This document discusses superalloys, which are metallic alloys that exhibit excellent mechanical strength and creep resistance at high temperatures. It describes the composition of common superalloys such as nickel, cobalt, and iron-based alloys. The key strengthening mechanisms in superalloys are solid solution strengthening and precipitation hardening using elements like titanium and aluminum. Major phases in nickel superalloys include the gamma, gamma-prime, and carbide phases. Properties of superalloys include high temperature strength and corrosion/oxidation resistance. Superalloys find applications in jet engines, nuclear reactors, and industrial gas turbines where they are used for components like turbine blades.

1. SUPER ALLOYS
PREPARED BY:
Syed Nooruddin (D-12-MT-347)
Ali Asad Zaheer(D-12-MT-355)
Khurram Khan(D-12-MT-349)
Faisal Shabir (D-12-MT-384)
Manzoor Ahmed (D-12-MT-385)
Department of Metallurgy & Materials
Dawood University Of Engineering & Tech.(Karachi)

3. Contents
 Introduction
 Development
 Composition
 Types
 Processing & Properties
 Applications
 References

4. Introduction
What is Superalloy?
A superalloy is a metallic alloy which can be
used at high temperatures, often in excess of 0.7
Tm ( absolute melting temperature)
 Superalloy is an alloy that exhibits
excellent mechanical strength and creep
resistance at high temperatures.
 Alloying additions for solution
strengthening is by addition of lower
amount of W, Mo, Ta, Nb & for
Precipitation hardening by addition of of
g and g’ formers like Ti, Al & Nb.
 Examples of such alloys
are Hastelloy, Inconel, Waspaloy, Rene
alloys, Haynes alloys, Incoloy, MP98T, TMS
alloys, and CMSX single crystal alloys.

5. Development of Super Alloys
 Superalloys develop high temperature strength through Solid
solution strengthening(SSS).
 SSS is a type of alloying that can be used to improve the strength of
the metals. It is the hardening mechanism process.
 The technique works by adding atoms of one element (alloying
element) to the crystalline lattice of another element (the base
metal).

6. Composition of some Super alloys

7. Types of Super Alloys
 Ni – Based Superalloy.
 Co – Based Superalloy.
 Fe-Ni – Based Superalloy.

8. Iron based Super Alloys:
(a) 9-38 % nickel
(b) 15-22 % chromium
(c) 32-67 % iron
Common type of Iron based alloy is Incoloy
series.
 Iron based Super alloys are characterised by high temperature as
well as room temperature strength.
 Apart from this, it will have good resistance to creep , oxidation,
corrosion and wear.
 Oxidation resistance increases with chromium content.

9. Cobalt based Super 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.

10. 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

11. Major phases in Nickel Superalloys
 Gamma (g)
 Gamma Prime (g')
 Carbides
 Topologically Close-Packed Phases

12. Gamma (g)
The continuous matrix (called gamma) is an face-centered-cubic
(FCC) nickel-based austenitic phase that usually contains a high
percentage of solid-solution elements such as Co, Cr, Mo, and W.

13. SEM micrograph of minor microstructural
constituents of the alloy in the g matrix.

14. Gamma Prime (g')
 The primary strengthening phase in nickel-based superalloys is Ni3(Al,Ti), and
is called gamma prime (g '). It is a coherently precipitating phase (i.e., the
crystal planes of the precipitate are in registry with the gamma matrix) with
an ordered FCC crystal structure.

15. Carbides
Carbon, added at levels of 0.05-0.2%, combines with reactive
elements such as titanium, tantalum, and hafnium to form carbides
(e.g., TiC, TaC, or HfC). During heat treatment and service, these begin
to decompose and form lower carbides such as M23C6 and M6C,
which tend to form on the grain boundaries. These common carbides
all have an fcc crystal structure.
The general opinion is that in superalloys with grain boundaries,
carbides are beneficial by increasing rupture strength at high
tempeature.

16. Topologically Close-Packed Phases
These are generally undesirable, brittle phases that can form during
heat treatment or service.
TCPs (Sigma, Mu, Laves, etc.) usually form as plates (which
appear as needles on a single-plane microstructure).
TCPs are potentially damaging for two reasons: they tie up g
and g ' strengthening elements in a non-useful form, thus reducing
creep strength, and they can act as crack initiators because of their
brittle nature.

17. True stress–true strain flow curves for the Ni-based superalloy under different strain rates
and temperatures: (a) 1050 °C, (b) 1100 °C, (c) 1140 °C, and (d) 1180 °C.

19. Properties of Superalloys
 Excellent mechanical strength and wear resistance at high
temperature.
 Resistance to corrosion and oxidation at very high temperature.
 Good surface stability.
 High Impact toughness

20. APPLICATIONS
Nickel-based super alloys are widely used in load-bearing
structures to the highest homologous temperature
0.9 Tm, or 90% of their melting point.
 Aerospace
 Turbine blades and jet/rocket engines
 Marine industry
 Submarines
 Nuclear reactors
 Heat exchanger tubing
 Industrial gas turbines

21. A jet engine (Rolls-Royce Trent 800)
 Intermediate pressure compressor
(IPC),
 High pressure compressor (HPC),
 High pressure turbine (HPT),
 Intermediate pressure turbine (IPT),
 Low pressure turbine (LPT),
and the pressure and temperature
profiles along the engine.

22. Gas Turbine for Marine Propulsion

23. Pressurized water reactor vessel head

24. Gas Turbine at thermal power plant

25. Rocket Motor Engine

26. Turbine Blades (Jet Engine)
Nickel-based superalloy, about 65% of gamma-prime
precipitates in a polycrystalline gamma matrix.

27. References
 http://www.msm.cam.ac.uk/phase-trans/2003/Superalloys/superalloys.html.
 http://www.patentstorm.us/patents/5366695.html
 Manufacturing process for engineering materials by Kalpakjian
 Material science and Engg by William Callister
 F. Zupani, T. Bonˇcina, G. Lojen, B. Markoli, S. Spai, Structure of the continuously
cast Ni-based superalloy GMR 235, Journal of Materials Processing Technology
186 (2007) 200–206
 Dayong Cai, Liangyin Xiong, Wenchang Liu, Guidong Sun, Mei Yao,
Development of processing maps for a Ni-based superalloy, Materials
Characterization 58 (2007) 941–946
 F. Zupanic, T. B oncina, A. Krizman, B. Markoli, S. Spaic, Microstructural
constituents of the Ni-based superalloyGMR 235 in the as-cast condition, Scripta
Materialia 46 (2002) 667–672