Alloy 925, UNS N09925, Incoloy® 925 - nickel alloy

Alloy 925, UNS N09925, Incoloy® 925 - nickel alloy according to ASTM B637, API 6ACRA

Alloy 925, Incoloy® 925 – description

Alloy 925 (N09925) is a high-strength, corrosion resistant, age-hardenable Ni-Cr-Fe alloy with alloying additions of molybdenum, copper, titanium and aluminum. It can be seen as an improved version of alloy 825 with comparable corrosion resistance but higher strength obtained by age hardening.

Applications

Alloy 925 is used mainly in oil and gas production for down-hole and surface gaswell components including tubular products, valves, hangers, landing nipples, tool joints, fasteners, packers and piping. It is also used in the marine industry.

Physical and Tensile Properties

Room temperature physical properties:

• Density: 8.08 g/cm³
• Melting Temperature: 1311-1366 °C
• Magnetic Permeability: <1.001
• Electrical Resistivity: 1.17 μΩ·m

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

• 100°C: 13.2 μm/m⋅K
• 200°C: 14.2 μm/m⋅K
• 300°C: 14.7 μm/m⋅K
• 400°C: 15.0 μm/m⋅K
• 500°C: 15.3 μm/m⋅K
• 600°C: 15.7 μm/m⋅K
• 700°C: 16.3 μm/m⋅K
• 800°C: 17.2 μm/m⋅K

Thermal Conductivity:

• 20°C: 12.0 W/m · K
• 100°C: 12.9 W/m · K
• 200°C: 14.3 W/m · K
• 300°C: 15.9 W/m · K
• 400°C: 17.4 W/m · K
• 500°C: 19.3 W/m · K
• 600°C: 22.2 W/m · K
• 700°C: 24.0 W/m · K
• 800°C: 28.2 W/m · K
• 900°C: 27.7 W/m · K
• 1000°C: 24.6 W/m · K
• 1100°C: 26.0 W/m · K
• 1150°C: 26.9 W/m · K

Specific Heat Capacity:

• 20°C: 435 J/kg⋅K
• 100°C: 456 J/kg⋅K
• 200°C: 486 J/kg⋅K
• 300°C: 507 J/kg⋅K
• 400°C: 532 J/kg⋅K
• 500°C: 561 J/kg⋅K
• 600°C: 586 J/kg⋅K
• 700°C: 611 J/kg⋅K
• 800°C: 641 J/kg⋅K
• 900°C: 666 J/kg⋅K

Poisson's ratio:

• 20°C: 0.293
• 40°C: 0.299
• 100°C: 0.308
• 150°C: 0.316
• 200°C: 0.315
• 260°C: 0.317
• 315°C: 0.319
• 370°C: 0.319
• 427°C: 0.323
• 482°C: 0.323
• 540°C: 0.324
• 600°C: 0.326
• 650°C: 0.330
• 700°C: 0.334
• 760°C: 0.338
• 815°C: 0.335
• 870°C: 0.330
• 925°C: 0.326

Young's Modulus:

• 20°C: 199 GPa
• 40°C: 199 GPa
• 100°C: 195 GPa
• 150°C: 192 GPa
• 200°C: 188 GPa
• 260°C: 185 GPa
• 315°C: 182 GPa
• 370°C: 178 GPa
• 427°C: 175 GPa
• 482°C: 172 GPa
• 540°C: 168 GPa
• 600°C: 164 GPa
• 650°C: 160 GPa
• 700°C: 155 GPa
• 760°C: 150 GPa
• 815°C: 145 GPa
• 870°C: 139 GPa
• 925°C: 132 GPa

Shear Modulus:

• 20°C: 77 GPa
• 40°C: 76 GPa
• 100°C: 75 GPa
• 150°C: 73 GPa
• 200°C: 72 GPa
• 260°C: 70 GPa
• 315°C: 69 GPa
• 370°C: 68 GPa
• 427°C: 66 GPa
• 482°C: 65 GPa
• 540°C: 64 GPa
• 600°C: 62 GPa
• 650°C: 60 GPa
• 700°C: 58 GPa
• 760°C: 56 GPa
• 815°C: 54 GPa
• 870°C: 52 GPa
• 925°C: 50 GPa

Mechanical properties of cold-worked and aged Incoloy® alloy 925 bars, according to the Special Metals:

• Yield strength: >724 MPa
• Tensile strength: >965 MPa
• Elongation: >18%
• Reduction of area: >25 %
• Hardness: 26-38 HRC
• Impact energy KV -60°C: 47,4J

Mechanical properties of hot-worked and aged Incoloy® alloy 925 bars, according to the Special Metals:

• Yield strength: >758 MPa
• Tensile strength: >965 MPa
• Elongation: >18%
• Reduction of area: >25 %
• Hardness: 26-38 HRC
• Impact energy KV -60°C: 47,4J

Alloy 925 retains much of its strength at temperatures up to 650°C.

Maximum allowed hardness according to NACE MR0175/ISO 15156-2015:

• Cold worked: 35 HRC
• Solution annealed: 35 HRC
• Solution annealed and aged: 38 HRC
• Cold-worked and aged: 40 HRC
• Hot-finished and aged: 40 HRC

Hot finish parameters are described in the "Heat treatment" section.

Corrosion Resistance

Alloy 925 resists wide range of corrosive environments (sour gas, crude oil) and is very useful Gas&Oil industry. Below tests were conducted according to NACE guidelines.

Sulfide stress cracking in a simulated sour well environment - alloy 925 shows no cracks after 30-42 days of testing in 5% sodium chloride (NaCl) plus 0,5% acetic acid (CH₃COOH) saturated with hydrogen sulphide (H₂S), at room temperature, when coupled to carbon steel, and at 100% yield strength.

Stress-corrosion cracking in a simulated sour well environment - good resistance. Comparison of C-ring autoclave test results:

• 15 days at 100% of yield strength in 15% sodium chloride (NaCl) + 1380 kPa hydrogen sulphide (H₂S) + 690 kPa carbon dioxide (CO₂) + 1g/l sulfur at 232°C did produced cracks.
• 15 days at 100% of yield strength in 25% sodium chloride (NaCl) + 1380 kPa hydrogen sulphide (H₂S) + 690 kPa carbon dioxide (CO₂) + 1g/l sulfur at 204°C did produced cracks.
• 42 days at 100% of yield strength in 25% sodium chloride (NaCl) saturated with hydrogen sulphide (H₂S) + 6900 gas phase of 1% H₂S, 50% CO₂, 49% N₂ at 204°C did NOT produced cracks.

Marine applications - very good resistance.

Corrosion rates in various acid environments:

• Hydrochloric acid (HCl) 0,2%, boiling: <0.01 mm/year
• 1%°C, at 70°C°C: 0.28 mm/year
• Sulfuric acid (H₂SO₄) 10%°C, at 70°C°C: 0.05 mm/year
• Phosphoric acid (H₃PO₄) 85%°C, at 90°C°C: <0.03 mm/year
• 85%, boiling: 1.19 mm/year
• Acetic acid (CH₃COOH) 80%, boiling: <0.01 mm/year

Weldability

Very good weldability, preferably using GTAW or GMAW. Selection of welding consumables:

• ERNiCrMo-17 / SG-NiCr23Mo16Cu / 725NDUR® (Filler metal)

For best thermal stability, apply annealing pre-weld and annealing + aging after welding.

Heat Treatment, Working and Machining

Recommended hot work and heat treatment parameters:

• Forging: 1175-870°C
• Solution-treatment: 980-1040°C 0.5-4h; for sizes up to 25mm WQ or AC, for sizes above 25mm WQ.
• Age-hardening: 730-750°C for 8h; Furnace cooling: 55°C/h for 2h; Age-hardening: 610-630°C for 8h; AC or WQ

Note: for maximum corrosion resistance and mechanical properties after aging, final hot working should be done at 980-870°C.

Machining - the alloy is relatively easily machined in the solutioned condition. Difficult to machine in age-hardened condition. Roughing in annealed condition and then finishing in aged condition is recommended. Typical machining data:

• Roughing in annealed condition (carbide):
  • Feed: 0.5 mm/rev
  • Cutting speed: 53-76 m/min
  • Depth of cut: 6.4 mm
  • Tool material: C-6
• Roughing in annealed condition (high speed steel):
  • Feed: 0.8 mm/rev
  • Cutting speed: 12-15 m/min
  • Depth of cut: 6.4 mm
  • Tool material: T-5
• Finishing in aged condition (carbide):
  • Feed: 0.2 mm/rev
  • Cutting speed: 12-30 m/min
  • Depth of cut: 1.3 mm
  • Tool material: C-2
• Finishing in aged condition (high speed steel):
  • Feed: 0.2 mm/rev
  • Cutting speed: 4-6 m/min
  • Depth of cut: 1.3 m/min
  • Tool material: M-36

We deliver this steel alloy as:

• Pipes
• Bars
• Forgings

Replacements, equivalents and other designations:

Inconel® alloy 925, Inconel® 925, Alloy 925, H09925, NS2401, N09925, VDM® Alloy 925, Nicrofer 4320 Ti, ASTM B 1007 (N09925) / ASME SB-1007 (N09925), ASTM B 1020 (N09925) / ASME SB-1020 (N09925), ASTM B 637 (N09925) / ASME SB-637 (N09925), ASTM B 805 (N09925) / ASME SB-805 (N09925), ASTM B 872 (N09925) / ASME SB-872 (N09925), ASTM B 983 (N09925) / ASME SB-983 (N09925)