Alloy 625 (UNS N06625)


Alloy 625 is a nickel-chromium-molybdenum-niobium alloy (NiCr22Mo9Nb), supplied in the hot worked and annealed condition. It achieves high-strength levels from the solid solution effects of Molybdenum and Niobium (Colombium) from room temperature up to 800°C.

It is particularly useful in situations where oxidation resistance and avoidance of pitting is required. In the annealed condition, it is fully austenitic and is suitable for machining. It provides excellent corrosion resistance in a wide variety of severe corrosive environments due to its high alloy content.

Key Features:

  • Good strength/ductility properties from sub-zero temperatures to over 980°C
  • Excellent corrosion and fatigue resistance in a wide variety of corrosive environments including seawater and industrial acids
  • Non-magnetic and spark resistant
  • Resistant to high temperature oxidation and carburisation
  • Excellent resistance to stress corrosion cracking


  • Wellhead components
  • Sheathing, Fasteners, Clamps
  • Downhole equipment for corrosive/sour service
  • Propellers and Shafts
  • Propulsion Motors
  • Fasteners
  • Reactor core & control rod components
  • Chemical process equipment

Chemical Composition:

Cr Ni Mo Co Nb (+Ta) Ti W Cu C Mn N Si P S Fe Al
Min 20.00 58.00 8.00 3.15
Max 23.00 10.00 1.00 4.15 0.40 0.10 0.50 0.50 0.015 0.015 5.00 0.40

Mechanical Properties:

Bars up to and including 4” diameter or section Bars above 4” diameter or section
0.2% Proof Stress 415 N/mm2 60ksi 345 N/mm2 50ksi
Tensile Strength 830 N/mm2 120ksi 760 N/mm2 110ksi
Elongation, 5.65√S0 and 4D 30% 25%
Reduction of Area 35% 35%
Hardness (Brinell)


  1. Tensile testing shall be carried out in accordance with ASTM A370 or EN10002-1
  2. Minimum properties quoted (tested at room temperature in a longitudinal direction)
  3. Testing performed on each melt of material per heat treatment batch

Physical Properties:

Density (Kg.m-1) 84.4
Magnetic Permeability (20°C) <1.001
Curie Temperature (°C) -196
Young’s Modulus (N/mm2) 207.5
Specific Heat, 20°C (J/(g.K)) 410
Specific Electrical Resistance, 20°C (Ω-m) 0.0129
Thermal conductivity, 20°C (W/(m.K)) 9.9
Mean coefficient of thermal expansion, 20-100°C (/K) 12.8 x 10-6


Datasheet - NA-Alloy 625

Datasheet - NA-Alloy 625