Alloy 686, 2.4606, UNS N06686 - NICKEL ALLOY

Alloy 686, 2.4606, UNS N06686, Inconel® Alloy 686 - nickel alloy according to ASTM B366-17

Alloy 686, 2.4606, N06686, Inconel® alloy 686 – description

Alloy 686 (UNS N06686) is a single-phase, austenitic Ni-Cr-Mo superalloy with tungsten alloying addition. It resists highly aggresive oxidizing (thanks to high chromium) and reducing (nickel and molybdenum) environments. Thanks to very low iron and carbon content, as well as the blend of molybdenum and tungsten, it offers optimum resistance to localized corrosion such as pitting and crevice. Low carbon maintains corrosion-resistance in the heat-affected zones of welded joints.

Approved by NACE MR0175 for oil and gas use, approved by VdTÜV for use at temperatures up to 400°C in Werkstoffblatt 515/12.97. Allowable design stresses for ASME Section VIII, Division 1 construction for service up to 800°F are defined in ASME Code Case 2198 and Table 1B of ASME Section II, Part D. For ASME fabrication, alloy 686 is classified as a P-No.43 material.

Applications

Used in chemical process, pulp manufacture, paper manufacture, pollution control, and waste management applications.

Physical and Tensile Properties

Room temperature physical properties:

• Density: 8.73 g/cm³
• Liquidus Temperature: 1380 °C
• Solidus Temperature: 1338 °C
• Electrical Resistivity: 1.237 μΩ·m

High-Temperature Coefficient of Thermal Expansion, from 20°C to:

• 100°C: 11.97 μm/m⋅K
• 200°C: 12.22 μm/m⋅K
• 300°C: 12.56 μm/m⋅K
• 400°C: 12.87 μm/m⋅K
• 500°C: 13.01 μm/m⋅K
• 600°C: 13.18 μm/m⋅K

Specific Heat Capacity:

• -15°C: 364 J/kg⋅K
• 20°C: 373 J/kg⋅K
• 100°C: 389 J/kg⋅K
• 200°C: 410 J/kg⋅K
• 300°C: 431 J/kg⋅K
• 400°C: 456 J/kg⋅K
• 500°C: 477 J/kg⋅K
• 600°C: 498 J/kg⋅K
• 700°C: 519 J/kg⋅K

Electrical Resistivity:

• 20°C: 1.237 μΩ·m
• 100°C: 1.246 μΩ·m
• 200°C: 1.257 μΩ·m
• 300°C: 1.263 μΩ·m
• 400°C: 1.272 μΩ·m
• 500°C: 1.289 μΩ·m
• 600°C: 1.295 μΩ·m
• 700°C: 1.279 μΩ·m

Young's Modulus:

• 20°C: 207 GPa
• 100°C: 205 GPa
• 200°C: 197 GPa
• 300°C: 193 GPa
• 400°C: 185 GPa
• 500°C: 183 GPa
• 600°C: 173 GPa
• 700°C: 165 GPa

Shear Modulus:

• 20°C: 77 GPa
• 100°C: 75 GPa
• 200°C: 72 GPa
• 300°C: 70 GPa
• 400°C: 69 GPa
• 500°C: 67 GPa
• 600°C: 65 GPa
• 700°C: 61 GPa

Poisson's Ratio:

• 20°C: 0.34
• 100°C: 0.37
• 200°C: 0.37
• 300°C: 0.38
• 400°C: 0.34
• 500°C: 0.37
• 600°C: 0.33
• 700°C: 0.35

Thermal Conductivity:

• 20°C: 9.8 W/m · K
• 100°C: 11 W/m · K
• 200°C: 12.8 W/m · K
• 300°C: 14.8 W/m · K
• 400°C: 16.6 W/m · K
• 500°C: 18.6 W/m · K
• 600°C: 21.4 W/m · K
• 700°C: 23.5 W/m · K
• 800°C: 25.3 W/m · K
• 900°C: 26.4 W/m · K
• 1000°C: 29.6 W/m · K
• 1100°C: 31.6 W/m · K
• 1150°C: 32.6 W/m · K

Thermal Stability - room temperature impact strength of Inconel alloy 686 after 100 hours of exposure to high temperature:

• as annealed: 405 J
• 540°C: 400 J
• 650°C: 401 J
• 760°C: 25.1 J
• 870°C: 8.1 J
• 980°C: 2.7 J

Thermal Stability - low temperature (-196°C) impact strength of Inconel alloy 686 after 100 hours of exposure to high temperature:

• as annealed: 404 J
• 540°C: 405 J
• 650°C: 403 J
• 760°C: 12.2 J
• 870°C: 3.4 J
• 980°C: 2.7 J

High-Temperature Tensile Properties of Inconel 686 according to the producer:

• 20°C:
  • Yield strength: 396 MPa
  • Tensile strength: 740 MPa
  • Elongation: 60 %
• 93°C:
  • Yield strength: 323 MPa
  • Tensile strength: 691 MPa
  • Elongation: 69 %
• 204°C:
  • Yield strength: 290 MPa
  • Tensile strength: 635 MPa
  • Elongation: 67 %
• 316°C:
  • Yield strength: 288 MPa
  • Tensile strength: 602 MPa
  • Elongation: 60 %
• 427°C:
  • Yield strength: 224 MPa
  • Tensile strength: 570 MPa
  • Elongation: 69 %
• 540­°C:
  • Yield strength: 261 MPa
  • Tensile strength: 545 MPa
  • Elongation: 61 %

Mechanical properties of Inconel 686 plates and sheets:

• Thickness: 12.7 mm
  • Yield strength: 364 MPa
  • Tensile strength: 722 MPa
  • Elongation: 71 %
• Thickness: 6.35 mm
  • Yield strength: 399 MPa
  • Tensile strength: 733 MPa
  • Elongation: 68 %
• Thickness: 3.18 mm
  • Yield strength: 421 MPa
  • Tensile strength: 803 MPa
  • Elongation: 59 %
• Thickness: 1.57 mm
  • Yield strength: 408 MPa
  • Tensile strength: 848 MPa
  • Elongation: 59 %

Mechanical properties of Inconel 686 rods, 38 mm in diameter, according to the producer:

• Yield strength: 359 MPa
• Tensile strength: 810 MPa
• Elongation: 56 %

Mechanical properties of alloy 2.4606 sheets and plates, according to DIN 17750 and DIN 17752; temper designation F69:

• Yield strength: >310 MPa
• Tensile strength: >690 MPa
• Elongation: >45 %
• Hardness: <240 HBW

Corrosion Resistance

Very good resistance to oxidizing and non-oxidizing environments.

Localized corrosion – extremely high resistance to pitting and crevice corrosion. The PREN index, used to compare the pitting resistance of alloys, is 51, a very high score. The Critical Crevice Temperature and Critical Pitting Temperature in an acidified 6% ferric chloride solution (ASTM G48 C&D) is >85°C.

Acids and halides – The alloy is successfully used in contact with acids with a high halide content. It withstands chloride levels exceeding 100,000 ppm. It also shows good resistance to acid mixtures with a pH below 1. Corrosion rates in various acid environments:

• Sulphuric acid (H₂SO₄) 80%, at 80°C: 0.1 mm/year
• Sulphuric acid (H₂SO₄) 10% + HCL 2%, boiling: 3.35 mm/year
• Sulphuric acid (H₂SO₄) 10% + HCL 5%, at 80°C: 0.86 mm/year
• Hydrogen chloride (HCL) 0.2%, boiling: <0.025 mm/year
• Hydrogen chloride (HCL) 1%, boiling: 0.05 mm/year
• Hydrogen chloride (HCL) 2%, boiling: 0.15 mm/year
• Hydrogen chloride (HCL) 5%, at 70°C: 0.25 mm/year
• Hydrogen chloride (HCL) 5%, at 50°C: 0.05 mm/year
• Phosphoric acid (H₃PO₄) 85%, boiling: 0.41 mm/year
• Phosphoric acid (H₃PO₄) 85%, at 0,9°C: <0.025 mm/year

Effect of Heat Treatment on IGA Resistance(ASTM G28 B; 24-hour test):

• as annealed: 0,3 mm/year
• 760°C: 0,33 mm/year
• 870°C: 0,43 mm/year
• 980°C: 0,69 mm/year

Corrosion rates in simulated FGD outlet-duct environments:

• Sulphuric acid (H₂SO₄) 60% + HCL 0.5% + HF 0.1% + HNO₃ 0.1%, at 85°C: 0.36 mm/year
• Sulphuric acid (H₂SO₄) 60% + HCL 2.5% + HF 0.2% + fly ash 0.1%, at 80°C: 0.58 mm/year
• Sulphuric acid (H₂SO₄) 70% + HCL 2.5% + HF 0.2%, at 105°C: 6.96 mm/year

Seawater - Excellent resistance to all types of general and localized corrosion, both for products in the annealed condition and those hardened by cold working (e.g., for high strength bolting).

Heat Treatment, Working and Machining

Standard recommended working and heat treatment parameters:

• Hot forming: 1230-1090 °C
• Light hot forming: >870 °C
• Annealing: 1180-1200°C; water quench

Weldability

Readility weldable without the need for post-weld heat treatment. Use alloy 686 filler metal (AWS A5.14 ERNiCrMo-14, INCO-WELD® 686 CPT filler metal) or, alternatively, coated electrodes ENiCrMo-3 or filler metals ERNiCrMo-4 through -10.

Alloy 686 Filler metal - Alloy 686 filler metal is available (AWS A5.14 ERNiCrMo-14, INCO-WELD® 686 CPT filler metal). It is ideal for joining nickel alloys (e.g., alloy 686, alloy C-276, alloy 22) as well as duplex, super-duplex, and super-austenitic stainless steels. It is also highly effective for welding dissimilar alloys. Welds made with alloy 686 usually have superior resistance to pitting and crevice corrosion compared to the base metal.

Weld alloy 686 using alloy 686 filler wire, but coated electrodes ENiCrMo-3 and ERNiCrMo filler metals numbered 4 through 10 can also be used.

We deliver this steel alloy as:

• Rod, bar, wire, forging, sheet, plate according to NACE RP0294
• Rod, bar, wire, forging according to ASTM B 462 / ASME SB-461; ASTM B 564 / ASME SB-564; ASTM B 574 / ASME SB 574; DIN 17752, DIN 17753, DIN 17754
• Sheets and plates according to ASTM B 575 / ASME SB-575; ASTM B 906 / ASME SB-906; DIN 17750
• Pipes according to ASTM B 163 / ASME SB 163; ASTM B 619 / ASME SB-619; ASTM B 622 / ASME SB-622; STM B 626 / ASME SB 626; ASTM B 751 / ASME SB 751; ASTM B 775 / ASME SB 775; ASTM B 829 / ASME SB 829; DIN 17751
• Filler metal ERNiCrMo-14
• Coated electrodes ENiCrMo-14
• Fittings according to ASTM F 467; F 467M; F 468; F 468M; SAE/AMS J2295; J2271; J2655; J2280; J2484; J2485