3. Classification of Superalloys
• These alloys have austenitic FCC structure which have
base alloying element of nickel, cobalt and iron.
• Further they are classified on the basis of pre-
dominant element present in it.
• Alloying elements are Fe, Co, Ni, Cr, W (tungsten),
Mo (molybdenum), Nb (niobium) and Ta (tantalum).
• Iron based alloys:
(a) 9-38 % nickel
(b) 15-22 % chromium
(c) 32-67 % iron
Common type of Iron based alloy is Incoloy
series.
4. • Cobalt based alloys:
(a) Up to 35% nickel
(b) 19-30 % chromium
(c) 30-65 % cobalt
Cobalt based alloys can retain their strength at
high temperature but they are not as strong as
nickel based alloys.
5. • Nickel based alloys:
(a) 38-76% nickel
(b) Up to 27 % chromium
(c) Up to 20 % cobalt.
Some of the common type of nickel based alloys
are Nimonic, Hastelloy and Inconel.
These are the most common types of
Superalloy which are widely used in turbine
blades
6. Properties of Superalloys
• Excellent mechanical strength and wear
resistance at high temperature.
• Resistance to corrosion and oxidation at very
high temperature.
• Good surface stability.
7. Applications of Superalloys
• In Aerospace : blades of turbines and in
jet/rocket engines.
• In Marine : wide use in Submarines.
• In Chemical processing industries.
• Heat exchanger tubing
• Industrial gas turbines
• Nuclear Reactors
