Alloy 625 / NA21 / N06625

N06625 / NA21 is a nickel chromium alloy, with additions of molybdenum niobium and tantalum to improve the corrosion resistance and mechanical strength without the need for a heat treatment. The annealed condition or Grade 1 material gives the best combination of strength, hardness and fatigue strength.

Often referred to as Alloy 625 it also offers an excellent resistance to pitting, crevice corrosion, stress corrosion, corrosion fatigue and erosion corrosion whilst retaining a high proportion of its strength and toughness from cryogenic temperatures up to 815ºC. It is very resistant to a wide range of organic and mineral acids combined with good corrosion resistance to high temperature sulphides and chlorides. It also offers a very high resistance to high temperature oxidation and carburisation.

The corrosion performance of Alloy 625 combined with its high strength at elevated temperatures means it has been successfully employed in chemical process industries, power generation, offshore sour oil and gas production, waste incineration, phosphoric acid production, nuclear fuel processing, high temperature environments and aerospace.

Related Standard Specifications

BS3076: NA21

AMS 5666

ASTM B446 N06625

Alloy 625

2.4856

 

Chemical Composition

Nickel

58.0% min

Molybdenum

8.0-10.0%

Chromium

20.0-23.0% min

Carbon

0.10% max

Iron             

5.0% max

Silicon

0.50% max

Niobium+Tantalum

3.15-4.15%

Manganese

0.50% max

Aluminium

0.40% max

Titanium

0.40% max

Sulphur        

0.015% max

Phosphorus

0.015% max

Cobalt          

1.00 max (if determined)

 

 

Key Features

  • Very high mechanical strength
  • Excellent corrosion & pitting resistance
  • Resistance to oxidation UPTO 980ºC
  • High Fatigue strength
  • Excellent high temperature strength
  • Resistance to chloride stress corrosion cracking

 Minimum Mechanical Properties (cold worked, annealed <100mm)

UTS                                          

830 N/mm² min        

0.2% PS                                     

415 N/mm² min

Elongation                                  

30 % min                

 Physical Properties (aged condition)

Melting Point                              

1350°C

Density

8.44 g/cm³

Thermal conductivity

9.8 W/m°C

Thermal expansion coefficient (20-200°C)

12.8 x 10-6

Electrical Resistivity                              

132 microhm / cm

Youngs Modulus                                   

207 GPa

Magnetic Permeability

<1.001

 Fabrication Properties

Hot Working Temperature                        

1050-1170°C

Hot Formability                  

Good

Cold Formability

Okay

Machinability rating                               

Okay

Joining Methods

TIG Welding  

Good

MIG Welding

Good

Typical Applications

Alloy 625 is mainly utilised in the chemical industry for flue gas desulphurisation plant, flare stacks, offshore sour oil and gas production, waste incineration, phosphoric acid production and nuclear fuel processing. Components include marine propeller blades, submarine auxiliary propulsion motors, quick disconnect fittings, exhaust ducts, sheathing for subsea communication cables, submarine transducer controls, springs, seals, bellows for submerged controls, electrical cable connectors, flanges, exhaust systems, fuel and hydraulic tubing, spray bars, bellows, turbine shroud rings, heat exchanger tubing, bubble caps, reaction vessels, valve and valve trim, pumps, fasteners, springs, seals and nuclear control rod components.

This technical information is given by John Hood & Co.without charge and the user shall employ such information at their own discretion and risk. For more detailed technical advice on temper selection, fabrication, joining, machining, physical and mechanical data please contact us as space does not permit the listing of every feature of the material.