BySIDHESHWAR KUMAR

(107MM024)

Department of Metallurgical and Materials

Engineering

NIT - Rourkela

Ni-based Super alloys:

Processing and its

Application

Contents

Introduction

Hardening Mechanism

Manufacturing

Applications

Substitute

References

Introduction

What is Superalloy?A superalloy is a metallic alloy which can be used at

high temperatures, often in excess of 0.7 Tm

Alloying additions for solution strengthening is by addition

of lower amount of W, Mo, Ta, Nb and for Precipitation

hardening by addition of g and g’ formers like Ti, Al, & Nb.

Types of Super alloy

Ni – Based

Co – Based

Fe-Ni – Based

Why Ni-Based alloys ????

Material

Linear thermal

coefficient, α, at 20

°C (10−6/°C)

Volumetric thermal

coefficient, β, at 20

°C (10−6/°C)

Aluminum 23 69

Copper 17 51

Iron 11.1 33.3

Stainless steel 17.3 51.9

Steel 11.0 ~ 13.0 33.0 ~ 39.0

Nickel 13 39

Invar 1.2 3.6

Hardening Mechanism

Solid Solution Strengthening

Precipitation Hardening

Major phases in Nickel superalloys

Gamma (g)

Gamma Prime (g')

Carbides

Topologically Close-Packed Phases

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.

SEM micrograph of minor microstructural

constituents of the alloy in the g matrix.

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.

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.

Metal Carbides

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.

The Shearing of γ' Precipitates

A dislocation cutting a

particle

During Incoherency

The investment shell for

casting a turbocharger

rotor.

A view of the interior

investment shows

the smooth surface

finish.

The completed work piece of

turbocharger rotor.

Industrial requirement

Cost effective

100 000 hrs. creep lifetime under 100 MPa at

750 C

Stable at service temperature

Forgeable & Weldable

Corrosion resistance

Toughness

0

200

400

600

800

1000

0 200 400 600 800 1000 1200

Temperature / °C

Yie

ld s

tress /

MP

a

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.

Type of

enginesOxidation

Hot

corrosion

Inter

diffusion

Thermal

fatigue

Aircraft

enginessevere moderate severe severe

Land-based

power

generation

moderate severe moderate light

Marine

enginesmoderate severe light moderate

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

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

Gas Turbine for marine propulsion

Pressurized water reactor vessel head

Gas Turbine at thermal power plants

Rocket Motor Engine

Nickel-based superalloy, about 65% of gamma-prime

precipitates in a polycrystalline gamma matrix.

Turbine Blades (Jet Engine)

Substitutes

Carbon fiber-reinforced carbon

FRP Materials

Glass fibers

Carbon fibers

Kevlar fibers

Novalac (Epoxy)

Vinyl ester resins

References

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continuously cast Ni-based superalloy GMR 235, Journal of Materials

Processing Technology 186 (2007) 200–206

(2) 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

(3) 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

(4) De-Guang Shang, Guo-Qin Sun, Jian-Hua Chen, Neng Cai, Chu-Liang Yan,

Multiaxial fatigue behavior of Ni-based superalloyGH4169 at 650 ◦C,

Materials Science and Engineering A 432 (2006) 231–238.

(5) Wei Zhao, Lin Liu, Structural characterization of Ni-based superalloy

manufactured by plasmatransferred arc-assisted deposition, Surface &

Coatings Technology 201 (2006) 1783–1787

(6) Kai Song, Mark Aindow, Grain growth and particle pinning in a model Ni-

based superalloy, Materials Science and Engineering A 479 (2008) 365–372.

Cont.... Li Liu, Ying Li, Fuhui Wang, Influence of nanocrystallization on passive

behavior of Ni-based superalloy in acidic solutions, Electrochimica Acta

52 (2007) 2392–2400.

L.R. Liu, T. Jina, N.R. Zhaoa, Z.H. Wang, X.F. Suna, H.R. Guana, Z.Q. Hua,

Effect of carbon addition on the creep properties in a Ni-based single

crystal superalloy, Materials Science and Engineering A 385 (2004) 105–

112.

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superalloy at 900 °C in air and water vapor, Surface & Coatings Technology

202 (2007) 140–145.

T.S. Sidhu, S. Prakash, R.D. Agrawal, Hot corrosion studies of HVOF

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Cont…

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G.S. Hillier and H.K.D.H. Bhadeshia, The Homogenisation of Single-Crystal Superalloys, The Metals Society, London, 1984, pp. 183-187.

H. Harada, A. Ishida, Y. Murakami, H. K. D. H. Bhadeshia and M. Yamazaki, Atom Probe Microanalysis of a Nickel-base Single Crystal Superalloy, Applied Surface Science, Vol. 67, 1993, 299-304.

Thank You