2.08

Nickel Alloys: Properties and Characteristics

T. Yonezawa
Tohoku University, Japan

ß 2012 Elsevier Ltd. All rights reserved.

2.08.1

Introduction

234

2.08.2
2.08.2.1
2.08.2.1.1
2.08.2.1.2
2.08.2.2
2.08.2.2.1
2.08.2.2.2
2.08.2.3
2.08.2.3.1
2.08.2.3.2
2.08.2.4
2.08.2.4.1
2.08.2.4.2
2.08.3
2.08.3.1
2.08.3.2

2.08.3.3
2.08.3.4
2.08.3.5
2.08.3.6
2.08.3.7
2.08.3.7.1
2.08.3.7.2
2.08.3.8
2.08.4
2.08.4.1
2.08.4.2
2.08.4.3
2.08.4.4
2.08.4.5
2.08.4.6
2.08.4.6.1
2.08.4.6.2
2.08.4.6.3
2.08.5
References

Nickel and Nickel Alloy Systems
Ni and Ni–Cu Alloys
Chemical compositions, physical properties, and mechanical properties
Applications to nuclear power industrial fields
Ni–Cr–Fe and Ni–Cr–Fe–Mo Alloys
Chemical compositions, physical properties, and mechanical properties
Applications to nuclear power industrial fields
Ni–Mo–Fe, Ni–Mo–Cr–Fe, and Ni–Cr–Mo–Fe Alloys
Chemical compositions, physical properties, and mechanical properties

Applications to nuclear power industrial fields
Other Ni-Based Alloys
Chemical compositions, physical properties, and mechanical properties
Applications to nuclear power industrial fields
Fabrication of Ni-Based Alloys
Melting
Hot Forming
Cold Forming
Heat Treatment
Descaling and Pickling
Grinding and Machining
Welding
Weldability
Welding materials and example of welding condition
Applicable Specifications
Corrosion Resistance and Stress Corrosion Cracking Resistance
In Air and in Water
In Seawater and Chloride Solution
In Caustic Solutions
In Hydrochloride Gas, Chlorine, and Hydrofluoric Acid
In High-Temperature Water
In High-Temperature Gases
Oxidation
Nitriding
Sulfidation
Summary

234
235
235

239
241
241
244
250
250
253
253
253
253
254
254
254
255
256
257
257
257
257
257
258
258
258
261
262
262
262
263
263
264

264
265
265

Abbreviations
ASME
ASTM
BWR

American Society of Mechanical
Engineering
American Society for Testing and
Materials
Boiling water reactor

CRDM
EBW
fcc
FCAW
GTAW
HTGR

Control rod drive mechanism
Electron beam welding
Face-centered cubic
Flux cored arc welding
Gas tungsten arc welding
High-temperature gas-cooled reactor

233



234

Nickel Alloys: Properties and Characteristics

Precipitation hardening at about 715 C
after solution annealing at a high
temperature near 1075 C
HTTR
High-temperature engineering HTGR test
reactor
IGSCC Intergranular stress corrosion cracking
LBW
Laser beam welding
MA
Mill-annealed
MAG
Metal active gas welding
MIG
Metal inert gas welding
PWR
Pressurized water reactor
PWSCC Primary water stress corrosion cracking
SAW
Submerged arc welding
SCC
Stress corrosion cracking
SG
Steam generator

SMAW Shielded metal arc welding
TT
Thermally treated or thermal treatment
HTH

2.08.1 Introduction
Nickel was first used as an alloying element for steels
in the mid-eighteenth century. The development of
corrosion-resistant steels was started in the nineteenth
century.1,2 These studies led to the development of
various kinds of stainless steels, particularly in the
early 1900s. Particularly, the 300 series austenitic stainless steels were developed and became the ‘most widely
used tonnage’ materials in the twentieth century.
The nickel–copper Alloy 400 (Monel 400, UNS
N04400) was developed as the first nickel-based alloy
at the beginning of the twentieth century.3 This alloy
was developed as an alternative chloride-corrosionresistant material to austenitic stainless steel.
Nickel is a less noble element than copper; however, it is more noble than iron and zinc. It exhibits
higher corrosion resistance than iron in most environments due to the formation of denser and more
protective corrosion films with superior passivation
characteristics compared to iron.
Nickel has superior corrosion resistance in caustic
or nonoxidizing acidic solutions, and in gaseous halogens. It can be relatively easily alloyed with various
elements such as chromium, molybdenum, iron, and
copper. Many nickel-based alloys have been developed and applied as corrosion-resistant alloys in various environments, as well as creep-resistant alloys in
high-temperature applications.4
Based on their excellent properties, nickel-based
alloys have been widely applied in a number of fields,
for example, the aerospace industry, chemical industries, and electricity generation plants. In the nuclear


power industry, nickel-based alloys have been used in
pressurized water reactors (PWRs) and boiling water
reactors (BWRs) since their initial development in
the early 1950s. In particular, Alloys X-750 (UNS
N07750) and X-718 (UNS N07718) have been widely
applied, for example, for jet-engine blades, due to
their excellent creep strength. A high-creep-strength
material is one that is highly resistant to stress relaxation at high temperatures. Alloys X-750 and 718
have therefore been applied as bolting and spring
materials for PWRs and BWRs.
Alloy 600 (UNS N06600) has superior resistance to
stress corrosion cracking (SCC) in boiling 42% MgCl2
solution as high-chloride solutions.5 In the Shippingport and Yankee Rowe reactors, 347 stainless steel
was used as a steam generator (SG) tube material.
(The Shippingport reactor was the first full-scale
nuclear powered electricity generation plant (prototype reactor), and the Yankee Rowe reactor was the first
commercial PWR.) Beginning with the Connecticut
Yankee PWR, the next electricity generation plant,
Alloy 600 was used as the SG tube material, and then
subsequently applied in PWRs worldwide, due to its
superior SCC resistance in high-chloride solutions.
Among the other superior properties of Alloy 600,
its thermal expansion coefficient is noted to be between
that of ferritic steels and austenitic steels. Based on this,
the residual stress and strain for dissimilar weld joints
of ferritic steels and austenitic steels can be minimized
by the use of Alloy 600 and its compatible weld metals.
In nuclear power plants, ferritic steels and austenitic
steels are widely used as the main component materials, especially for the pressure boundary. Numerous
dissimilar metal weld joints are therefore found in

nuclear power plants. Alloy 600 and its weld metals
such as Alloys 82, 132, and 182 have also found widespread application in such plants.
Nickel-based alloys were developed not only
as corrosion-resistant materials but also as heatresistant materials. These alloys are suitable for
various components and parts in light water reactors,
heavy water reactors, gas reactors, etc.
The detailed features and various physical properties of these nickel-based alloys are described in the
following sections.

2.08.2 Nickel and Nickel Alloy
Systems
Nickel by itself is a very versatile corrosion-resistant
metal and has a higher strength at elevated temperatures than steel. Nickel forms a complete solid solution


Nickel Alloys: Properties and Characteristics

235

Atomic percent nickel
0

10

20

30

40


50

60

70

80

90

100

1600
1455 ؇C

1400

L

1200

Temperature ( ЊC)

1084.87 ؇C
1000
800
600
354.5 ؇C
65.5


400

354.4 ؇C

Tc

(Cu,Ni)
α1 + α2

200
0
0

10

20

30

Cu

50
60
40
Weight percent nickel

70

80


90

100
Ni

Figure 1 Copper–nickel binary phase diagram.

with copper (as shown in Figure 1), manganese, and
gold.6 Nickel forms a peritectic with iron (as shown in
Figure 2) and eutectics with many elements, such as
chromium (as shown in Figure 3), molybdenum (as
shown in Figure 4), silicon, titanium, aluminum, niobium.6 Nickel can form solid solutions with many elements and intermetallic compound with aluminum,
titanium, niobium, and so on. The ternary constitutional
diagram for the iron–nickel–chromium isothermal section at 650  C shown in Figure 5 indicates a wide region
covered by the face-centered cubic (fcc) structure of
nickel. But the fcc region is shrunk in the ternary
constitutional diagram at 600  C for nickel–chromium–
molybdenum system, as shown in Figure 6. In this alloy
system, sigma phase and other intermetallic phases are
found based on a composition range.6 The effects of
alloying elements on the properties of nickel-based
alloys are summarized in Table 1.
Commercially pure nickel and various nickel-based
alloys are representative of the newly developed materials during the twentieth century. These materials are
typically encountered in various industrial systems,
including chemical and petrochemical processing,
aerospace engineering, fossil fuel and nuclear power
generation, energy conversion, solar energy conversion, thermal processing and heat treatment, oil and
gas production, pollution control and waste


processing, marine engineering, pulp and paper
industry, agrichemicals, industrial and domestic heating, and electronics and telecommunication, among
others.
Various nickel-based alloys, including binary, ternary, and other complex systems, were also developed in the twentieth century. The main features and
applications of these commercially pure nickel and
nickel-based alloys are summarized in Figure 7.
Detailed properties and features of these nickel
and nickel-based alloys are described in the following
sections. The several of these nickel-based alloys
have been applied or designed to various nuclear
reactor materials as shown in Table 2.
2.08.2.1

Ni and Ni–Cu Alloys

2.08.2.1.1 Chemical compositions, physical
properties, and mechanical properties

The chemical compositions of nickel and typical
nickel–copper alloys are shown in Table 3, along
with those of other nickel-based alloys.
Alloy 200 (UNS N02200) is a commercially pure
(99.6%) wrought nickel. Alloy 201 (UNS N02201) is
the low-carbon version of Alloy 200. These alloys
have good mechanical properties and good resistance
to corrosion at low to moderate temperatures in


236


Nickel Alloys: Properties and Characteristics

Atomic percent nickel
0

10

20

30

40

50

60

70

80

90

100

1600
1538 ؇C

1514 ؇C


1400
1394 ؇C

(δ-Fe)

L

1455 ؇C

1440 ؇C
67
0

20

40

60

80 100

800

1200

Tc(α-Fe) Tc(FeNi3)

700

Temperature (ЊC)


600
500

1000

(γ-Fe,Ni)

Tc(γ-Fe,Ni)

400

912 ؇C

300

800
770 ؇C

200

Tc(α-Fe)

0

20

40

60


600

Tc(γ -Fe,Ni)

517 ؇C
73

400

347 ؇C
4.9
(α-Fe)

50

80 100

354.3 ؇C

FeNi3

64

200
0
Fe

10


20

30

40
50
60
Weight percent nickel

70

80

90

100
Ni

Figure 2 Iron–nickel binary phase diagram.

Atomic percent chromium
0

10

20

30

40


50

60

70

80

90

1900

100
1863 ؇C

1700

L

Temperature (ЊC)

1500
1455 ؇C
1345 ؇C
1300

(Cr)

1100

(Ni)
900

700
590 ؇C
γЈ

500
0
Ni

10

20

30

40

50

60

Weight percent chromium

Figure 3 Nickel–chromium binary phase diagram.

70

80


90

100
Cr


Nickel Alloys: Properties and Characteristics

0

10

Atomic percent molybdenum
30
40
50
60

20

70

80

90

100

2700


2623 ؇C

2500
2300
L

Temperature (ЊC)

2100
1900
1700
1500
1455 ؇C

1362 ؇C

1300

1309 ؇C
(Ni)

1100

867 ؇C

Ni4Mo

(Mo)


NiMo

907 ؇C

900

Ni3Mo

700
0
Ni

10

20

30

40
50
60
70
Weight percent molybdenum

80

90

100
Mo


Figure 4 Nickel–molybdenum binary phase diagram.

Cr
10
90
20
80
30

pe
rce
n

αЈ + γ

50

rom
ch

σ

60

40

ium

σ+α

σ+γ

70

nt
rce

pe

ht

60
αЈ + σ

50

ht

We
ig

70

ig
We

t ir
on

αЈ

40

30
80
20
90

α+γ

γ

10

α
Fe

10

20

30

60
40
50
Weight percent nickel

Figure 5 Iron–nickel–chromium ternary phase diagram (at 650  C).

70


80

90

Ni

237


238

Nickel Alloys: Properties and Characteristics

Mo
10
90
20
80

s+α

A+α

α
α

P+

δ+


σ+A

P
δ+

erc
ht
p

A

50
σ

40

A

30

γ+

80

γ+P

γ+

δ


m

70

nu

de

We
ig

A

lyb
mo

P P+

nt

50

60

rce

60

δ


pe

40

70

t
igh
We

en
tn
ick
el

30

20

γ+σ

90
10
γ
Ni

10

20


30

40
50
60
70
Weight percent chromium

80

90

Cr

Figure 6 Nickel–chromium–molybdenum ternary phase diagram (at 600  C).

caustic solutions such as NaOH or dilute deaerated
solutions of common nonoxidizing mineral acids
such as HCl, H2SO4, or H3PO4.7
The mechanical properties of Alloy 200 at elevated temperatures are shown in Figures 8 and 9.3
Alloy 200 is typically limited to use at temperatures
below 315  C. At higher temperatures, Alloy 200
products can suffer from graphitization, which can
severely compromise the properties of the material.
Alloy 200 is susceptible to embrittlement after longterm heating in the range of 425–760  C, due to
carbide precipitation along grain boundaries.4 For
service above 315  C, Alloy 201 is preferred.7
The reason for the good corrosion resistance of
Alloys 200 and 201 is the fact that the standard

oxidation–reduction potential of nickel is more
noble than that of iron and less noble than that of
copper. Due to nickel’s high overpotential for hydrogen evolution, hydrogen is not easily discharged from
any of the common nonoxidizing acids, and a supply
of oxygen is necessary for rapid corrosion to occur.
Hence, in the presence of oxidizing species such
as ferric ions, cupric ions, nitrates, peroxides, or oxygen, nickel can corrode rapidly. The outstanding
corrosion-resistance characteristics of Alloy 200 to

caustic soda and other alkalis have led to its successful use in caustic evaporator tubes.7
The nickel–copper Alloy 400 is a complete solidsolution alloy that can be hardened only by coldworking. Alloy 400 contains about 30–33% copper
in a nickel matrix and has similar characteristics as
those of Alloy 200. It has high strength and toughness
over a wide temperature range and good resistance to
many corrosive environments. Alloy 400 exhibits
excellent resistance to corrosion in many reducing
media. It is also generally more resistant to attack by
oxidizing environments compared to higher coppercontent alloys. It is also widely used in marine applications. Alloy 400 products exhibit low corrosion
rates in flowing seawater, whereas in stagnant conditions, crevice and pitting corrosion can be induced. It
is also resistant to SCC and pitting in most fresh and
industrial waters. Alloy 400 is highly resistant to
hydrofluoric acid at all concentrations and at all
temperatures up to their boiling points. It is therefore
widely used in components for seawater applications,
salt units, crude distillation, and as a structural material in chemical plants.8
Alloy K-500 (UNS N05500) is a precipitationhardened version of Alloy 400. It contains aluminum


Nickel Alloys: Properties and Characteristics


Table 1

239

The effects of alloying elements various properties of nickel-based alloys

Alloying
elements

Main feature for aqueous corrosion

Main feature for high-temperature
applications

Other benefits

Ni

Provides corrosion resistance to caustic
solutions and dilute deaerated solutions
of nonoxidizing mineral acids. Improves
chloride SCC
Provides resistance to oxidizing media
Enhances localized corrosion resistance

Stabilization of austenitic phase.
Provides precipitation of g0

Thermal stability
and fabricability


Cr

Mo

Provides resistance to reducing media

W

Enhances localized corrosion resistance
Behaves similar to Mo but less effective

Ti
Nb, Ta
Si
Affects detrimental effect for sensitization

Provides solid solution hardening
Provides precipitation of M23C6, M6C,
MC, etc., much precipitation of MC
decreases precipitation of g0 and g00
Austenitic stabilizer

N

Cu
B, Zr

Provides solid solution hardening
Provides precipitation of M6C

Suppress precipitation of Z phase
(Ni3Ti)
Provides oxidation resistance
Provides precipitation of g0
Provides precipitation of g0 and g00
Provides oxidation resistance

Al

C

Provides solid solution hardening
Provides precipitation of M23C6, as
benefit for notched rupture resistance
Provides solid solution hardening;
provides precipitation of M6C
Detrimental to
thermal stability
Deoxidizer in
melting process

Increases fluidity in
casting process
Mechanical
properties

Thermal stability
and mechanical
properties


Improves resistance to seawater

La, Ce

and titanium, and is hardened by the formation of
submicroscopic particles of intermetallic compounds,
Ni3(Ti, Al). The formation of intermetallic compounds occurs as a solid-state reaction during the
thermal aging (precipitation hardening) treatment.
Prior to the aging treatment, the alloy component
needs to be solution-annealed to dissolve any phases
that may have formed during previous processing.
The solution annealing and aging are normally carried out in the temperature range 980–1040  C and
540–590  C, respectively. Alloy K-500 has the excellent corrosion-resistant features of Alloy 400 with the
added benefits of increased strength up to 600  C and
hardness. The alloy has low magnetic permeability
and is nonmagnetic up to 134  C.
Some typical applications of Alloy K-500 include
pump shafts, impellers, medical blades and scrapers,
oil well drill collars and instruments, nonmagnetic

Increases creep rupture strength
Suppress precipitation of Z phase
Provides oxidation resistance

Deoxidizer in
melting process

housings and other complementary tools, electronic
components, springs, and valve trains.9
The mechanical and various physical properties of

nickel and typical nickel–copper alloys are shown in
Tables 4 and 5, respectively, along with those of
other nickel-based alloys. Physical properties at elevated temperature are shown in Tables 6–8.
2.08.2.1.2 Applications to nuclear power
industrial fields

Based on the high thermal conductivity (see Table 6)
and high corrosion resistance of nickel–copper alloys
in seawater, Alloy 400 has been widely applied in
boiler feed water heat exchanger tubes and shells,
and Alloy 500 has found wide use for pump shafts
and impellers in seawater pumps. Based on such
industrial applications, Alloy 400 was used for SG
tubes in some CANDU reactors.


Ni

Ni–Cr–Fe alloy

Ni–Cr–Fe/
Ni–Cr–Fe–Mo
P.H. alloy

Ni–Mo–Cr–Fe
alloy

Alloy 201

Ni > 99.0, C < 0.02


Low C commercial pure Ni. Applicable in caustic solution above 315 ЊC

Alloy 400

Ni–31Cu–2Fe (S £ 0.024)

Applicable to the components for sea water, salt unit, crude distillation, etc.

Alloy R-405

Ni–31Cu–2Fe–0.04S

Free machining grade of Alloy 400

Alloy K-500

Ni–30Cu–2Fe–0.6Ti–2.7Al

P.H. version of Alloy 400, up to 600 ЊC. Applicable to pump-shaft, impellers, scrapers, etc.

Alloy 600

Ni–15Cr–8Fe

Excellently resistant to in chloride SCC. Applicable to structural materials

Alloy 601

Ni–23Cr–8Fe–1.4Al


Excellently resistant to high-temperature oxidation. Applicable to oxidation-resistant parts

Alloy 690

Ni–29Cr–9Fe

Excellently resistant to many corrosive aqueous media, etc. Applicable to structural materials

Alloy 800

Fe–33Ni–21Cr

Highly resistant to high-temperature oxidation. Applicable to components for high-temperature use

Ni–15Cr–7Fe–2.5Ti–1Nb–0.7Al

Typical P.H. Ni-based alloy. Applicable to parts which need high tensile, creep and creep rupture properties

Ni–19Cr–17Fe–3Mo–0.9Ti–0.5Al–5.1Nb

Higher strength level than Alloy X-750. Applicable to parts which need high tensile, creep and creep rupture, etc.

Fe–25Ni–15Cr–1.3Mo–2.1Ti–0.3Al

Age-hardenable alloy. Good strength and oxidation resistance up to 700 ЊC

Alloy X-750
Alloy 718


Ni–28Mo–5Fe–2Co

Excellently resistant to hydrochloric acid. But, weak to solutions with mixing of oxidant

Alloy B-2

Alloy B

Ni–28Mo–4Fe–2Co–Low Si, Low C

Improved on corrosion resistance in heat affected zone after welding of Alloy B

Alloy B-3

Ni–30Mo–2Fe–2Co–2Cr–2W–2Mn

Minimized fabrication problems for Alloy B-2. Not applicable to the environment with ferric or cupric salt

Ni–17Mo–16.5Cr–4.5W–5.3Fe–0.3V

Excellent high resistance to oxidation, corrosion in chlorine, compounds with chlorine, oxidizing acid, etc.

Ni–16Mo–15.5Cr–5Fe–3.7W–2Co

Improved on fabricability and long range aging characteristics of Alloy C

Alloy C-4

Ni–16Mo–16Cr–2Fe–1.5Co


Advanced Alloy B. Superior corrosion resistance to oxidizing environment compared to Alloy B

Alloy C-22

Ni–21Cr–13.5Mo–4Fe–3W–2Co

Improved on corrosion resistance of Alloy C-276 in oxidizing environment

Alloy 625

Ni–21.5Cr–9Mo–4Fe

High creep rupture strength and high resistance to corrosion and pitting in oxidizing environment

Alloy 625LCF

Ni–21.5Cr–9Mo–4Fe

Improved on low cycle fatigue properties and cold formability of Alloy 625

Alloy C
Alloy C-276

Ni–Cr–Mo–Fe
alloy

Others

Features
Commercial pure Ni. Applicable in caustic solution below 315 ЊC


Alloy A286
Ni–Mo–Fe alloy

Chemical compositions
Ni > 99.0

Alloy 686

Ni–21Cr–16Mo–4Fe–3.7W–1.2Al

High Cr content of Alloy C-276. Excellent resistance to SCC, pitting and crevice corrosion in aggressive media

Alloy 59

Ni–23Cr–15.7Mo–1Fe–0.3Al

Pure Ni–Cr–Mo alloy. Excellent corrosion resistance and thermal stability

Alloy 825

42Ni–21.5Cr–25Fe–3Mo–2.2Cu–0.9Ti

Improved on aqueous corrosion resistance in a wide variety of corrosion media, modified by Alloy 800

Alloy G

Ni–22Cr–19.5Fe–6.5Mo–2Cu,Nb,Co–0.8W Superior corrosion resistance to oxidizing environment, inferior corrosion resistant to reducing environment

Alloy G-3


Ni–22Cr–19.5Fe–7Mo–2Cu–4Co

Improved on bending characteristics of weld joints for Alloy G

Alloy G-30

Ni–30Cr–15Fe–5Mo–2.7W–1.7Cu–4Co

Improved on corrosion resistance in wet phosphoric acid for Alloy G

Alloy N
Alloy 230
Alloy X
Alloy XR

Ni–16.5Mo–7Cr–4Fe

Excellent corrosion resistance to liquid fluoride

Ni–22Cr–14W–4Co–2Mo–2Fe

Excellent resistance to oxidation and nitriding, as well as high strength at high temperatures

Ni–22Cr–18.5Fe–9Mo–0.6W–2Co

High strength at high temperatures and good resistance to oxidation in high temperature air

Ni–Cr–Fe–Mo–2Co


Originally developed as a structural material for high temperature gas-cooled reactors

Figure 7 Nickel-based alloy systems and their features (dotted line: reference material, P.H.: precipitation hardened). In nuclear power plants, several of these nickel-based
alloys have been applied or are suitable as materials for various components, pipes, tubes, and other parts. The main applications or candidates of nickel-based alloys for
various nuclear reactors are summarized in Table 2.

Nickel Alloys: Properties and Characteristics

Ni–Cu alloy

Alloy no.
Alloy 200

240

Alloy system


Nickel Alloys: Properties and Characteristics

Table 2
Main applications or candidates of nickelbased alloys for nuclear reactors
Type of nuclear reactor

Alloys

BWR
PWR
CANDU reactor
LMFBR

HTGR

600, X-750, 718, 625
600, X-750, 718, 690, 800, A286
600, X-750, 718, 690, 800
X-750, 718, 800
600, X-750, 718, 625, XR

2.08.2.2

Ni–Cr–Fe and Ni–Cr–Fe–Mo Alloys

2.08.2.2.1 Chemical compositions, physical
properties, and mechanical properties

The chemical compositions of typical nickel–
chromium–iron
and
nickel–chromium–iron–
molybdenum alloys are shown in Table 3, together
with those of other nickel-based alloys.
As described earlier, nickel is a very versatile
corrosion-resistant metal. The addition of chromium
confers resistance to sulfur compounds and also provides resistance to oxidizing conditions at high temperatures or in corrosive solutions, with the
exceptions of nitric acid and chloride solutions. In
addition, chromium confers resistance to oxidation
and sulfidation at high temperatures.
Alloy 600 consists of about 76% nickel, 15%
chromium, and 8% iron. The alloy is not precipitationhardenable and can only be hardened and strengthened
by cold-working. It has excellent resistance to hot

halogen gases and has been used in processes involving chlorination. It has excellent resistance to oxidation and chloride SCC. It is widely applied as a
structural material in many industrial fields owing
to its strength and corrosion resistance.10
The thermal expansion coefficient of Alloy 600 is
smaller than those of austenitic stainless steels and
somewhat larger than those of ferritic steels, as shown
in Table 7. It is also highly resistant to sensitization in
heat-affected zones during welding. The alloy and its
weld metals such as Alloys 82, 132, and 182 have therefore been widely used for dissimilar metal weld joints
to reduce residual stresses and strains after welding.
Alloy 601 has a higher chromium content (about
23%) than Alloy 600 and about 1.4% aluminum. The
alloy is resistant to high-temperature oxidation and
has good resistance to aqueous corrosion. Oxidation
resistance is further enhanced by its aluminum content. The alloy has been applied to the muffles of
heat-treatment furnaces and in catalytic convertors
for exhaust gases in automobiles.11

241

Alloy X-750 contains titanium, aluminum, and
niobium, and is hardened by precipitation of the g0
phase as Ni3(Ti, Al, Nb).12 Alloy 718, on the other
hand, contains niobium, molybdenum, titanium, and
aluminum, and is hardened by the precipitation of
both the g0 phase as Ni3(Ti, Al, Nb) and the g00 phase
as Ni3Nb.13 These alloys were developed as high
creep-strength and high creep-rupture-strength
materials for jet-engine blades and vanes in the
1940s. These precipitation-hardened materials have

also been used in industrial gas-turbine materials. In
addition, Alloy X-750 has been used as a bolting
material and Alloy 718 has been applied to bellows,
springs, etc. for industrial products.
Alloy 690 (UNS N06690) was developed in the
late 1960s and has a higher chromium content (about
30%) than Alloys 600 and 601. It exhibits excellent
resistance to many corrosive aqueous media and
high-temperature atmospheres. The properties of
Alloy 690 are useful in a range of applications involving nitric or nitric/hydrofluoric acid production,
and as heating coils and tanks for nitric/hydrofluoric
solutions used in the pickling of stainless steels, for
example.14
Alloy 800 (UNS N08800) is an iron-based nickel–
chromium alloy. This alloy has been compared
to Alloys 600 and 690 from the view point of its
corrosion resistance in many environments. It was
introduced for industrial use in the 1950s as an
oxidation-resistant alloy and for high-temperature
applications requiring optimum creep and creeprupture properties. Alloy 800 has been widely used
as an oxidation-resistant material and is suitable for
high-temperature applications due to its high resistance to s-phase embrittlement after heating in the
range of 650–870  C.15
Alloy 825 (UNS N08825) was developed from alloy
800 by the addition of molybdenum (about 3%),
copper (about 2%), and titanium (about 0.9%) for
improved aqueous corrosion resistance in a wide variety of corrosive media. In this alloy, the nickel content
confers resistance to chloride-ion SCC. Nickel in conjunction with molybdenum and copper gives outstanding resistance to reducing environments such as those
containing sulfuric and phosphoric acids. Molybdenum also enhances its resistance to pitting and crevice
corrosion. In both reducing and oxidizing environments, the alloy resists general corrosion, pitting, crevice corrosion, intergranular (IG) corrosion, and SCC.

Some typical applications include various components
used in sulfuric acid pickling of steel and copper, components in petroleum refineries and petrochemical


242

Chemical compositions of nickel-based alloys

Alloy
Systems

Alloys

UNS
no.

Ni

200
201
400

Ni–Cu

Ni–Cr–Fe

Cr

Mo


Fe

N02200 ≧99.0a
N02201 ≧99.0a
N04400 ≧63.0a

–
–
–

–
–
–

≦0.40 –
≦0.40 –
≦2.50 –

R-405

N04405 ≧63.0

–

–

K-500

N05500 ≧63.0


–

600

N06600 ≧72.0

14.0–
17.0
14.0–
17.0
21.0–
25.0
27.0–
31.0
19.0–
23.0
14.0–
17.0
17.0–
21.0
13.50–
16.00
≦1.00

a

≧72.0

a


600M
601
690
Reference 800
Ni–Cr–Fe

X-750
718

Reference A286
Ni–Mo–Fe B

Ni–Mo–
Cr–Fe

Ni

N06601 58.0–
63.0
N06690 ≧58.0
N08800 30.0–
35.0
N07750 ≧70.0a
N07718 50.0–
55.0a
S66286 24.00–
27.00
N10001 b
b


B-2

N10665

B-3

N10675 ≧65.0

C-276

N10276

b

≦1.00
1.0–3.0
14.5–
16.5

Co

Mn

V

P

S

≦0.15 ≦0.35

≦0.020 ≦0.35
≦0.30 ≦0.50

–
–
–

≦0.35 –
≦0.35 –
≦2.0
–

–
–
–

≦2.50 –

≦0.30

≦0.50

–

≦2.0

–

–


–

≦2.0

–

≦0.25

≦0.50

–

≦1.50 –

–

–

6.0–
–
10.0
6.0–
–
10.0
b
13.0
–

≦0.15


≦0.50

–

≦1.0

–

–

≦0.010 ≦0.25 –
≦0.010 ≦0.25 –
≦0.0240 28.0– –
34.0
0.025–
28.0– –
0.060
34.0
≦0.010 27.0– 0.35–0.85
33.0
≦0.015 ≦0.50 –

≦0.05

≦0.50

–

≦1.0


–

–

≦0.015

≦0.10

≦0.50

–

≦1.0

–

–

≦0.15

≦0.50

–

≦1.0

–

≦0.10


≦1.0

–

–
–
–
–
–
2.80–
3.30
1.00–
1.50
26.0–
30.0
26.0–
30.0
27.0–
32.0
15.0–
17.0

W

7.0–
–
11.0
≧39.5 –

C


Si

Cu

Ti

Al

Nb
(þTa)

B

La

N

Zr

Nb

Ta

Niþ
Mo

–
–
–


–
–
–

–
–
–

–
–
–

–
–
–

–
–
–

–
–
–

–
–
–

–

–
–

–

–

–

–

–

–

–

–

–

2.30– –
3.15
–
–

–

–


–

–

–

–

–

–

–

–

–

–

–

–

≦0.50 –

–

–


–

–

–

–

–

≦0.015

≦1.0

–

–

–

–

–

–

≦0.015

≦0.50 –


1.0–
–
1.70
–
–

1.0– –
3.0
–
–

–

–

–

–

–

–

–

≦1.50 –

–

≦0.015


≦0.75 0.15–0.60

–

–

–

–

–

–

–

–

≦0.010

≦0.50 2.25–2.75

–

–

–

–


–

–

≦0.015 ≦0.015

≦0.30 0.65–1.15

–

–

–

–

–

–

–

–

–

–

–


–

–

–

–

–

–

–

–

–

–

–

–

≦0.080 ≦0.35

≦1.0

≦0.35 –


b

–

≦0.08

≦1.00

–

–

1.90–2.35

4.0–
6.0
≦2.0

–

≦0.05

≦1.0

≦2.5

–

–


–

0.70– –
1.20
4.75– ≦0.0060
5.50
–
0.0010–
0.010
–
–

–

≦0.02

≦0.10

≦1.0

≦2.00 0.10– ≦0.040 ≦0.030
0.50
≦1.0
0.2–
≦0.04 ≦0.03
0.4
≦1.0
–
≦0.04 ≦0.03


0.15–
0.60
0.40–
1.0
0.20–
0.80
≦0.35

–

–

–

–

–

–

–

–

1.0–
3.0
4.0–
7.0


≦3.0

≦0.010 ≦0.10

≦3.0

≦3.0

≦0.20 ≦0.030 ≦0.010

≦0.20 ≦0.20

≦0.50 –

–

–

–

3.0–
4.5

≦0.010 ≦0.08

≦2.5

≦1.0

≦0.35 ≦0.04


–

–

–

–

–

≦0.10 ≦0.20 ≦0.20 94.0–
98.0
–
–
–
–

5.0–
9.0
17.0b

–

≦0.080 ≦0.50

≦1.0

≦1.0


–

≦0.03

–

–

–

Nickel Alloys: Properties and Characteristics

Table 3


C-4
Ni–Cr–
Mo–Fe

C-22/
22
625

N06455

b

N06022

b


N06625 ≧58.0

625LCF N06626 ≧58.0
686
59
Reference 825
Others

G
G-3
G-30
N
230

XR

a

N06059

b

N08825 38.0–
46.0
N06007 b
N06985

b


N06030

b

N10003

b

N06230

b

N06002

b

b

20.0–
24.0
20.5–
23.0
20.5–
23.0

14.5–
17.0
12.5–
14.5
8.0–

10.0
8.0–
10.0
15.0–
17.0
15.0–
16.5
2.5–
3.5
5.5–
7.5
6.0–
8.0
4.0–
6.0
15.0–
18.0
1.0–
3.0
8.0–
10.0
8.0–
10.0

Includes cobalt.
As remainder P.H.: precipitation hardened.

b

≦3.0


–

≦0.015 ≦0.08

≦2.0

≦1.0

≦0.04

≦0.03

–

≦0.70

–

–

–

–

–

–

–


–

–

2.0–
6.0
≦5.0

2.5–
3.5
–

≦0.015 ≦0.08

≦2.5

≦0.50 ≦0.35 ≦0.02

≦0.02

–

–

–

–

–


–

–

–

–

–

–

≦0.10

≦1.0

≦0.50 –

≦0.015 ≦0.015

–

≦0.40

–

–

–


–

–

–

≦5.0

–

≦0.030 ≦0.020 ≦1.0

≦0.50 –

≦0.015 ≦0.015

–

≦0.40

–

≦0.020 –

–

–

–


≦5.0

3.0–
4.4
–

≦0.010 ≦0.08

–

≦0.75 –

≦0.04

–

0.02–0.25

≦0.40 3.15– –
4.15
≦0.40 3.15– –
4.15
–
–
–

–

–


–

–

–

–

≦0.010 ≦0.10

≦0.3

≦0.5

–

≦0.015 ≦0.005

≦0.05

≦0.5

–

≦1.0

–

–


≦0.03

≦1.0

≦0.05

≦1.0

≦2.5

–

≦0.04

≦0.03

≦1.5

≦0.015 ≦1.0

≦5.0

1.0–
2.0
≦1.0

–

≦0.04


≦0.03

≦0.8

≦5.0

≦1.5

–

≦0.04

≦0.02

≦1.00

≦0.20 ≦1.00 ≦0.50 ≦0.015 ≦0.020

≦1.5

≧22.0 –
18.0–
21.0
18.0–
21.0
13.0–
17.0
≦5.0


1.5–
≦0.03
4.0
≦0.50 0.04–
0.08
≦3.0
13.0– 0.05–
15.0
0.15
17.0– 0.20– 0.05–
20.0
1.0
0.15
17.0– 0.20– 0.07–
20.0
1.0
0.15

≦0.50

–

0.25– ≦5.0 0.30– –
0.75
1.00
≦1.0
0.5– ≦1.0
–
2.5
0.3–

≦1.0 0.6–
–
0.50
1.0

≦0.02

≦0.50 –
1.50–
3.0
1.5–
2.5
1.5–
2.5
1.0–
2.4
≦0.35

–

–

–

–

–

–


–

–

0.6–1.2

0.1–
0.4
≦0.2

–

–

–

–

–

–

–

–

–

–


–

–

–

–

–

–

–

–

1.75– –
2.5
≦0.50 –

–

–

–

–

–


–

–

–

0.30– –
1.50
–
≦0.010

–

–

–

–

–

–

–

–

–

–


–

–

–

–

–

–

–

–

–

–

–

–

–

–

–


–

–

Al þ Ti≦0.50

≦0.03

≦0.015

–

–

≦0.04

≦0.03

–

≦0.04

≦0.03

–

≦0.015

–


0.20– –
0.50
–
–

–

0.005–
0.050
–

≦0.03

≦0.10 –

≦0.008

–

Nickel Alloys: Properties and Characteristics

X

N06686

b

14.0–
18.0

20.0–
22.5
20.0–
23.0
20.0–
23.0
19.0–
23.0
22.0–
24.0
19.5–
23.5
21.0–
23.5
21.0–
23.5
28.0–
31.5
6.0–8.0

243


244

Nickel Alloys: Properties and Characteristics

Temperature (ЊC)
0


200

400

600

800

1000
700

100
90

600

Elongation
80

500

70
60

400

Stress (ksi)

50
300


40
Tensile strength

30

Stress (MPa)

Elongation (%)

110

2.08.2.2.2 Applications to nuclear power
industrial fields

200

20
100
10
0

Yield strength (0.2% offset)
0

400

800
1200
Temperature (ЊF)


0
2000

1600

Figure 8 High-temperature tensile properties of annealed
Alloy 200.

100
600

80
60

400
300

40
30

600

200

C)

15 Њ

ЊF (3


20

ЊC
800 ЊF (425

)

100
80

10
60

8
6

4

700

370

ЊF (

ЊC)
750

C)


00 Њ

ЊF (4

800

C)

25 Њ

ЊF (4

3

Stress (MPa)

Stress (ksi)

C)

45 Њ

ЊF (3

650

40
30

20


2
Nickel 201

10

1
0.01

and titanium. The alloy is age-hardenable to achieve
superior mechanical properties. It maintains good
strength and oxidation resistance at temperatures up
to about 700  C.16
The mechanical and physical properties of typical
nickel–chromium–iron and nickel–chromium–iron–
molybdenum alloys are shown in Tables 4 and 5,
respectively, together with those of other nickelbased alloys.

0.1
Minimum creep rate (% per 1000 h)

Figure 9 Typical creep strength of annealed Alloy 200.

plants (tanks, valves, pumps, agitators), equipment used
in the production of ammonium sulfate, pollution control equipment, oil and gas recovery, and acid
production.
Alloy A-286 (UNS S66286) is an iron-based
nickel–chromium alloy with added molybdenum

Alloys 600, 690, 800, X-750, and 718 have been used

as materials for components and parts of nuclear
power plants. These alloys are representative alloys
for nuclear power plant applications.
In the General Requirements of the first edition of
ASME Sec. III (1963) Rules for Nuclear Vessels, the
following terms are included. ‘‘The Code rules
do not cover deterioration which may occur in
service as a result of radiation effects, instability of
the material, or the effects of mechanical shock or
vibratory loading. These effects shall be taken into
account with a view to obtaining the design or the
specified life of the vessel. It is recommended that
the increase in the brittle fracture transition temperature due to neutron irradiation be checked
periodically by means of surveillance specimens.
The combined effects of fabrication, stress, and
integrated neutron flux should be considered.’’ Consequently, materials for the pressure boundary of
nuclear power plants are selected from those that
have been demonstrated to have excellent properties from experience.17
Alloy X-750 was selected as the bolting and coilspring material for water reactors (light and heavy
water reactors) based on practical experience with
the material in jet-engine applications as well as its
excellent creep resistance (i.e., excellent resistance
to stress relaxation). Wires and strips used for helical and flat springs are typically produced using
Alloy X-750. Table 9 shows an example of the design
stresses for springs at elevated temperatures.12
Alloy A286 was also selected as a bolting material
for water reactors based on similar reasons as those
described for Alloy X-750.
Alloy 718 was selected as a material for springs
and bellows for water reactors based on experience

with the material in jet engines as well as its excellent
creep resistance (i.e., excellent resistance to stress
relaxation), and its high yield strength in the temperature range of up to 400  C.


Table 4

Mechanical properties of nickel-based alloys
Alloys

UNS no.

Shape and treatment

Ultimate tensile
strength (MPa)

Yield strength
(0.2% offset)
(MPa)

Elongation (%)

ASTM

Ni

200
201
400

R-405
K500
600
600M
601
690

N02200
N02201
N04400
N04405
N05500
N06600

≧379
≧345
≧483
≧550
≧1100
≧552
≧586
≧552
≧586

≧103
≧83
≧193
≧240
≧790
≧241

≧241
≧207
≧241

≧40
≧40
≧35
≧40
≧25
≧30
≧30
≧30
≧30

B163
B163
B163
B164
B865
B163
B167
B163
B163

800
X-750

N08800
N07750


Seamless pipe and tube, annealed
Seamless pipe and tube, annealed
Seamless tube, annealed
Annealed
Rod and bar, precipitation hardened
Seamless tube, annealed
Seamless pipe, hot worked annealed
Seamless tube, solution-annealed
Seamless tube, cold drawn
(19.0 Â 1.65 mm)
Seamless tube, annealed
Bar, forge, precipitation hardened

≧517
≧1103

≧207
≧689

≧30
≧20

718
A286
B
B-2
B-3
C-276
C-4
C-22/22

625
625LCF
686
59
825

N07718
S66286
N10001
N10665
N10675
N10276
N06455
N06022
N06625
N06626
N06686
N06059
N08825

≧1275
≧895
≧690
≧760
≧760
≧690
≧690
≧690
≧827
971.5

≧690
≧690
≧586

≧1034
≧585
≧310
≧350
≧350
≧283
≧276
≧310
≧414
525
≧310
≧310
≧241

≧12
≧15
≧40
≧40
≧40
≧40
≧40
≧45
≧30.0
46.0
≧45
≧45

≧30

G
G-3
G-30
N
230
X
XR

N06007
N06985
N06030
N10003
N06230
N06002

Bar, forge, precipitation hardened
Bolting materials, hardening treated
Seamless pipe and tube, annealed
Seamless pipe and tube, annealed
Seamless pipe and tube, annealed
Plate, sheet, and strip
Plate, sheet, and strip
Plate, sheet, and strip
Plate, sheet, and strip, cold rolled
Plate, sheet, and strip, cold rolled
Seamless pipe and tube, annealed
Seamless pipe and tube, annealed
Seamless pipe and tube, cold worked

and annealed
Seamless pipe and tube, annealed
Seamless pipe and tube, annealed
Seamless pipe and tube, annealed
Plate, sheet, and strip
Seamless pipe and tube, annealed
Seamless pipe and tube, annealed
Seamless pipe and tube, annealed

B163
B637 N07752
Type1
B637
A453/A453M
B622
B622
B622
B575
B575
B575
B443
B443
B622
B622
B163, B423

≧621
≧621
≧586
≧690

≧760
≧690
≧639

≧241
≧241
≧241
≧280
≧310
≧276
≧220

≧35
≧40
≧30
≧40
≧40
≧35
≧40

Ni–Cu

Ni–Cr–Fe

Reference
Ni–Cr–Fe/Ni–Cr–Fe–Mo P.H.

Reference
Ni–Mo–Fe


Ni–Mo–Cr–Fe
Ni–Cr–Mo–Fe

Reference
Others

B622
B622
B622
B434
B622
B622

245

P.H.: precipitation hardened.

N06601
N06690

Nickel Alloys: Properties and Characteristics

Alloy systems


246

Table 5

Physical properties of nickel-based alloys

Alloys

UNS no.

Density
(g cmÀ3)

Melting
point ( C)

Coefficient of
thermal
expansion
to 100  C
(106  CÀ1)

Thermal
conductivity
at 100  C
(W mÀ1  C)

Specific heat
at 100  C
(J kgÀ1  C)

Electric
resistivity
at 100  C
(10À8 V m)


Young’s
modulus
at R.T.
(103 N mmÀ1)

Poisson’s
ratio at
R.T.

Shear
modulus
at R.T.
(GPa)

Ni

200
201
400
K-500
600
601
690
800
X-750

N02200
N02201
N04400
N05500

N06600
N06601
N06601
N08800
N07750

8.89
8.89
8.80
8.44
8.47
8.11
8.13
7.94
8.28

1435–1446
1435–1446
1300–1350
1315–1350
1354–1413
1360–1411
1343–1377
1357–1385
1393–1427

13.3
13.3
14.2
13.7

13.3
13.7
14.1
14.4
14.7

66.5
66.5
24
19.4
15.9
12.7
13.5
13
12.0

456
456
445
448
465
469
471
460
431

130
130
53.7
61.8

104
119
116
103
122

205
207
179
179
207
206
211
197
214

0.29
0.29
0.32
0.32
0.324
0.272
0.289
0.339

79.6
79.6

718
A286

B
B-2
B-3
C-276
C-4
C-22/22
625
625LCF
686
59
825
G
G-3
G-30
N
230
X

N07718
S66286
N10001
N10665
N10675
N10276
N06455
N06022
N06625
N06626
N06686
N06059

N08825
N06007
N06985
N06030
N10003
N06230
N06002

8.19
7.94
9.24a
9.22a
9.22a
8.87a
8.64a
8.69a
8.44
8.44
8.73a
8.6a
8.14
8.30
8.31
8.22
8.86
8.97a
8.23a

1260–1336
1370–1430


13.2
16.4
10.3
10.3
10.6
12.2
10.8
12.4
12.8
12.8
11.97
12.2
14.1
13.5
14.5
12.8
11.6
11.8
13.9

11.4
14.1
12.2
12.2
12.2
11.2
10.1
11.1
10.8

11.0
11.0
17.2
12.3
10.1
10.1
11.9
11.5
8.9
11.0

435
419
389
373
373
427
406
423
410
429
389
414
440

125
91.0
138
138
137

122
125
123
132
132
124.6
126
114

200
201
217
217
213
205
207
209
204
208
207
210
196
200

0.294

117
120
126
116


202
218
211
205

Ni–Cu
Ni–Cr–Fe

Reference
Ni–Cr–Fe/
Ni–Cr–Fe–
Mo P.H.
Reference
Ni–Mo–Fe

Ni–Mo–Cr–Fe
Ni–Cr–Mo–Fe

Reference
Others

a
After ASTM B622
P.H.: precipitation hardened.
R.T. is not defined (Room Temperature)

1370–1418
1325–1370
1351–1387

1290–1350
1290–1350
1338–1380
1310–1360
1370–1400
1260–1343
1343
1300–1400
1301–1371
1260–1355

80.8
80.8
79.3
73.4

0.307

79.0

0.278
0.28
0.34

81.4
77

0.29

76


0.34
0.33

78.8

456
419
419
461

Nickel Alloys: Properties and Characteristics

Alloy systems


Nickel Alloys: Properties and Characteristics

Table 6

247

Thermal conductivity (W mÀ1  C) of nickel-based alloys at elevated temperatures

Temperature ( C)

Alloy 200/201

Alloy 400


Alloy 600

Alloy 690

Alloy 800

Alloy C-22

Alloy A286

20
100
200
300
400
500
600
700
800
900
1000
1100

70.3
66.5
61.6
56.8
55.4
57.6
59.7

61.8
64.0
66.1
68.2
–

22.0
24.0
26.9
30.1
33.4
36.5
39.4
42.4
45.5
48.8
–
–

14.9
15.9
17.3
19.0
20.5
22.1
23.9
25.7
27.5
–
–

–

–
13.5
15.4
17.3
19.1
21.0
22.9
24.8
26.6
28.5
30.1
–

11.5
13.0
14.7
16.3
17.9
19.5
21.1
22.8
24.7
27.1
31.9
–

–
11.1

13.4
15.5
17.5
19.5
21.3
–
–
–
–
–

12.7
14.1
16.0
17.9
19.8
21.8
23.8
–
–
–
–
–

Table 7

Thermal expansion coefficient (Â10–6 mmÀ1  C) of nickel-based alloys at elevated temperatures

Temperature
( C)


Alloy
200/201

Alloy
400

Alloy
600

Alloy
690

Alloy
800

Alloy
C-22

Alloy
A286

316
stainless
steel

Carbon steel
(0.23C–0.64Mn–0.11Si)

20

100
200
300
400
500
600
700
800
900
1000
1100

–
13.3
13.9
14.2
14.8
15.3
15.5
15.8
16.2
16.6
16.9
17.1

14.2
15.2
15.7
16.1
16.3

16.6
17.0
17.4
17.7
18.1

10.4
13.3
13.8
14.2
14.5
14.9
15.3
15.8
16.1
16.4
–
–

–
14.06
14.31
14.53
14.80
15.19
15.70
16.18
16.60
17.01
17.41

17.79

–
14.4
15.9
16.2
16.5
16.8
17.1
17.5
18.0
–
–
–

12.4
12.4
12.4
12.6
13.3
13.9
14.6
15.3
15.8
16.2
–
–

–
16.4

16.5
16.9
17.2
17.5
17.7
17.7
–
–
–
–

–
16.0
–
16.2
–
17.5
–
18.6
20.0
–
–
–

–
12.2
–
13.1
–
13.9

–
14.9
–
–
–
–

Table 8

Specific heat (J kgÀ1  C) of nickel-based alloys at elevated temperatures

Temperature ( C)

Alloy 200/201

Alloy 400

Alloy 600

Alloy 690

Alloy 800

Alloy C-22

Alloy A286

20
100
200

300
400
500
600
700
800
900
1000
1100

427
445
459
470
–
–
–
–
–
–
–
–

427
445
459
470
–
–
–

–
–
–
–
–

444
465
486
502
519
536
578
595
611
628
–
–

450
471
497
525
551
578
604
631
658
684
711

738

460
–
–
–
–
–
–
–
–
–
–
–

–
423
444
460
476
485
514
–
–
–
–
–

419


In the case of austenitic stainless steels, SCC
has often been observed in environments that include
chlorides. However, high SCC resistance in chloride
solutions was observed for high nickel-content alloys
in the late 1950s, as indicated in Figure 10.5

To avoid SCC in chloride-containing environments, Alloy 600 was adopted as an SG tube material, based on experience with the material used
for SG tubes in the Connecticut Yankee reactor in
the late 1950s. Subsequently, Alloy 600 was used


248

Temper

Design stresses for springs at elevated temperatures
Method Thermal
of coiling treatment
( C hÀ1)

Maximum stress (MPa) for temperature ( C)
Up to 204–232 232–260 260–288 288–316 316–343 343–371 371–399 399–427 427–454 454–482 482–510 510–538 538–566 566–593 593–621 621–649

Helical springs
No.1
No.1 (9.7 cm)
Spring
Spring

Cold

Hot
Cold
Cold

732/16
483
732/16
70
649/4
689
55
1149/2 þ
843/24 þ
704/20

70
70
100
55

70
70
100
55

70
70
621
55


70
70
90
55

70
70
586
55

70
70
85
55

70
448–
–
55

–
379

Flat springs
No.1
Spring
Spring

–
–

–

100
120
70

100
120
70

100
758
70

100
110
70

100
724
70

100
100
70

100
–
70


100
–
70

Hot-finished

–

90

90

80

80

80

80

60

Hot-finished

–

704/16
100
704/16
827

70
1149/2 þ
843/24 þ
704/20
885/24 þ
90
704/20
60
1149/2 þ
843/24 þ
704/20

60

60

60

60

60

60

60

70
60–

414

55–
–
55

345
50–
–
55

310
45–
–
55

90

–

70

552
–
70

60

60

60


60

–

276
40–
–
55

70

60
–

172
172
–
50

–
–
–
50

–
–
–
40

–

–
–
30

–
–

–
–
50

–
–
40

–
–
30

70

70

70

60

60

60


–

–

–

–

60

60

60

–

–

–

–

Nickel Alloys: Properties and Characteristics

Table 9


Nickel Alloys: Properties and Characteristics


1000

crac
king

Cracking

Minim
um t
ime
to

Breaking time (h)

100

No cracking

10

Indicates commercial wire
Did not crack in 30 days

1

0

20

40

Nickel percent

60

80

Figure 10 Effect of increasing the nickel content on the
susceptibility of iron–18% chromium base wires in boiling
42% MgCl2.

Susceptibility to cracking

Transgranular

Intergranular

Chlorinated
water

Pure
water
10

A

Pure or
chlorinated
water

B


77

% Ni

Figure 11 Schematic diagram showing the influence of
nickel content on the cracking processes occurring in 18%
chromium austenitic alloys, when stressed slightly above
the yield point in 350  C water (demineralized or containing
1 g lÀ1 chloride ions).

worldwide for SG tubes for PWRs and for some
CANDU reactors.
Coriou reported as early as 1959 the possibility of
IG stress corrosion cracking (IGSCC) in hightemperature, high-purity water for high nickel-based
alloys, such as Alloys 600 and X-750, as shown in
Figures 11 and 12.18,19 However, this type of
IGSCC could not be reproduced by other researchers
for more than 15 years. Nevertheless, IGSCC was

249

eventually detected in SG tubes made of Alloy 600
in the Obrigheim reactor in 1972,20 and it was also
detected in support pins (split pins) and flexure pins
made of Alloy X-750 in the Mihama No. 3 reactor in
1978.21 Subsequently, IGSCC has been detected
in numerous SG tubes made from Alloy 600 and
support pins made of Alloy X-750. In addition, it was
detected in PWR reactor-vessel internal bolts made

of Alloy A286.
After these experiences, this type of IGSCC was
called ‘primary water stress corrosion cracking
(PWSCC)’; many studies of PWSCC have been carried out. As a result of these studies, thermally treated
(TT: heated at about 700  C for more than 10 h after
mill annealing) Alloy 600 was developed.22 The TT
Alloy 600 was used for SG tubes as an improved
IGSCC-resistant material from mill-annealed (MA)
Alloy 600, toward the end of the 1970s. TT Alloy 690
was developed for SG tubes in the early 1980s as a
material with excellent IGSCC resistance in PWR
primary water. The thermal treatment chosen for
TT Alloy 690 also consisted of heating at about
700  C for more than 10 h after mill annealing.23
This alloy has been and still is used for SG tubes
and control rod drive mechanism (CRDM) nozzles, etc.
in PWRs as an alternative material to MA Alloy 600.
In the case of conventional Alloy X-750, various
heat-treatment conditions have been specified for
different applications. In the case of support pins
and flexure pins for PWRs, only mechanical properties such as yield, tensile strength, or hardness were
specified for Alloy X-750 when used for bolts and
springs. Several different heat treatments were
selected by the suppliers of the material; the effects
of heat-treatment conditions on PWSCC resistance
are shown in Figure 13. Precipitation hardening
at about 715  C after solution annealing at a high
temperature near 1075  C (the so-called HTH condition) was selected for fabricating the most PWSCCresistant Alloy X-750.24 Alloy X-750 HTH has been
applied as a bolting material not only for PWRs but
also for BWRs due to its excellent IGSCC resistance

and high strength.25
However, the effects of heat treatment on IGSCC
resistance have not been so clearly delineated in
Alloys A-286 and 718. In particular, Alloy A-286
was replaced in many cases with Alloy X-750 HTH
as a bolting material.
Alloy 800 is an iron-based nickel–chromium
alloy. However, it has good IGSCC resistance in
high-temperature, high-purity water and caustic
solutions. A number of studies have been carried


Nickel Alloys: Properties and Characteristics

1.2

Contrainte appliquee ( ´ E 0.2

350 ЊC

)

250

1.0
0.8
0.6
0.4

200


1000
Duree avant rupture ou fissuration (heures)

10 000

Figure 12 Relationship between applied stress and 50% mean lifetime of the experimented specimens in 350  C water.

Temperature of solution heat treatment (ЊC)

1200
: No crack

: Crack [

: Double aged ]

1150

1100

1050

1000

950

900
675


700

750

800

850

Temperature of aging (ЊC)
(In case of double aging, the temperature of the first step aging)
Figure 13 Effect of heat-treatment condition on the stress corrosion cracking susceptibility of Alloy X-750 in
high-temperature water. (The alloys were cooled in water after solution heating.)

out to compare the IGSCC resistance of Alloys 800,
600, and 690, as shown in Figures 14 and 15.26 Alloy
800 was selected for SG tubes in some Germandesigned PWRs and CANDU-type reactors.
Alloy 600M is Alloy 600 with niobium addition.
The alloy was first developed for improved SCC
resistance in oxidizing high-temperature water environments of BWRs.27 This alloy has not been standardized yet but is specified in an ASME Code Case for
nuclear applications.28

2.08.2.3 Ni–Mo–Fe, Ni–Mo–Cr–Fe, and
Ni–Cr–Mo–Fe Alloys
2.08.2.3.1 Chemical compositions, physical
properties, and mechanical properties

The chemical compositions of typical nickel–
molybdenum–iron, nickel–molybdenum–chromium–
iron, and nickel–chromium–molybdenum–iron alloys
are shown in Table 3, along with those of other nickelbased alloys.



Nickel Alloys: Properties and Characteristics

251

350 ЊC WOL-type specimens
10

10
Alloy 600 MA–NaOH 100 g l-1
Alloy 600 MA–NaOH 4 g l-1

Alloy 600 HT–NaOH 100 g l-1

1

Alloy 600 HT–NaOH

4 g l-1

da
(μm h–1)
dt

da
(μm h–1)
dt

Alloy 690 MA–NaOH 100 g l-1

1

Alloy 690 HT–NaOH 100 g l-1
0.1

0.1
Alloy 690 MA–NaOH 4 g l-1

0

10

20

30

40

50

60

0

10

K1 (MPaÖm)

20


30

40

50

60

K1 (MPaÖm)

Figure 14 Stress corrosion tests in deaerated sodium hydroxide 350  C on fracture mechanics-type specimens:
comparison of Alloys 600 and 690 behavior effect of heat treatment at 700  C for 16 h.

10 000

(mg dm–2 day–1)

4000
Alloy 600 HT 16 h 700 ЊC

Corrosion rate

Minimum time for inducing a 500-μm crack (h)

Deaerated caustic soda
solution–350 ЊC
C-rings stressed to σ ∼
– ys
according to ASTM STP 425


3000
Alloy 800
Alloy 600 MA

2000

Boiling 10% HCl solution
6000

4000

2000

Alloy 690
Type 316
stainless
steel

1000

0

8000

0

0

5


10

15

20

25

30

35

Mo (%)

Figure 16 The effect of molybdenum content on
corrosion resistance of nickel–molybdenum alloys in boiling
10% hydrochloric acid solution.

1

4
10
40
100
NaOH concentration (g l−1)

500

Figure 15 Resistance to stress corrosion cracking of
Alloy 600 mill-annealed or heat-treated at 700  C, Alloy 690,

Alloy 800, and Type 316 stainless steel as function of
sodium hydroxide concentration at 350  C.

Nickel–molybdenum–iron alloys were originally
developed as hydrochloric acid-resistant materials.
They have superior resistance to reducing environments. Figure 16 shows the effect of molybdenum content in nickel–molybdenum alloys on

corrosion rates.29 It is seen that the corrosion rate
in 10% hydrochloric acid dramatically decreases
with increasing molybdenum content. Commercial
nickel–molybdenum alloys include about 30%
molybdenum.
Alloy B (UNS N10001) (nickel-based 28%
molybdenum–5% iron) is one of those rare materials
which is resistant to corrosion in hydrochloric acid up
to its boiling point. The alloy shows excellent corrosion resistance in reducing and oxidizing chloride
solutions. However, because of its lack of chromium


252

Nickel Alloys: Properties and Characteristics

content, care must be taken to avoid using this alloy
in oxidizing environments.
Alloy B-2 (UNS N10665) is an advanced version
of Alloy B. It has superior corrosion resistance in
weld-heat-affected zones compared to Alloy B, due
to reduced carbon and silicon contents and a
restricted range of iron content.

Alloy B-3 (UNS N10675) was developed to
minimize problems associated with the fabrication
of B-2 alloy components. Alloy B-3 has excellent
resistance to hydrochloric acid at all concentrations
and temperatures.30 It also withstands sulfuric,
acetic, formic, and phosphoric acids, as well as
other nonoxidizing media. Alloy B-3 has a special
chemistry designed to achieve a level of thermal
stability superior to that of Alloy B-2. It has been
applied to similar components as Alloy B-2, but
cannot be used in environments containing ferric
or cupric salts because these salts may cause rapid
corrosion failure.
Alloy C (UNS N10002) (nickel-based 18%
chromium–16% molybdenum–5% iron–4% tungsten)
is also an advanced version of Alloy B. It has superior
corrosion resistance to oxidizing environments compared to Alloy B due to the added chromium. However, Alloy C is degraded after heating in the
temperature range 650–1090  C due to the precipitation of M6C carbides and of m phase along grain
boundaries. Solution heat treatment is therefore necessary after welding in the case of this alloy.
Alloy C-276 (UNS N10276) improves upon this
weakness by using reduced carbon (<0.01%) and silicon (<0.08%) contents compared to Alloy C. The alloy
can be used in most cases in the as-welded state (without solution heat treatment after welding).31
Alloy C-4 (UNS N06455) improves upon the
long-range aging characteristics of Alloy C-276 by
the addition of titanium and a reduction in the iron
content.32
Alloy C-22 (same as Alloy 22) (UNS N06022)
shows improved corrosion resistance in oxidizing
environments due to increased chromium content
(about 22%) compared to Alloy C-276 and maintains

its corrosion resistance in reducing environments.33
Alloy 625 (UNS N06625) was originally developed as a gas-turbine material. It is a typical nickel–
chromium–molybdenum–iron alloy as well as a
solid-solution-hardenable alloy. It has high creeprupture strength at high temperatures, due to the
added molybdenum and niobium, and high resistance
to corrosion and pitting in oxidizing environments
such as nitric acid due to its higher chromium (about

22%) and lower molybdenum (about 9%) content
compared to Alloy C-276.34 However, the corrosion
resistance of the alloy in reducing environments such
as hydrochloric acid and sulfuric acid is inferior to
that of Alloy C-276. Alloy 625 is used where welding
is required, based on the stabilization of carbon by
niobium addition (about 3.5%) for preventing sensitization. Also, the alloy shows excellent SCC resistance to chloride solutions and seawater, due to its
high nickel content.
Alloy 625 LCF (UNS N06626), a modified Alloy
625, shows improved low-cycle fatigue properties
and cold formability for bellows applications.
Alloy 686 is very similar in composition to Alloy
C-276 but where the chromium level has been
increased from 16 to 21% while maintaining molybdenum and tungsten at similar levels. Alloy 686 is
used for resistance to aggressive media in chemical
processing, pollution control, pulp and paper manufacture, and waste management applications. This
alloy contains chromium, molybdenum, and a tungsten content of around 41%. To maintain its singlephase austenitic structure, this alloy has to be
solution-annealed at a high temperature of around
1220  C followed by rapid cooling to prevent precipitation of intermetallic phases.35
Alloy 59 has high chromium and molybdenum content with low iron content. This alloy has excellent
resistance to general corrosion, SCC, pitting, and crevice corrosion in aggressive corrosive environment. The
alloy is a nickel–chromium–molybdenum alloy without the addition of any other alloying element. This

purity and balance of nickel–chromium– molybdenum
is mainly responsible for its thermal stability.36
Alloy 825 (UNS N08825) was developed from
alloy 800 with the addition of molybdenum (about
3%), copper (about 2%), and titanium (about 0.9%)
for providing improved aqueous corrosion resistance
in a wide variety of corrosive media. In this alloy,
the nickel content confers resistance to chloride-ion
SCC. Nickel in conjunction with molybdenum and
copper gives outstanding resistance to reducing environments such as those containing sulfuric and phosphoric acids. Molybdenum also aids resistance to
pitting and crevice corrosion. In both reducing and
oxidizing environments, the alloy resists general corrosion, pitting, crevice corrosion, IG corrosion, and
SCC. Some typical applications include various components used in sulfuric acid pickling of steel and
copper, components in petroleum refineries and petrochemical plant (tanks, valves, pumps, agitators),
equipment used in the production of ammonium


Nickel Alloys: Properties and Characteristics

sulfate, pollution control equipment, oil and gas
recovery, and acid production.37
The mechanical and physical properties of typical
nickel–molybdenum–iron, nickel–molybdenum–
chromium–iron, and nickel–chromium–molybdenum–
iron alloys are shown in Tables 4 and 5 respectively,
along with those of other nickel-based alloys.
2.08.2.3.2 Applications to nuclear power
industrial fields

Alloy 625, as a typical nickel–chromium–

molybdenum–iron alloy, has been investigated for
its SCC resistance in high-temperature water as an
alternative material to austenitic stainless steels, from
the view point of preventing sensitization. The alloy
has also been studied for corrosion resistance in
highly caustic solutions as a candidate material for
components of supercritical light water-cooled reactors. Alloy 625 is one of the candidates for reactorcore and control-rod components in water-cooled
reactors and a candidate component material for
supercritical water-cooled reactors, due to its high
strength, excellent general corrosion resistance, SCC
resistance, and pitting resistance in high-temperature
water. The alloy is also being considered in advanced
high-temperature reactors because of its high allowable design stress at elevated temperatures, especially
between 650 and 760  C.
Alloy C-22 has been investigated for corrosion
resistance in highly caustic solutions and concentrated
chloride solutions as a candidate material for highlevel radioactive waste-disposal storage containers,
due to its excellent corrosion resistance in oxidizing
and reducing environments.
2.08.2.4

Other Ni-Based Alloys

2.08.2.4.1 Chemical compositions, physical
properties, and mechanical properties

The chemical compositions of other nickel-based
alloys not already described in the previously mentioned categories are shown in Table 3, along with
those of the alloys mentioned above.
Alloy G (UNS N06007) has excellent corrosion

resistance to hot sulfuric acid and hot phosphoric
acid. The alloy has superior corrosion resistance to
oxidizing environments compared to Alloy C-276,
due to its higher chromium content (about 22%)
than that of Alloy C-276 (about 18%). On the other
hand, Alloy G has inferior corrosion resistance to
reducing environments such as sulfuric acid compared to Alloy C-276, due to its lower molybdenum

253

content (about 6.5%) than that of Alloy C-276
(about 18%). A copper content of $2% is included
in Alloy G to improve its corrosion resistance in
sulfuric acid. Alloy G can be welded because of its
niobium content, which stabilizes carbon. However,
the alloy is highly susceptible to hot cracking during
welding.
Alloy G-3 (UNS N06985) is improved in terms of
the bending characteristics of welded joints due to a
reduced carbon and niobium content. This alloy has a
lower susceptibility to hot cracking during welding.
Alloy G-30 (UNS N06030) was originally developed to improve corrosion resistance in wet phosphoric
acid. This alloy shows excellent corrosion resistance to oxidizing acids, such as nitric acid, and also
to oxidizing halogen-ion-containing environments
such as nitric and fluoric acid, due to its increased
chromium content (about 30%).38
The chromium content in this alloy leads to deleterious effects in molten fluoride. However, Alloy N
shows excellent corrosion resistance to molten fluoride
due to its reduced chromium content (about 7%).39
Alloy 230 (UNS N06230) shows excellent resistance to oxidation and nitriding as well as high

strength at high temperatures. This alloy has been
applied as a heat-resistant material in industrial furnaces and gas turbines.40
Alloy X (UNS N06002) is a solid-solution-hardened
alloy owing to the presence of molybdenum. This
alloy has high strength at high temperatures and good
resistance to oxidation in high-temperature air.41
Alloy XR was originally developed as a structural
material for high-temperature gas-cooled reactors
(HTGR) and is a modified version of Alloy X. It is
produced by vacuum double melting with optimized
contents of manganese, silicon, and boron as intentional additives, while minimizing the aluminum,
titanium, and cobalt content, as these are undesirable
impurities.42
The mechanical and physical properties of the
above alloys are shown in Tables 4 and 5, respectively,
together with those of other nickel-based alloys.
2.08.2.4.2 Applications to nuclear power
industrial fields

Material development programs for HTGRs have
been promoted in several countries since the late
1960s, including tasks for developing and qualifying
materials such as nickel-based alloys for use as hightemperature structural materials. In the 1970s, the
state of the art for achievable maximum service temperature for structural materials was only 750  C for


254

Nickel Alloys: Properties and Characteristics


Alloy 800; thus, shifting the practical temperature
upward by about 200  C was a technical goal.
Alloy XR has been applied as a structural material
for the Japanese high-temperature engineering HTGR
test reactor (HTTR). This alloy has high resistance to
oxidation in high-temperature helium gas environments, and excellent creep-rupture strength up to
1000  C. In this alloy, the coexistence of appropriate
amounts of chromium and manganese helps to form a
Cr2MnO4 spinel layer on top of the Cr2O3 film, which
turns out to be quite stable and protective in heliumbased low-oxidizing environments, even during severe
thermal cycling. Figure 1743 illustrates the results of
long-duration corrosion tests during thermal cycling
for the original and improved versions of Alloy X.
An additional finding was that maintaining the boron
content in the range 30–50 ppm resulted in remarkable
improvement in the high-temperature strength of the
base metal and the performance of welded joints.
Alloy XR is suitable for use as a structural material
in ‘Generation IV Reactors.’ On the other hand, a
nickel–chromium–tungsten alloy is also currently
being investigated for similar applications as an
advanced version of Alloy XR.

2.08.3 Fabrication of Ni-Based Alloys
2.08.3.1

Melting

Squared depth of chromium depletion (10-5 mm2)


In the initial development stages, melting in air was
used to produce nickel–copper and nickel–chromium–
iron alloys. However, subsequent to the development

5
Simulated HTR coolant
T-cycled RT. ~ 1000 ЊC

4

Hastelloy X
3

2

1

0

Hastelloy XR

0

20 000
5000
10 000
15 000
Cumulative high temperature heating time (h)

Figure 17 Long-term exposure test results of a

nickel-based superalloy before and after improvement.

of Alloys X-750 and 718 as precipitation-hardened
high-strength materials for aerospace applications, a
vacuum melting process in addition to a double- or
triple-melting process has been applied to nickelbased alloys to minimize solidification segregation
and undesirable precipitation. The double- or triplemelting process is usually selected from vacuuminduction melting, electroslag remelting, and vacuum
arc remelting processes, as illustrated in Figure 18.44–51
The melting process in air was mainly applied to
mill-annealed Alloy 600 for SG tubes of PWRs until
the 1980s. However, after the experience with
IGSCC and other corrosion problems in the SG
tubes of PWRs, severe quality assurance for these
tubes was demanded by end users, and the melting
process was changed to vacuum melting and other
high-grade melting processes. Thus, TT Alloy 690
for SG tubes and other applications has been melted
using the vacuum oxygen decarburization process or
a double-melting process such as electroslag remelting after vacuum-induction melting.44
2.08.3.2

Hot Forming

Austenitic alloys have inferior hot-formability characteristics compared to low-alloy steels due to the
lack of softening at higher temperatures. Nickelbased alloys show even less formability than austenitic stainless steels due to their high deformation
resistance at higher temperatures.
Hot-forming is basically carried out in a temperature range between the solidus temperature and the
temperature at which recrystallization begins. However, nickel forms eutectic with various elements
including chromium, molybdenum, silicon, titanium,
aluminum, niobium, tungsten, phosphorus, sulfur,

and carbon. Thus, in the case of nickel-based alloys
that contain many alloying elements, heating at temperatures higher than 120  C poses the risk of local
fusion or precipitation of a secondary phase. Careful
selection of the hot-forming temperature range is
essential and the temperature range needs to be confirmed by high-temperature, high-speed tensile tests,
high-temperature torsion tests, forging tests, etc.,
prior to the hot-forming process.52 The Ugine–
Sejournet extrusion process with a glass lubricant is
normally applied during hot-working of tubes and
pipes, such as SG tubes. This is an expansion working
process using billets with machined and drilled holes
for the forged or rolled bloom.
Figure 19 illustrates the typical fabrication
process of hot-finished pipes for CRDM adapter


Nickel Alloys: Properties and Characteristics

VOD

255

Billet

Secondary
refining

Ingot casting

Soaking

Billet making
(hot rolling)

Ingot
ESR

VIM

Figure 18 Typical melting process of nickel-based super alloys. VOD; Vacuum Oxygen Decarburization, VIM; Vacuum
Induction Melting, ESR; Electro Slag Remelting.

VOD furnace

Ingot casting

Billet making

Billet

Machining

Hot finished
Hot extrusion
TT

Repeat

Pipes
for RPV
head

adapter

Mill anneal
SG
tubes
Cold drawing

Cold finished

Straightener

Figure 19 Typical fabricating process of piping and tubing. VOD; Vacuum Oxygen Decarburization, RPV; Reactor
Pressure Vessel.

nozzles of PWRs, compared to that of cold-finished
tubes for use as SG tubes.44,50
2.08.3.3

Cold Forming

Cold forming can be easily applied to nickel-based
alloys, except in the case of highly strengthened
alloys such as precipitation-hardened Alloys X-750,
718, etc. Under severe cold-forming conditions,

intermediate and final annealing steps are needed
for the products after cold forming.
The cold-forming process for the nickel–copper
Alloy 400 and for Alloys 600, 690, and 800 nickel–
chromium–iron alloys is typically as follows.

The bare tubes, which are hot-formed and heattreated, are pickled using nitric and fluoric acids to
remove glass and other contaminants incorporated
during the hot-working and other processes, and


256

Nickel Alloys: Properties and Characteristics

then finished to the desired shape by cold drawing, cold
reducing, or cold rolling at ambient temperature. This
cold-forming process produces small-diameter and
thin-walled tubes with excellent dimensional accuracy
and a fine surface finish that cannot be obtained by hot
processes. However, severe or progressive die-forming
operations require heavy-duty lubricants with good
surface-wetting characteristics and high film strength,
such as those found in metallic soaps and chlorinated
or sulfochlorinated oils. However, it is very important
to remove all traces of these lubricants prior to any heat
treatment or welding due to the danger of carbon
pickup and consequent lowering of corrosion resistance by the formation of complex carbides. Parts
formed using zinc-alloy dies should also be flashpickled to prevent liquid-metal embrittlement during
heating. In the case of the fabrication of Alloys TT600
and 690 for SG tubes and other nuclear products,
lubricant treatment using an oxalate film coating is
recommended for the tube-drawing process.52
The degree of work hardening is relatively large
for nickel-based alloys. However, these alloys have
somewhat higher strength and hence there is the

need to have forming equipment with sufficient
power commensurate with the mechanical characteristics of these alloys.
Cold drawing is a cold-forming procedure for bare
tubes using dies and subsequent drawing. There are
several cold-drawing methods, such as plug drawing,
sink drawing, mandrel drawing, and hydraulic drawing. Mandrel drawing and hydraulic drawing allow for
a high ratio of cold-working and fine surface finishes.
Cold rolling and cold reducing are applied during
tube fabrication using nickel-based alloys as one of
the cold-forming methods. Cold rolling can be used
for high-reduction-ratio cold forming, even for
nickel-based alloys with inferior workability characteristics, due to compressive forming.52
Figure 19 illustrates the typical fabrication process of cold-finished tubes for SG tubes, compared
with hot-finished pipes for CRDM adapter nozzles of
PWRs.44,50
2.08.3.4

Heat Treatment

Nickel and nickel alloys are susceptible to embrittlement by sulfur, phosphorus, lead, zinc, and some
other low-melting-point metals and alloys. These
materials may be present in lubricants, paints, marking crayons and inks, pickling liquids, dirt accumulated on the metal during storage, furnace slag and
cinder, or temperature-indicating sticks, pellets, and

lacquers. Any foreign substances, even those that are
nonembrittling, can burn into the surface of the metal
at high temperatures and cause difficulty during
subsequent processing. In addition, vapors produced
when these substances burn are usually objectionable
and can have an adverse effect on furnace and heating

fixtures. It is therefore extremely important that the
metal be clean before heating. Careful cleaning
results in real operating economy by preventing damage to the material in subsequent operations.53
Heat treatment is performed after hot-forming for
hot-finished products, or after cold forming for coldfinished products. An oil, gas, or electric furnace is
normally used for the heat treatment; however, a
bright-annealing furnace using hydrogen gas or
decomposition of ammonia gas is used for mill
annealing of seamless tubes made from nickel-based
alloys, for example, SG tubes of Alloys 600 and 690.
A vacuum-annealing furnace is used for thermal
treatment after mill annealing and polishing for TT
Alloys 600 and 690, to improve SCC and other corrosion resistance properties.
The heat-treatment conditions for nickel-based
alloys are selected according to the properties required.
In the case of Alloy X-750, equalizing at 885  C for
24 h, single-step aging or first-step aging at 710–735  C
followed by second-step aging at 600–650  C after
hot-forming, or solution annealing at 930–1030  C
has been applied to hot-rolled bars for bolting
materials. This type of heat treatment (the so-called
AH or BH condition) aims to produce high tensile
strength in the material for applications at <550  C,
due to precipitation hardening by the g0 phase. Another
type of heat treatment with a first-step aging at
800–850  C for 20–24 h and a second-step aging
at about 700  C after high-temperature solution
annealing at 1080–1160  C has been applied to creepresistant and creep-rupture-resistant materials at
temperatures operating higher than 550  C. This heat
treatment aims to yield a uniform matrix, enlarge the

grain size, recover any chromium-depleted zones, and
eliminate precipitate-free zones near grain boundaries.
However, the heat-treatment conditions of Alloy
X-750 are not suitable for SCC resistance in hightemperature water environments. The most suitable
heat-treatment condition in this case is single-step
aging at 700–730  C after solution heat treatment
at 1060–1100  C in order to precipitate semicontinuous M23C6 carbides along the grain boundaries.24
This heat treatment is specified in the American
Society for Testing and Materials (ASTM) standards
as B637 N07752 Type 1.


Nickel Alloys: Properties and Characteristics

In the case of Alloys 600 and 690, a thermal treatment has been applied after mill annealing to SG
tubes of PWRs and CANDU reactors and CRDM
nozzles of PWRs. The objective has been to improve
PWSCC resistance and IGSCC resistance in secondary side environments. The thermal treatment
includes heating at about 700  C for longer than 10 h.
2.08.3.5

Descaling and Pickling

Oxides, scales, tarnish films, or discoloration can be
removed chemically or mechanically. Chemical
treatment may consist of a molten caustic descaling
salt treatment followed by immersion in nitric–
hydrofluoric acid bath mixtures (20–25% nitric acid
plus 3–5% hydrofluoric acid) at 50–70  C. In the case
of Ni–Mo alloys, since these do not contain any

chromium, it is very important, indeed essential, not
to leave the material in the acid bath for more
than 60 s, followed immediately by a water rinse. If
sulfuric–hydrochloric acid baths are used, then this
precaution is not so critical for Ni–Mo alloys. Sand,
shot, or vapor blasting can be used for mechanical
descaling with proper care.53
2.08.3.6

Grinding and Machining

The machinability of nickel–molybdenum and
nickel–chromium–iron alloys is inferior to that of
austenitic stainless steels. When very close tolerances
are required for nickel-based alloys, grinding or
machining is the preferred method. Grinding wheels
must be selected carefully. Tungsten carbide and
ceramic-tipped tools are recommended for machining nickel-based alloys. High-speed steel tools can
also be used, although their machinability is not
very good. During machining, some nickel-based
alloys work-harden rapidly, generating large amounts
of heat during cutting, and may weld to the cuttingtool surface, thus offering high resistance to metal
removal due to their higher shear strength compared
to austenitic stainless steels.52
Sufficient power and rigidity of the machine,
avoiding vibration during machining, sharpness of
the tools, low cutting speeds, higher feed rates, and
a water-based cutting-oil lubricant should all be used
for machining nickel-based alloys.
2.08.3.7


Welding

For welding nickel-based alloys, cleanliness of the weld
joint is the most important parameter for producing a

257

sound weld. Lack of thorough cleaning has accounted
for most of the problems associated with welding
encountered in industry, including cracking, porosity,
and accelerated corrosion. The contaminants to watch
out for prior to welding are carbon, oxides, sulfur,
lead, phosphorous, and other elements that form lowmelting-point eutectics with nickel such as arsenic,
antimony, bismuth, and tin.54 These contaminants
may come from a variety of sources, including supplementary materials such as markers, tools, oils, etc.
For welding nickel-based alloys, matching filler
metals have been used. However, nickel has a thermal
expansion coefficient intermediate between that of austenitic stainless steels and low-alloy steels. Thus, nickel–
chromium–iron Alloys 82, 182, 132, 52, and 152 have
been used for dissimilar metal weld joints to minimize
the residual stress and strain in the weld joints.
Shielded metal arc welding (SMAW), metal inert
gas welding (MIG), submerged arc welding (SAW),
metal active gas welding (MAG), flux cored arc welding (FCAW), gas tungsten arc welding (GTAW), laser
beam welding (LBW), and electron beam welding
(EBW) have all been applied to nickel-based alloys.
Rods for SMAW and the flux for SAW must always
be used in a dry state during welding to avoid forming blow holes in the deposited weld metal. Filler
metals for GTAW, MIG, MAG, and FCAW must be

checked for contaminants such as stains, oils, paints,
etc. to avoid blow holes and hot cracking.
2.08.3.7.1 Weldability

Nickel-based alloys are relatively easy to weld, being
similar to austenitic stainless steels in that respect.
However, the hot-cracking susceptibility of nickelbased alloys is greater than that of austenitic stainless
steels and the fluidity of the melted metal is inferior
to that of both austenitic stainless steels and carbon
steels. It has been reported that the hot-cracking
susceptibility of nickel-based alloys is affected by
alloying elements such as niobium, titanium, and
aluminum and by minor elements such as sulfur,
silicon, manganese, phosphorus, etc., as shown in
Figures 20 and 21.55,56
2.08.3.7.2 Welding materials and example of
welding condition

Typical filler materials of nickel-based alloys for MIG
or MAG and weld materials of nickel-based alloys
for SMAW are summarized in Tables 10 and 11,
respectively. Typical welding conditions by automatic
gas tungsten arc welding used for some nickel-based
alloys are summarized in Table 12.57,58