Alloy 690, 2.4642, UNS N06690, Inconel 690 - nickel alloy

Alloy 690, 2.4642, UNS N06690, Inconel® 690 - nickel alloy according to ASTM B 166, EN 10302

Alloy 690, 2.4642, Inconel® 690 – description

Alloy 690 is an Ni-Cr-Fe alloy with the highest chromium content (~29%) among nickel alloys suitable for fabrication of pressure equipment. High Cr content gives it exceptional high-temperature oxidizing resistance. Notably, it has good nitridation and sulfidation resistance.

It has more Cr and less C than alloy 600 which makes it more resistant to stress-corrosion cracking in hot high-purity water.

Applications

The alloy is used in applications such as nuclear steam generators, coal gasification, and sulfuric, nitric/hydrofluoric acid processing.

Alloy 690, 2.4642, Inconel® 690 - physical and mechanical properties

Room temperature physical properties:

• Density: 8.2 g/cm³
• Specific heat capacity: 450 J/kg⋅K
• Thermal conductivity: 12 W/m⋅K
• Linear expansion coefficient: 14.3-17.3 μm/m⋅K
• Electrical resistivity: 1.15 µΩ⋅m
• Melting temperature: 1343-1377 °C

High-temperature coefficient of thermal expansion

• 20-200°C: 14.31 μm/m⋅K
• 20-300°C: 14.53 μm/m⋅K
• 20-400°C: 14.80 μm/m⋅K
• 20-500°C: 15.19 μm/m⋅K
• 20-600°C: 15.70 μm/m⋅K
• 20-700°C: 16.18 μm/m⋅K
• 20-800°C: 16.60 μm/m⋅K
• 20-900°C: 17.01 μm/m⋅K
• 20-1000°C: 17.41 μm/m⋅K
• 20-1000°C: 17.79 μm/m⋅K

High-temperature specific heat:

• 20°C: 450 J/kg⋅K
• 200°C: 497 J/kg⋅K
• 400°C: 551 J/kg⋅K
• 600°C: 604 J/kg⋅K
• 800°C: 658 J/kg⋅K
• 900°C: 684 J/kg⋅K
• 1000°C: 711 J/kg⋅K
• 1100°C: 738 J/kg⋅K

High-temperature thermal conductivity:

• 200°C: 15.4 W/m·K
• 400°C: 19.1 W/m·K
• 600°C: 22.9 W/m·K
• 800°C: 26.6 W/m·K
• 900°C: 28.5 W/m·K
• 1000°C: 30.1 W/m·K

High-temperature electrical resistivity:

• 20°C: 1.148 μΩ·m
• 200°C: 1.180 μΩ·m
• 400°C: 1.219 μΩ·m
• 600°C: 1.239 μΩ·m
• 800°C: 1.247 μΩ·m
• 900°C: 1.255 μΩ·m
• 1000°C: 1.265 μΩ·m

High-temperature Young's modulus (in the annealed condition):

• 20°C: 206.9 GPa
• 204°C: 196.5 GPa
• 316°C: 190.3 GPa
• 427°C: 183.4 GPa
• 760°C: 155.1 GPa
• 980°C: 136.5 GPa
• 1090°C: 125.5 GPa

Mechanical properties of annealed (+AT) 2.4642 long products according to EN 10302:

• Yield strength: >240 MPa
• Tensile strength: >590 MPa
• Elongation: >30%

High-temperature yield strength of 2.4642 long products, according to EN 10302:

• 100°C: >236 MPa
• 200°C: >228 MPa
• 300°C: >220 MPa
• 400°C: >216 MPa
• 500°C: >210 MPa
• 600°C: >200 MPa
• 700°C: >156 MPa
• 800°C: >120 MPa

Temperature stability - Inconel® 690 retains its mechanical properties despite prolonged exposure to high temperatures;

• Impact strength KV
  • No exposure: 190 J
  • 565°C, 1 000h: 156 J
  • 565°C, 4 000h: 171 J
  • 565°C, 12 000h: 164 J
  • 595°C, 1 000h: 195 J
  • 595°C, 4 000h: 170 J
  • 595°C, 13 428h: 170 J
  • 650°C, 1 000h: 198 J
  • 650°C, 4 000h: 179 J
  • 650°C, 12 000h: 172 J
  • 760°C, 1 000h: 214 J
  • 760°C, 4 000h: 201 J
  • 760°C, 12 000h: 184 J
• Elongation:
  • No exposure: 48 %
  • 565°C, 1 000h: 45 %
  • 565°C, 4 000h: 45 %
  • 565°C, 12 000h: 44 %
  • 595°C, 1 000h: 45 %
  • 595°C, 4 000h: 43 %
  • 595°C, 13 428h: 44 %
  • 650°C, 1 000h: 46 %
  • 650°C, 4 000h: 54 %
  • 650°C, 12 000h: 41 %
  • 760°C, 1 000h: 44 %
  • 760°C, 4 000h: 44 %
  • 760°C, 12 000h: 46 %

Corrosion behaviour

High-temperature water and dilute aqueous solutions - very good resistance to stress-corrosion cracking in such environments (nuclear steam generator). Superior to alloy 600, alloy X750 and alloy 718.

High-temperature nitridation - excellent resistance to HNO₃ and a good resistance to other nitriding agents.

Corrosion rates in nitric-plus-hydrofluoric acid solutions at 60 °C:

• 10% HNO₃ + 3% HF - 0.15mm/year
• 15% HNO₃ + 3% HF - 0.25mm/year
• 20% HNO₃ + 2% HF - 0.15mm/year

High-temperature sulfidation - excellent resistance thanks to the high chromium content.

Corrosion rates in oxidizing and reducing sulfidizing environments at 720 °C:

• 1,5% H₂ + 3%O₂ + 36,5% H₂ + 59% Ar: 2.3mm/year
• 1,5% H₂S + 98,5% H₂: 34.7mm/year

Weldability

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

Selection of welding consumables:

• ENiCrFe-3, ENiCrFe-7 (Electrode); ERNiCr-3, ERNiCrFe-7 (Filler metal)
• Joining with 0-9% Ni steel: ENiCrFe-2 (Electrode); ERNiCr-3 (Filler metal)
• Joining with copper: ENi-1 (Electrode); ERNi-1 (Filler metal)
• Joining with Nickel-copper: ENi-1 (Electrode); ERNi-1 (Filler metal)

Precaution is required to minimize copper dilution in the weld, because of the high chromium level of alloy 690. “Buttering” the copper or copper-nickel side of the joint with nickel weld metal prior to welding may be advisable.

Heat treatment, working and machining

Recommended working and heat treatment parameters:

• Heavy forging: 1230-1040 °C
• Light forging: >870°C °C
• Annealing: ~1040 °C

Machining - group C, meaning it's mechanical properties are similar to austenitic stainless steel. It's best machined in cold-drawn or cold-drawn and stress-relieved conditions.

Recommended turning parameters with high-speed steel:

• Roughing:
  • Feed: 0.25 mm/rev
  • Cutting speed: 15 m/min
• Finishing:
  • Feed: 0.13 mm/rev
  • Cutting speed: 18 m/min

We deliver this steel alloy as:

• Condenser and heat exchanger tubes according to ASTM B 163 / ASME SB163
• Seamless and welded pipes according to ASTM B 167 / ASME SB167. ASTM B 829 / ASME SB829, ISO 6207, EN 10302
• Plates, strips and sheets according to ASTM B 168 / ASME SB168, ISO 6208
• Forgings according to ASTM B 564 / ASME SB564

Replacements, equivalents and other designations:

Alloy 690, N06690, 0Cr30Ni60Fe10, H06690, NS3105, NS315, 2.4642, NW6690, NiCr29Fe, NCF690, ASTM B 163, ASTM B 166, ASTM B 167, ASTM B 168, ASTM B 516, ASTM B 834, ASME SB163, ASME SB166, ASME SB167, Inconel® 690, Sanicro® 690, Allvac 700, Haynes® 690, Nicrofer® 6030, DMV® 690, VDM® Alloy 690