What Are Exotic Alloy Steels?
What are Exotic Alloy Steels?
Exotic alloy steels are specialised steels that have extremely little iron content with the main element being nickel or cobalt. They are extremely hard, durable and possess the ability to strongly resist oxidation.
Inconel X-750
This nickel-chromium alloy is used most commonly in high temperature and corrosive environments. Open air heat treatment of this super alloy can produce oxidation. This often results in a black ash residue.
An atmosphere controlled environment eliminates oxidation and produces a component with no residue. Rings and springs manufactured from Inconel have a blue / silver-grey colour and exhibit no magnetism.
Composition (with traces of phosporus (P) and sulphur (S) not exceeding 0.015% each);
Iron (Fe) 5.00 to 9.00%, carbon (C) 0.02 to 0.10%, 1.00% maximum cobalt (Co), manganese (Mn) 1.00% maximum, chromium (Cr) 14.00 to 17.00%, titanium (Ti) 2.25 to 2.75%, aluminium (Al) 0.4 to 1.0%, copper (Cu) 0.5%, silicon (Si) 0.50% maximum, niobium (Nb) + tantalum (Ta) 0.70 to 1.20%, nickel (Ni) 69.00 to 70.00%.
A286 Alloy
This alloy exhibits similar properties to Inconel X-750 spring temper in applications up to 1000° F. Its spring temper condition is obtained by precipitation hardening also known as ‘aging’. This material has a blue / silver-grey colour and exhibits no magnetism.
This alloy is ductile, non-magnetic and has high strength. It is used for low temperature applications; temperatures ranging from above room temperature down to at least -320°F (-196°C).
The alloy can be used in water solutions where moderate corrosion applications apply.
Composition (with traces of phosporus (P) and sulphur (S) not exceeding 0.015% each);
Iron (Fe) 11.08% to 23.9%, carbon (C) 0.08% maximum, 1.00% maximum cobalt (Co), manganese (Mn) 0.35% maximum, molybdenum (Mo) 2.8 to 3.3%, columbium (Nb) 4.75 to 5.50%, chromium (Cr) 17.00 to 21.00%, titanium (Ti) 0.65 to 1.15%, aluminium (Al) 0.20 to 0.80%, boron (B) 0.006% maximum, copper (Cu) 0.3% maximum, silicon (Si) 0.35% maximum, tantalum (Ta) 0.05% maximum, nickel (Ni) 50.00 to 55.00%.
Elgiloy
Elgiloy, like A286 alloy, exhibits no magnetism but is also known for its excellent resistance to corrosive environments, elevated temperature resistance and high strength. It is blue / brown in colour due to its heat treatment.
Elgiloy has similar mechanical properties to high carbon spring steel (music wire). These properties are often superior to stainless steel and other nickel alloys. In some (medical) applications it can be used in place of titanium. It is also used to make springs that are corrosion resistant and exhibit high strength, ductility, and good fatigue life.
Composition (with traces of phosporus (P) and sulphur (S) not exceeding 0.015% each);
Iron (Fe) 11.32 to 20.45%, carbon (C) 0.02 to 0.10%, 39.00 to 41.00% cobalt (Co), manganese (Mn) 1.50 to 2.50% maximum, chromium (Cr) 19 to 21%, molybdenum (Mo) 6.00 to 8.00%, silicon (Si) 0.15% maximum, nickel (Ni) 14 to 16%.
Waspaloy
Often encountered in extreme environments. It is common in gas turbine blades, seals, rings, shafts and turbine disks. It is an age-hardenable, nickel-based superalloy with excellent strength properties through temperatures of roughly 980°C (1800°F).
Other characteristics of waspaloy include good corrosion resistance, as well as being relatively impervious to oxidation making it well suited for service in extreme environments.
Composition (with traces of phosporus (P) and sulphur (S) not exceeding 0.015% each);
Iron (Fe) 2.00% maximum, carbon (C) 0.02 to 0.10%, manganese (Mn) 0.1% maximum, chromium (Cr) 18 to 21%, molybdenum (Mo) 3.50 to 5.00%, cobalt (Co) 12 to 15%, copper (Cu) 0.10%, aluminium (Al) 1.20 to 1.60%, titanium (Ti) 2.75 to 3.25%, zirconium (Zr) 0.02 to 0.08, boron (B) 0.003 to 0.01, silicon (Si) 0.15% maximum and the balance being nickel (Ni), minimum 48.42%.
