Inconel is the brand name for a group of 20 austenitic nickel-chromium alloys, made by Special Metals Corporation. Each Inconel alloy has been developed with its own specific properties. Here are a few of the most commonly used Inconel alloys:
Inconel 600 – Nickel-chromium alloy with applications in food processing resistant to corrosion by chloride ions and water.
Inconel 625 – Developed for easier welding.
Inconel 690 – Low cobalt content making it ideal for nuclear applications
Inconel 718 – Comprised of nickel, chromium and traces of molybdenum, iron, niobium, aluminium and titanium, this alloy is strong, flexible and can perform well in temperatures of up to 1,300 degrees Fahrenheit.
All Inconel alloys are resistant to oxidation, however, it is in high temperature environments where Inconel outperforms aluminium and steel. This is because, when it is heated, Inconel forms a passivating oxide layer that protects the surface. Different types of Inconel differ in terms of resistance to corrosion, malleability, elasticity and how they react to
It’s during the production process that Inconel alloys take on their temperature resistance. Depending on the alloy, either solid solution strengthening or precipitation strengthening is used. However, due to rapid work hardening, Incomel can be difficult to shape or machine, requiring a slow cut with a hard tool. Inconel parts can be roll threaded using induction heat. Because of its superior temperature resistance, gas tungsten arc welding and electron beam welding are recommended.
Typically, Inconel alloys are used in extreme temperature environments, such as in the chemical industry. However, it is also found in:
- Food processing
- Gas turbine blades
- Nuclear industry
- Power generation
Inconel was first developed in the 1940s by an English company called Wiggin Alloys that was working on an alloy to handle the high temperatures created by the Whittle jet engine.
Chemical Composition of Inconel 625
|Mo||8 – 10%|
|Cr||20 – 23%|
|Nb+Ta||3.15 – 4.15%|
Typical Properties of Inconel 625
|Density||8.44 g/cm3||0.305 lb/in3|
|Melting point||1350 °C||2460 °F|
|Co-Efficient of Expansion||12.8 μm/m.°C
|Modulus of Rigidity||79 kN/mm2||11458 ksi|
|Modulus of Elasticity||205.8 kN/mm2||29849 ksi|