Nickel alloys

Nickel will alloy readily with many other metals, including chromium, iron, molybdenum and copper. This allows for a wide variety of alloys that demonstrate outstanding resistance to corrosion and high-temperature scaling, exceptional high-temperature strength and other unique properties, such as shape memory and low coefficient of expansion.

The following is a simplistic categorisation of the various nickel alloy types.

  • Wrought Nickel

    Pure nickel UNS N02200 is used in the chemical industry for its corrosion resistance - particularly to alkalis. It is also used for its properties in shielding against electromagnetic interference and in transducers.

  • Nickel-Iron Alloys

    These are used as soft magnetic materials, as glass-to-metal seals and as materials with defined thermal expansion properties.
    Invar® (UNS K93600), with 36% nickel and the remainder iron, is unique in having an almost zero coefficient of thermal expansion around room temperature. This makes it valuable where high dimensional stability is required, such as in precision measuring instruments and thermostat rods. It is also used at cryogenic temperatures because of its very low thermal expansion rates.
    Alloys containing 72-83% nickel have the best soft magnetic properties and are used in transformers, inductors, magnetic amplifiers, magnetic shields and memory storage devices.

  • Nickel-Copper Alloys

    These are highly resistant to corrosion by alkaline solutions, non-oxidizing salts and seawater. The best-known is Alloy 400.

  • Nickel-Molybdenum Alloys

    These are highly resistant to reducing acids in the absence of oxidizing ions, such as ferric and cupric or dissolved oxygen. The best-known is Alloy B-2.

  • Nickel-Chromium Alloys

    These are characterised by their high resistance to corrosion at both normal and high temperatures (resistance to scaling), good high-temperature strength and high electrical resistance. There are three main groups of alloys:

    • Ni-Cr (and also Ni-Cr-Fe) alloys with high electrical resistance for heating elements, such as 70-30 (UNS N06008) and C-Grade (UNS N06004)
    • Ni-Cr alloys (with Fe and other alloying elements) with good corrosion resistance. The best-known are Alloy 600 (UNS N06600) and Alloy 601 (UNS N06601)
    • Ni-Cr alloys with high-temperature strength and creep resistance, mostly age-hardenable, such as Alloy X-750 (UNS N07750)
  • Nickel-Chromium-Iron Alloys

    There are basically two groups of alloys:

    • Ni – Cr – Fe alloys with excellent strength at high temperature and the ability to resist oxidation, carburisation and other types of high-temperature corrosion. The best-known is alloy 800 (UNS N08800) and its variants 800H (UNS N08810) and 800HT (UNS N08811). (Recently, these alloys were classified as stainless steels reflecting their high Fe content)
    • Ni – Cr – Fe (with Mo and Cu) alloys with excellent corrosion resistance in specific applications. Probably the best-known is alloy 825 (UNS N08825), which offers exceptional resistance to sulphuric acid. Alloy G-3 (UNS N06985) offers exceptional corrosion resistance to commercial phosphoric acids as well as many complex solutions containing highly oxidizing acids.
  • Nickel-Chromium-Molybdenum Alloys

    These are highly corrosion-resistant, of which Alloy C-276 (N10276) is the best-known. They offer exceptional resistance to reducing acids such as hydrochloric and sulphuric. There are a number of variants based on this composition, which have modified the Cr and Mo levels and, in some cases, added Cu or W in order to extend the corrosion resistance to conditions that are more oxidising or more reducing. These include Alloy C-22 (N06022), Alloy 59 (N08059), Alloy C-2000 (UNS N06200), and Alloy 686 (N06686).

  • Nickel-Chromium-Cobalt Alloys

    The addition of cobalt and molybdenum imparts solid-solution strengthening and high levels of creep-rupture strength to alloy 617 (UNS N06617). The addition of cobalt to HR-160 (N12160) provides outstanding resistance to various forms of high-temperature corrosion attacks, such as sulphidation and chloride attack in both reducing and oxidizing atmospheres.

  • Nickel-Titanium Alloys

    55% nickel-titanium alloy (UNS N01555) (also known as Nitinol) has shape-memory properties. When formed at one temperature and then deformed at a lower one, it regains its original form when reheated. The transition temperatures can be adjusted through careful control of the composition. Medical devices and specialised connectors are two of specific the applications. The same alloy can also undergo considerable elastic deformation and still return to its original shape (super-elastic property). This property has been exploited for applications as diverse as spectacle frames and shock absorbers that provide earthquake resistance in historic stone buildings.

Nominal composition of various nickel alloys:

Alloy name UNS % Ni % Cr % Fe % Mo % Cu % Co % Other
200 N02200 99 min            
Invar K93600 36   64        
400 N04400 65 32          
B-2 N10665 68   2 28      
70-30 N06008 70 30          
C-Grade N06006 60 16 bal        
600 N06600 76 16 8        
601 N06601 60 23 bal       Al - 1.3
X-750 N07750 70 15 7      

Ti - 2.5

Al - 0.7

Nb - 1.0

825 N08825 42 21 25 3 2    
G-3 N06985 bal 22 20 7 2    
800 N08800 32 21 45       W - 3.5
C-276 N10276 bal 15 5 16      
C-22 N06022 bal 21 4 13      
59 N06059 bal 23 1.5 max 16      
C-2000 N06200 bal 23 3 max 16 1.6    
686 N06686 bal 21 2 max 16     W - 3.7
617 N06617 44.5 min 22 3 max 9   12  
HR-160 N12160 bal 28 3.5 max     30 Si - 2.75
Nitinol N01555 55           Ti - 45



Alloy Type UNS %Cr %Ni %Mo %Cu %Fe  
304L S30403 18 8


- bal Most common stainless steel used for potable water treatment and food contact.
316L S31603 16 10 2.1 - bal Addition of Mo provides greater resistance to chlorides and acidic solutions. Used in coastal regions, in water treatment and in the chemical processing industry.
2205 S32205 22 5.7 3.1 - bal Even greater corrosion resistance than 316L. Can be used in place of 316L, but its greater strength can mean weight reduction. May be  substituted for 316L if it fails in service.
2507 S32750 25 7 4 - bal Even greater corrosion resistance than 2205. Useful corrosion resistance to seawater.
254 SMO S31254 20 18 6.1 - bal Corrosion resistance similar to 2507, also possessing useful corrosion resistance to seawater.
Alloy 20 N08020 20 33 2.1 3.2 bal Cu bearing stainless steel with useful corrosion resistance to all concentrations of sulphuric acid.
310S S31008 25 20 - - bal High chromium stainless steel with excellent resistance to high-temperature oxidation.
800H N08810 20 32 - - bal Stainless steel with excellent high-temperature strength and useful resistance to high-temperature oxidation.
625 N06625 21 bal 9 - 3 Well-known nickel alloy with excellent high-temperature strength and outstanding aqueous corrosion resistance.
C-276 N10276 15 bal 16 - 5 One of the best-known nickel alloys with excellent corrosion resistance to reducing acids.
600 N06600 16 76 - - 8 Useful resistance to high-temperature corrosion and caustic solutions.
Alloy 400 N04400 - 65 - 32 - Most common uses are in marine and chemical processing.


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