 %
• 425°C:
  • Tensile strength: 705 MPa
  • Yield strength: 290 MPa
  • Elongation: 62.0 %
• 540°C:
  • Tensile strength: 675 MPa
  • Yield strength: 270 MPa
  • Elongation: 59.0 %
• 650°C:
  • Tensile strength: 715 MPa
  • Yield strength: 315 MPa
  • Elongation: 55.8 %

Tensile properties of Hastelloy® B-36.4 mm thick plates, solution treated:

• Room temperature
  • Tensile strength: 885 MPa
  • Yield strength: 400 MPa
  • Elongation: 57.8 %
• 100°C:
  • Tensile strength: 845 MPa
  • Yield strength: 375 MPa
  • Elongation: 58.2 %
• 200°C:
  • Tensile strength: 795 MPa
  • Yield strength: 330 MPa
  • Elongation: 60.9 %
• 315°C:
  • Tensile strength: 765 MPa
  • Yield strength: 305 MPa
  • Elongation: 61.6 %
• 425°C:
  • Tensile strength: 745 MPa
  • Yield strength: 285 MPa
  • Elongation: 61.7 %
• 540°C:
  • Tensile strength: 730 MPa
  • Yield strength: 275 MPa
  • Elongation: 61.7 %
• 650°C:
  • Tensile strength: 735 MPa
  • Yield strength: 290 MPa
  • Elongation: 64.6 %

Temperature stability of Hastelloy® B-3 alloy - elongation values as a function of exposure time to the given temperature:

• T. duration 1000 h, 425°C: 57.2 %
• T. duration 1000 h, 480°C: 50 %
• T. duration 1000 h, 540°C: 48.4 %
• T. duration 1000 h, 595°C: 38.8 %
• T. duration 8000 h, 425°C: 57.4 %
• T. duration 8000 h, 480°C: 48.9 %
• T. duration 8000 h, 540°C: 47.1 %
• T. duration 8000 h, 595°C: 28.7 %
• T. duration 16 000 h, 425°C: 57.6 %
• T. duration 16 000 h, 480°C: 48.8 %
• T. duration 16 000 h, 540°C: 43.7 %
• T. duration 16 000 h, 595°C: 25.3 %

Corrosion behaviour

Of all nickel-based alloys, alloy B-3, together with alloy B-2, show the highest resistance to hydrochloric acid HCl and extremely high resistance to other reducing compounds, while alloy B-3 has better resistance to stress-corrosion cracking and thermal stability. Please note that iron and copper salts greatly accelerate corrosion and can form when hydrochloric acid comes into contact with iron or copper, hence alloy B3 should not be used where iron or copper comes into contact with hydrochloric acid.

Average corrosion rates in boiling solutions:

• Acetic acid CH₃COOH, 50%: 0.005 mm/year
• Formic acid CH₂O₂, 40%: 0.013 mm/year
• Phosphoric acid H₃PO₄, 55%: 0.076 mm/year
• Sulfuric acid H₂SO₄, 50%: 0.043 mm/year
• Hydrochloric acid HCl, 20%: 0.305 mm/year

Stress-corrosion cracking - very good resistance. After 1008 hours of testing in a boiling 45% magnesium chloride solution (according to ASTM G 36), alloy B-3 showed no cracking.

Weldability

Weldability group 44 (according to ISO 15608), brazing P-number 112 (ASME section IX). Filler metal: ERNiMo-7

If the cold work is greater than 7%, solution annealing should be performed before welding, otherwise the alloy is susceptible to cracking.

Heat treatment, working and machining

Alloy can be hot forged and cold worked. Typical heat treatment:

• Forging: 1230-980°C
• Solutioning: 1060°C; water or rapid air cooling

Replacements, equivalents and other designations:

Alloy B3, Ni1067, NiMo30Cr, 2.4600, Hastelloy® B-3, Hastelloy® B3, AMS 5396, ASTM B 333, ASTM B 335, ASTM B 366, ASTM B 462, ASTM B 564, ASTM B 619, ASTM B 622, ASTM B 626, Hastelloy® B SAE, UNS N10675, VDM Alloy N10675, NiMo29Cr