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Publication No. SMC - 013
Copyright© 2003 by Special Metals Corporation
INCONEL®, INCOLOY®, MONEL®, INCO-WELD®, 625LCF ®, 725™,
800HT® and 925™ are trademarks of the Special Metals Corporation group
of companies.
The data contained in this publication is for informational purposes only and
may be revised at any time without prior notice. The data is believed to be
accurate and reliable, but Special Metals makes no representation or warranty
of any kind (express or implied) and assumes no liability with respect to the
accuracy or completeness of the information contained herein. Although the
data is believed to be representative of the product, the actual characteristics or
performance of the product may vary from what is shown in this publication.
Nothing contained in this publication should be construed as guaranteeing the
product for a particular use or application.
MANUFACTURING AND QUALITY CONTROLAn overview of the facilities and systems that make upthe world’s leading producer of corrosion- resistant alloys.
MATERIALS SELECTIONThe capabilities of the industry’s broadest selection of cor-rosion-resistant alloys.
EFFECTS OF WELL ENVIRONMENTSWhy nickel alloys are needed to resist corrosion inaggressive well fluids.
CORROSION TESTINGA compilation of corrosion data in environments rele-vant to oil and gas drilling and production.
Part 1:
Part 2:
Part 3:
Part 4:
C O R R O S I O N – R E S I S T A N T A L L O Y S F O R O I L A N D G A S P R O D U C T I O N
2
P A R T 1
INCONELfi Ni-Cr Alloys
INCONEL® Ni-Cr-Fe Alloys
INCONEL® Ni-Cr-Mo Alloys
INCOLOY® Fe-Ni-Cr Alloys
MONEL® Ni-Cu Alloys
INCO-WELD® Welding Products
The Special Metals Group of companies was created in 1998, when Special Metals Corporation
of New Hartford, New York acquired Inco Alloys International Inc., including its Huntington Alloys and Wiggin
Alloys divisions. With a history of alloy invention and production going back some 100 years, our new company
continues to provide solutions to your difficult materials problems through such time-tested products as our world-
recognized INCONEL®, INCOLOY® and MONEL® alloys.
Today’s Special Metals is a world leader in the invention, production and supply of the high-nickel, high-
performance alloys used for the “difficult jobs in engineering.” These alloys are highly engineered to offer a supe-
rior combination of heat resistance, high temperature corrosion resistance, toughness and strength and are used in
the world’s most technically demanding industries and applications. Special Metals offers the largest range of nick-
el-based alloys and product forms, as well as cobalt-based alloys, to more than 10 worldwide markets. We produce
nickel alloys in all standard mill forms, from large ingots and billets to plate, sheet, strip, tubing, bar and wire, the
latter of which includes core and filler wires for welding products. The company has manufacturing and research
facilities in the USA and Europe, sales offices in North America, Europe and Asia, and a distribution network
including most of the industrialized countries of the world.
Contact any of our offices listed on the last page of this publication or visit the SMC website,
www.specialmetals.com, for more information on our company and our products.
4
5
This two-high/four-high
reversing mill is used for pri-
mary breakdown of alloy
ingots. The mill has computer-
ized controls and can generate
up to 10 million pounds
(44MN) of separating force.
Computer-controlled extru-
sion presses produce seamless
tubulars of up to 10 in
(250mm) outside diameter.
5
4
Melting furnaces
include this vacuum-induction
furnace with its sophisticated
control system. Melting under
vacuum excludes contaminants
and produces alloys of precise
composition.
Electroslag remelting
enhances the structure and
purity of the metal. The opera-
tion is carried out under strict,
computerized control.
3
1 2+
2
3
6
M A N U F A C T U R I N G A N D Q U A L I T Y C O N T R O L
Natural gas continues to be one of the world’s most abundant
sources of energy. Increasingly, the recovery of new gas is
from deep formations that pose hostile environments for
downhole tubulars and other well components. In the past,
the selection of metallic materials for oil and gas wells was
a relatively straightforward proposition. Standard grades of
low-alloy and carbon steels were specified for drilling and
production tubulars with a few stainless steels and nickel
alloys in common use for special applications such as valves
and instrumentation. Today, materials selection for drilling
and completion of wells can be a complex task involving
high financial and safety risks. This situation is brought
about by several factors, including
1. deeper wells involving higher temperatures and pres-
sures,
2. enhanced recovery methods such as steam or CO2 injec-
tion,
3. increased weight considerations, especially offshore, and
4. the need for greater corrosion resistance in wells contain-
ing hydrogen sulfide (H2S), carbon dioxide (CO2), and
chlorides (Cl-).
Materials selection is especially critical for sour gas wells -
those containing H2S. Environments in sour wells are
extremely corrosive to metals, and H2S is highly toxic. In
some sour environments, corrosion can be controlled by
using inhibitors along with carbon steel tubulars. However,
inhibitors involve continuing high cost and may be unreli-
able, especially at higher temperatures. Adding corrosion
allowance to the tubing wall increases string weight and
reduces interior dimensions. In many cases, the preferred
alternative in terms of life-cycle economy and safety is the
use of a corrosion-resistant alloy (CRA) for tubulars and
other well components.
5
4
7
M A N U F A C T U R I N G A N D Q U A L I T Y C O N T R O L
A resistant alloy eliminates inhibitors, lowers weight,
improves safety, eliminates or minimizes workovers, and
reduces downtime.
For many decades, Special Metals has been the worldwide
leader in the development and application of corrosion-
resistant alloys, and the company is at the forefront in apply-
ing CRAtechnology to drilling and production of sour wells.
Before that involvement, Special Metals had been a long-
time supplier of nickel alloys for a range of corrosive or high
temperature applications in hydrocarbon and petrochemical
processing.
6
7
8
9
8
Ultrasonic (12) and
eddy-current (13) testing are
part of the stringent quality
control applied throughout pro-
duction.
Extruded tube shells
are cold worked to final size
on drawbenches or rotating-
die tube reducers.
Oil-country tubular
goods are produced in wide
ranges of diameters, wall
thicknesses and lengths.
Special Metals quality
control system includes exten-
sive laboratory facilities with
state-of-the-art equipment
such as scanning electron
microscopes (10) and atomic-
absorption spectrophotometers
(11).
6 7+
8 9+
10 11+
12 13+
13
10
11
129
M A N U F A C T U R I N G A N D Q U A L I T Y C O N T R O L
The MONEL, INCONEL and INCOLOY alloys invented
by the company have long service histories in such diverse
applications as drill collars, piping systems and valves, heat
exchangers, process vessels and pyrolysis furnaces.
Special Metals has manufacturing facilities and research
laboratories in the USA and the UK. The facilities are
unsurpassed in the production of high-performance alloys.
They are fully integrated for complete product control and
traceability from acquisition of raw materials through
melting, hot working, cold working and shipment of fin-
ished goods. Strict quality control is built into all process-
ing, a result of long experience in meeting the most strin-
gent of materials requirements in the aerospace and
nuclear industries. Impeccable material identification and
carefully maintained computer records enable complete
traceability of production history for many years.
The initial alloying and melting greatly influence quality,
and Special Metals has melting and remelting facilities
that span the range of modern technology. Included are
vacuum induction melting and air melting in conjunction
with argon-oxygen decarburization (A.O.D.). Vacuum
and electroslag remelting are used for even more precise
control of composition and microstructure.
Special Metals markets a range of alloys for sour-well
components. The product line constitutes the broadest
selection of CRA materials available from any supplier. It
is a single source for alloys that deliver high performance
in any known environment – from bottom hole, to well-
head, to processing plant. Included are alloys strengthened
by heat treatment as well as by cold work. Product forms
range from small-diameter tubing and
wire to 20,000 lb (9000 kg) ingots for large forged com-
ponents such as block master valves. A full selection of
matching and overmatching welding products are avail-
able.
Long lengths mean less
threading and fewer joints in
tubing strings.
14
10
The broad line of corrosion-resistant alloys produced by
Special Metals serves as a single source of materials for
applications ranging from bottom hole to flare stack.
P A R T 2
MATERIALS SELECTION
Above. The critical outer
portion of the Gullfaks A
flare boom is made of
INCONEL alloy 625.
Right. Submarine oil hose
for connection from super-
tankers to on-shore tank
farms in Saudi Arabia.
Connections are secured
with MONEL alloy 400
nuts and bolts.
12
M A T E R I A L S S E L E C T I O N
Selection of materials for downhole service in a sour
well is governed by a complex set of factors. Operating
temperatures can be as high as 800°C (1470°F). The hot
gas is corrosive, and the marine atmosphere presents its
own aggressive problems. High-temperature strength,
corrosion-resistance, ease of fabrication and readily
available welding products to match the base materials
are all important considerations. As in materials selection
for any application, the goal is to use a material that per-
forms successfully while providing optimum economy.
The material must provide the required physical and
mechanical properties while resisting the particular
environment of the well involved. And, expected
changes in the well environment over time, such as
increased chloride level, must also be considered.
Other important environmental factors to consider are
dissolved acid gases (CO2 and H2S) in the liquid phase,
chloride ions from salt or brine, temperature, and pres-
sure. In some formations, the presence of elemental sul-
fur is a further factor. The level of dissolved gases
depends on the partial pressure of each gas above the
liquid phase and on the temperature. Bottom-hole pres-
sure normally increases with depth, and bottom-hole
temperatures can be 500°F (260°C) or more in deep
wells.
Materials for downhole tubulars and other components
for oil and gas production span a wide range of grades
and compositions. As corrosion-resistance increases, so
too does the complexity of the material, from plain car-
bon steel to martensitic stainless steel (e.g., 13%
chromium steel), duplex (ferritic/austenitic) stainless
steel (e.g., 22% chromium/5% nickel), fully austenitic
stainless steel (e.g., 28% chromium/32% nickel), and
nickel alloys of various compositions. In nickel alloys
used for oil-country tubular goods, the levels of nickel,
chromium and molybdenum act as primary determi-
nants of corrosion-resistance.
Relatively small amounts of other elements including
copper, niobium, tungsten, aluminum and titanium may
have significant effects on corrosion-resistance or
strength.
Above. Special Metals supplies materials for the most severe sour well condi-
tions.
Below. Welding MONEL alloy 400 sheet onto steel riser pipes for an offshore
production platform. Used in the splash zone, the alloy is resistant to mussel
build-up. Operators report no difficulty in clearing other types of marine foul-
ing.
13
Right. An offshore block
master valve made of
INCOLOY alloy 925. The
valve body was forged from
a 20,000 lb (9000 kg) ingot.
INCOLOY alloy 925 was
selected for its strength and
corrosion- resistance dur-
ing normal service and for
its ability to meet fire-
resistance standards. The
alloy has the high-tempera-
ture strength and stability
to comply with API RP 6F,
Fire Test for Valves. Among
the requirements is the abil-
ity to withstand 2000°F
(1095°C) internal tempera-
tures with no leakage. (ABB
Vetco Gray, Inc.)
Above. 60 tonnes of
INCONEL alloy C-276
tubular product was speci-
fied for this sea-water
cooled, interstage and after
cooler fabricated by Hick
Hargreaves & Co. Ltd.,
Bolton, England, for
Marathon Oil U.K. Ltd.
These 15 m diameter ves-
sels are for use on the East
Brae gas condensate pro-
duction platform in the
North Sea, to support gas
recompressors capable of
delivering 9.6 million m3
per day at 350 bar pres-
sure.
14
M A T E R I A L S S E L E C T I O N
Above. INCOLOY alloy
800HT used for the top sec-
tion of a flare tower
for the Norne Field.
Shown here under assembly at
the Leirvik Sveis yard
on the island of Stord,
Norway.
Below. A drain caisson
(47 meters long, weighing 41
tonnes) for an offshore gas
platform, made of 26 mm dou-
ble-clad steel plate, with a 2
mm cladding of MONEL alloy
400 on either side of the steel.
ALLOYS FOR DOWNHOLE TUBULARS
Special Metals manufactures oil-country tubular goods
(OCTG) that withstand the most severe conditions in oil and
gas fields around the world. These highly alloyed materials
permit safe, economical production from reservoirs with
extremes of temperature, pressure, and H2S content.
INCONEL alloys C-276, G-3 and 050, and INCOLOY
alloys 825 and 028 are most often chosen for the optimum
combination of corrosion-resistance and economy. These
alloys, along with a wide selection of other corrosion-resist-
ant materials, are available in a variety of different forms for
downhole accessories and surface equipment. Plain-end
tubulars and coupling stock are produced in diameters, wall
thicknesses and yield strengths for most tubing and casing
requirements.
15
Above. A selection of valve
components for offshore
service, weld-overlaid with
INCONEL alloy 625. This
use of corrosion-resistant
alloy overlays on steel com-
ponents offers a cost-effec-
tive alternative to solid
alloy construction.
Right. INCOLOY alloy 925
fasteners, 4-16 mm diame-
ter, are used in “intelligent
pigs” for automated
pipeline inspection proce-
dures; particularly in areas
of high H2S which could
lead to sulfide stress crack-
ing in conventional steels.
M A T E R I A L S S E L E C T I O N
16
INCOLOY alloy 825, a nickel-iron-chromium alloy with
additions of 2.2% copper and 3.0% molybdenum, resists oxi-
dizing and reducing acids, chloride-ion stress-corrosion
cracking, pitting and intergranular corrosion. The molybde-
num addition is especially effective in increasing an alloy’s
resistance to sour well environments. INCOLOY alloy 825
is a solid- solution alloy (not strengthened by heat treatment)
that can be strengthened by cold work to minimum yield
strengths (0.2% offset) up to 125,000 psi
(862 MPa). INCOLOY alloy 825 could be considered for
service in well environments where stainless steels would be
susceptible to chloride stress cracking, pitting, or crevice
corrosion. Depending on specific strength level and temper-
ature, the alloy has been shown to be resistant to stress-cor-
rosion cracking at H2S partial pressures up to about
1000 psi (7 MPa). The usual maximum service temperature
is about 350°F (175° C).
INCONEL alloy G-3, a nickel-chromium-iron alloy with
additions of 2.0% copper and 7.0% molybdenum, is similar
to INCOLOY alloy 825 in nickel and chromium contents,
but has approximately double the molybdenum. INCONEL
alloy G-3 is a solid-solution alloy that can be cold worked
to minimum yield strengths (0.2% offset) up to 130,000 psi
(900 MPa). With its higher molybdenum, INCONEL alloy
G-3 offers greater resistance to sour environments than
INCOLOY alloy 825.
Below. INCOLOY alloy 925
completion tubing, 8.5 in (216
mm) diameter, 0.75 in (19
mm) wall, 110 ksi
(758 MPa) yield strength.
Available in lengths up to 30
ft (9.14 m).
Above. MONEL alloys 400
and K-500 are used in well-
head hardware, pumps and
valves.
17
M A T E R I A L S S E L E C T I O N
Right. An Otis Versa-Trieve®
production packer for use in
intermediate pressure wells,
and extensively used in sand
control applications.
Internal, flow-wetted compo-
nents, such as the main man-
drel, have been made of
INCOLOY alloy 925.
Far Right. Otis SP-1 non-
elastomer, flapper-type,
tubing-retrievable sub-sur-
face safety valves are used
to shut off the flow of oil or
gas from the producing tub-
ing string. These surface
controlled valves have been
made with components of
INCOLOY alloy 925.
Depending on such factors as strength level, temperature,
and presence of free sulfur, INCONEL alloy G-3 is resistant
to cracking at H2S partial pressures up to about 2500 psi (17
MPa). In the upper regions of H2S content, service tempera-
ture would be limited to about 350°F (175°C) although high-
er temperatures are possible at lower H2S levels.
INCONEL alloy C-276, a nickel-molybdenum-chromium
alloy with additions of iron (6%) and tungsten (4%), is used
in the most severe sour well environments including those
having free sulfur. Its molybdenum content of 16% is the
highest commercially available in oil-country tubular
goods, offering the maximum resistance to environments
containing H2S. The solid-solution alloy can be cold
worked to high strength levels and is available with mini-
mum yield strength (0.2% offset) of 150,000 psi (1034
MPa). Depending on the combination of specific yield
strength, temperature, and free-sulfur presence, lNCONEL
alloy C-276 is resistant to cracking at H2S partial pressures
up to about 10,000 psi (70 MPa). The alloy has shown
resistance to sour environments at temperatures up to 500°F
(260°C).
ALLOYS FOR DOWNHOLE ACCESSORIES AND SUR-
FACE EQUIPMENT
The many different downhole components - hangers, valves,
pumps, packers, wirelines, mandrels, screens, landing nip-
ples, etc - needed to complete and produce a well face the
same environment as the tubing string. Although some com-
ponents may be under lower stress or have less critical func-
tions, all downhole hardware in a sour well must have ade-
quate resistance to the environment. The same alloys
used for tubulars are also used for other downhole compo-
nents. In many cases, however, a different alloy is more
appropriate for reasons of specialized properties, economy,
or ease of fabrication.
18
Left. Fasteners of various
nickel alloys provide
strength and corrosion-
resistance in critical oil-
field connections
Below. MONEL alloys 400,
R-405 and K-500 are stan-
dard materials for valves,
valve actuators and pumps
in oil field and processing
applications.
19
Left. A single point mooring
buoy where the mating sur-
faces of the universal joint
are overlaid with
INCONEL alloy 625 for
resistance to stress-corro-
sion cracking and crevice
corrosion.
Below. An onshore terminal
where LPG is compressed
and cooled from 133 to
26°C in batteries of air-
cooled INCOLOY alloy 825
heat exchangers set 25
meters high in piperacks
where wind speeds can
exceed 120 mph.
Below. INCOLOY alloy 25-6MO was used to fabricate this desalination unit for an
offshore platform. The unit was fabricated by KGD Industrial Services Ltd.
(Hereford, England) for Alfa Laval Desalt (Copenhagen, Denmark)
20
For example, high strength is obtained in tubulars by cold
working, but parts of heavy or non-uniform cross section
cannot be strengthened by cold working. Such components
need to be made of an alloy that can be strengthened by a
precipitation hardening (age hardening) heat treatment.
Special Metals markets the broadest range of corrosion-
resistant alloys in the industry. All are produced to the high
standards of quality and performance applied to CRA tubing
and casing, and are manufactured in a full range of standard
mill forms including pipe, tubing, rounds, flats, hexagons,
wire, plate, sheet, strip, and forging stock. From this exten-
sive product line the best alloy can be selected in the required
form for virtually any downhole or wellhead component.
• MONEL alloy 400, a solid-solution nickel-copper alloy
with moderate strength and high corrosion- resistance, is
especially resistant to sea water and brines.
• MONEL alloy R-405 is a free-machining version of
MONEL alloy 400.
• MONEL alloy K-500 is a high-strength, age-hardenable
version of MONEL alloy 400.
• INCONEL alloy 600 is a solid-solution nickel- chromium
alloy with good strength and resistance to general corrosion
in a variety of environments.
• INCONEL alloy 625, a solid-solution nickel- chromium-
molybdenum-niobium alloy, has high strength and out-
standing resistance to general corrosion, pitting, crevice
corrosion, and stress-corrosion cracking.
• INCONEL alloy 718, an age-hardenable nickel-chromi-
um-iron alloy containing significant amounts of niobium,
molybdenum, titanium, and aluminum, combines good
corrosion-resistance with extremely high strength.
• INCONEL alloy 725, an age-hardenable nickel-chromi-
um-molybdenum-niobium alloy, combines the excellent
corrosion-resistance of INCONEL alloy 625, including
resistance to the effects of H2S, with high strength obtained
by heat treatment instead of cold work.
• INCONEL alloy 725HS, a high-strength version of
INCONEL alloy 725.
• INCONEL alloy X-750 is a nickel-chromium alloy similar
to INCONEL alloy 600 but made age-hardenable by addi-
tions of aluminum and titanium for higher strength in addi-
tion to corrosion resistance.
• INCONEL alloy 050, an alloy with excellent resistance to
stress-corrosion cracking, particularly in sour gas environ-
ments, used for downhole tubing in oil and gas extraction.
• INCOLOY alloy 800 is a solid-solution nickel-iron-
chromium alloy with good strength and resistance to gen-
eral corrosion in many environments. It is also available as
INCOLOY alloys 800H and 800HT for higher strength at
temperatures over 1100°F (590°C).
• INCOLOY alloy 925, an age-hardenable nickel-iron-
chromium-molybdenum-copper alloy, has the corrosion-
resistance of INCOLOY alloy 825 along with high
strength achieved by heat treatment. The alloy was devel-
oped especially for sour-well components that cannot be
strengthened by cold working.
• INCOLOY alloy 25-6MO, a solid-solution nickel-iron-
chromium alloy with a substantial (6%) addition of molyb-
denum, is especially useful to resist pitting and crevice cor-
rosion in media containing chlorides, such as sea water.
• INCOLOY alloy 27-MO, a solid-solution nickel-iron-
chromium alloy with a substantial (7%) addition of
molybdenum, is a higher alloyed version of INCOLOY
alloy 25-6 MO.
• INCOLOY alloy 028, a corrosion-resistant austenitic
stainless steel used for downhole tubing in oil and gas
extraction operations.
M A T E R I A L S S E L E C T I O N
21
WHERE THE ENVIRONMENT IS AGGRESSIVELY CORROSIVE
For These Components Specify These Proven Alloys
Bellows expansion INCOLOY alloy 825joints MONEL alloy 400
INCONEL alloys 625, 625LCF & X-750
Downhole tubing, casing INCOLOY alloys 825 & 028and couplings INCONEL alloys C-276, G-3 & 050
Drill collars MONEL alloy K-500
Drill pipe INCOLOY alloy 825
Fasteners INCOLOY alloy 925MONEL alloy K-500INCONEL alloys 725,725HS, 686,& X-750
Fittings INCOLOY alloy 825 INCONEL alloy 625
Filters and separators MONEL alloy K-500 INCOLOY alloys 825 & 27-7 MO
Flare booms INCONEL alloy 625
Flare stack tips INCOLOY alloys 800HT & DS
Hangers INCOLOY alloy 925INCONEL alloys 725, 725HS, & 718
Heat exchangers INCOLOY alloys 825, 800HT, 27-7MO, & 25-6MOINCONEL alloy 625MONEL alloy 400
Instrumentation tubing INCOLOY alloy 825MONEL alloy 400INCONEL alloy 625
Landing nipples INCONEL alloy 725 & 725HSINCOLOY alloy 925
Packers INCOLOY alloy 925 INCONEL alloys 718, 725, & 725HS
Polished-bore receptacles INCONEL alloys 718 & 725(PBRs) INCOLOY alloy 925
Pumps INCOLOY alloy 925INCONEL alloy 718MONEL alloys 400, R-405 & K-500
Rig leg cladding MONEL alloy 400
Riser pipe cladding MONEL alloy 400 INCOLOY alloy 825
Sea-water piping MONEL alloy 400INCONEL alloy 625INCOLOY alloys 825, 25-6MO, & 27-7 MO
Side-pocket mandrels INCONEL alloy 725INCOLOY alloy 925
Springs INCONEL alloys X-750 & 725
Sucker rods INCONEL alloy 718MONEL alloys 400 & K-500
Tool joints INCOLOY alloy 925MONEL alloy K-500
Tubing calipers MONEL alloys 400 & K-500
Valves INCOLOY alloys 825 & 925INCONEL alloys 625, 718 & 725MONEL alloys 400, R-405 & K-500
Wire lines INCOLOY alloys 825, 25-6 MO, & 27-7 MO
M A T E R I A L S S E L E C T I O N
Flattening tests can be used to evaluate the quality of downhole tubulars.
MONEL MONEL MONEL INCONEL INCONELElement alloy 400 alloy R-405 alloy K-500 alloy 600 alloy 625
UNS N04400 UNS N04405 UNS N05500 UNS N06600 UNS N06625
Nickel 63.0 min 63.0 min 63.0 min 72.0 min 58.0 min
Chromium – – – 14.9-17.0 20.0-23.0
Iron 2.5 2.5 2.0 6.0-10.0 5.0
Copper 28.0-34.0 28.0-34.0 27.0-33.0 0.5 –
Molybdenum – – – – 8.0-10.0
Niobium – – – – 3.15-4.15
Aluminum – – 2.30-3.15 – 0.40
Titanium – – 0.35-0.85 – 0.40
Sulfur 0.024 0.025-0.060 0.01 0.015 0.015
Tungsten – – – – –
Cobalt – – – – 1.0
Carbon 0.3 0.3 0.25 0.15 0.10
Manganese 2.0 2.0 1.5 1.0 0.50
Silicon 0.5 0.5 0.5 0.5 0.50
Phosphorus – – – – 0.015
Boron – – – – –
Vanadium – – – – –
Nitrogen – – – – –
* single values are maximum quantities except as indicated
CHEMICAL COMPOSITIONS, %*, OF NICKEL ALLOYSFOR OIL-COUNTRY APPLICATIONS (cont. p.21)
50.0-55.0
17.0-21.0
18.5 nom
0.30
2.80-3.30
4.75-5.50
0.20-0.80
0.65-1.15
0.015
–
1.0
0.08
0.35
0.35
0.015
0.006
–
–
55.0-59.0
19.0-22.5
9 nom
–
7.0-9.5
2.75-4.0
0.35
1.0-1.7
0.010
–
–
0.03
0.35
0.20
0.015
–
–
–
44 nom
21.0-23.5
18.0-21.0
1.5-2.5
6.0-8.0
0.50
–
–
0.03
1.5
5.0
0.015
1.0
1.0
0.04
–
–
–
57 nom
14.5-16.5
4.0-7.0
–
15.0-17.0
–
–
–
0.03
3.0-4.5
2.5
0.01
1.0
0.08
0.04
–
0.35
–
70.0 min
14.0-17.0
5.0-9.0
0.50
–
0.70-1.20
0.40-1.00
2.25-2.75
0.01
–
1.0
0.08
1.0
0.50
–
–
–
–
50.0 min
19.0-21.0
–
0.5 max
8.0-10.0
–
–
–
0.03
0.4
–
.02 max
1.0 max
1.0 max
.03 max
–
–
–
24.0-26.0
19.0-21.0
46 nom
0.8-1.5
6.0-7.0
–
–
–
0.03
–
–
0.02
1.0
0.05
0.045
–
–
0.10-0.20
26.0-28.0
20.5-23.0
Balance
0.5-1.5
6.5-8.0
–
–
–
0.01
–
–
0.020
3.00
0.5
0.03
–
–
0.3-0.4
30.0-34.0
26.0-28.0
–
0.6-1.4
3.0-4.0
–
–
–
0.03
–
–
.03 max
2.5 max
1.0 max
.03 max
–
–
–
30.0-35.0
19.0-23.0
39.5 min
0.75
–
–
0.15-0.60
0.15-0.60
0.0015
–
–
1.10
1.5
1.0
–
–
–
–
38.0-46.0
19.5-23.5
22.0 min
1.5-3.0
2.5-3.5
–
0.2
0.6-1.2
0.03
–
–
0.05
1.0
0.5
–
–
–
–
42.0-46.0
19.5-22.5
22.0 min
1.5-3.0
2.5-3.5
0.5
0.1-0.5
1.9-2.3
0.03
–
–
0.03
1.0
0.5
0.03
–
–
–
PHYSICAL PROPERTIESa OF NICKEL ALLOYS FOR OIL-COUNTRY APPLICATIONS
Young’s Coefficient Thermal ElectricalDensity Modulus Specific Heat of Expansionc Conductivity Resistivity
Magnetic Btu/ J/ 10-6/ 10-6/ Btu.in/ W/m. ohm.Alloy lb/in3 g/cm3 106psi GPa Permeabilityb lb.ºF kg.ºC ºF ºC ft2.h.ºF ºC cmil/ft µohm•m
MONEL alloy 400 0.318 8.80 26.0 179 –d 0.102 427 8.8 15.8 151 21.8 329 0.547
MONEL alloy R-405 0.318 8.80 26.0 179 –d 0.102 427 8.7 15.7 151 21.8 307 0.510
MONEL alloy K-500 0.305 8.44 26.0 179 1.002 0.100 419 8.3 14.9 121 17.5 370 0.615
INCONEL alloy 600 0.306 8.47 31.1 221 1.010 0.106 444 7.9 14.2 103 14.9 620 1.03
INCONEL alloy 625 0.305 8.44 30.1 208 1.0006 0.098 410 7.4 13.3 68 9.8 776 1.29
INCONEL alloy 718 0.296 8.19 29.0 200 1.0011 0.104 435 8.0 14.4 79 11.4 751 1.25
INCONEL alloy 725 0.300 8.30 29.6 204 <1.001 – – 7.5 13.0 – – 688 1.14
INCONEL alloy 725HS 0.300 8.30 29.6 204 <1.001 – – 7.5 13.0 – – 688 1.14
INCONEL alloy X-750 0.299 8.28 31.0 214 1.0035 0.103 431 7.5 13.5 83 12.0 731 1.22
INCONEL alloy G-3 0.294 8.14 28.9 199 – 0.108 452 8.1 14.6 69 10.0 – –
INCONEL alloy C-276 0.321 8.89 29.8 205 1.0002 0.102 427 7.2 13.0 68 9.8 739 1.23
INCONEL alloy 050 0.303 8.39 27.9 192 – – – 7.5 13.5 – – – –
INCOLOY alloy 27-7 MO 0.289 8.02 27.7 191 1.004 0.109 454 8.8 15.8 70 10 604 1.00
INCOLOY alloy 25-6MO 0.290 8.03 27.6 190 1.005 0.12 500 9.9e 17.8e 116 16.7 480 0.80
INCOLOY alloy 028 0.290 8.03 29.0 200 – 0.11 460 8.3 14.9 79 11.4 560 0.93
INCOLOY alloy 800 0.287 7.94 28.5 197 1.014 0.11 460 9.0 16.2 80 11.5 595 0.989
INCOLOY alloy 825 0.294 8.14 29.8 205 1.005 0.105 440 8.5 15.3 77 11.1 678 1.13
INCOLOY alloy 925 0.292 8.08 29.2 201 1.001 0.104 435 8.2 14.8 – – 701 1.17a Room-temperature values except for thermal expansion.b H=200 oersted (15.9kA/m).c Between room temperature and 600ºF (315ºC).d May be ferromagnetic at room temperature; Curie temperature varies from slightly below to somewhat over room temperature.e Between room temperature and 750ºF (400ºC).
INCONELalloy 718
UNS N07718
INCONELalloy
725/725HSUNS N07725
INCONELalloy G-3
UNS N06985
INCONELalloy C-276
UNS N10276
INCONELalloy X-750UNS N07750
INCONELalloy 050
UNS N06950
INCONELalloy
25-6 MOUNS N08925
INCONELalloy
27-7 MOUNS S31277
INCONELalloy 028
UNS No8028
INCONELalloy 800
UNS N08800
INCONELalloy 825
UNS N08825
INCONELalloy 925
UNS N09925
CHEMICAL COMPOSITIONS, %, OF NICKEL ALLOYS FOR OIL-COUNTRY APPLICATIONS (continued)
23
Right. 7-inch (178 mm)
diameter INCOLOY alloy
825 threaded tubing for the
Phase 2 downhole require-
ments of the QATARGAS
project. (Grant Prideco,
Inc., Houston)
Below. The QATARGAS
project, in the Persian Gulf,
is probably the largest
investment in energy out of
the Middle East. INCONEL
alloy 625 was specified for
Phase 1 piping systems at
the wellheads, on the utility
processing platform, and for
inter-platform systems car-
ried by bridges. INCOLOY
alloy 825 tubing was speci-
fied for Phase 2 for its
proven track record as a
downhole tubular product in
oil and gas fields world-
wide.
24
TYPICAL MECHANICAL PROPERTIES FOR OIL COUNTRY TUBULAR GOODS
Hardness,
Alloy
Yield Strength* Tensile Strength* Elongation Rockwell**
Max. for sour wellksi MPa ksi MPa % service
INCONEL alloy G-3 125 862 130 896 13 C39 max.
INCONEL alloy C-276 125 862 130 896 13 C45 max.
INCONEL alloy 050 125 862 130 896 13 C38 max.
INCOLOY alloy 028 110 758 130 896 15 C33 max.
INCOLOY alloy 825 110 758 130 896 16 C35 max.
INCOLOY alloy 925 110 758 140 965 18 C38 max.
*Other strength levels available on request. **Condition and hardness limitations as stipulated by NACE MR0175.
TYPICAL MECHANICAL PROPERTIES FOR AGE-HARDENED CORROSION-RESISTANT ALLOY BAR
AlloyYield Strength Tensile Strength Elongation Hardness*
ksi MPa ksi MPa % Rockwell
MONEL alloy K-500 95 655 130 896 20 C35
INCONEL alloy 718 120 827 150 1034 20 C40
INCONEL alloy 725 120 827 150 1034 20 C40
INCONEL alloy 725HS 149 1029 199 1372 22 C43
INCONEL alloy X-750 110 758 165 1138 20 C35
INCOLOY alloy 925 110 758 140 965 15 C38
*Condition and hardness limitations as stipulated by NACE MR0175.
TYPICAL MECHANICAL PROPERTIES FOR ANNEALED CORROSION-RESISTANT ALLOYS
AlloyYield Strength Tensile Strength Elongation Hardness
ksi MPa ksi MPa % Rockwell
MONEL alloy 400 35 214 80 552 40 B65
INCONEL alloy 600 45 310 95 655 40 B80
INCONEL alloy 625 80 552 135 931 45 B95
INCONEL alloy C-276 60 414 115 793 50 B90
INCOLOY alloy 25-6MO 48 331 100 690 42 B88
INCOLOY alloy 27-7 MO 60 415 120 830 50 B90
INCOLOY alloy 800 35 214 85 586 45 B70
INCOLOY alloy 825 45 310 100 690 45 B85
M A T E R I A L S S E L E C T I O N
25
Below. An ‘Indair’ flare at the
works of the fabricator, F.
Atkinson Ltd., Nottingham,
England. The tulip is made of
INCOLOY alloy 800HT,
mounted above a cone of
INCOLOY alloy DS.
Above. A 236 ft (72 m) flare
tower with stack and flare-
tip components of
INCOLOY alloys 800HT
and 825.
M A T E R I A L S S E L E C T I O N
WEIGHTS AND PRESSURE RATINGS OF TUBING AND CASING (cont. on p.23)
Nominal Weight, Calculated Plain -End Weight
Threads and INCOLOY alloy 825,Outside Diameter Wall Thickness Coupling INCONEL alloy G-3
INCONEL alloy C-276
in mm in mm lb/ft kg/m lb/ft kg/m lb/ft kg/m
23/8 60.3 0.190 4.83 4.60 6.85 4.60 6.85 5.02 7.47
0.254 6.45 5.80 8.63 5.97 8.88 6.52 9.70
0.336 8.53 7.70 11.46 7.59 11.30 8.29 12.34
27/8 73.0 0.217 5.51 6.40 9.52 6.38 9.49 6.97 10.37
0.276 7.01 7.80 11.61 7.95 11.83 8.68 12.92
0.308 7.82 8.60 12.80 8.76 13.04 9.56 14.23
0.340 8.64 9.50 14.14 9.54 14.20 10.42 15.51
0.440 11.18 11.65 17.34 11.87 17.66 12.96 19.29
31/2 88.9 0.254 6.45 9.20 13.69 9.13 13.59 9.97 14.84
0.289 7.34 10.20 15.18 10.27 15.28 11.22 16.70
0.375 9.52 12.70 18.90 12.98 19.32 14.17 21.09
0.476 12.09 15.80 23.51 15.95 23.74 17.41 25.91
4 101.6 0.262 6.65 11.00 16.37 10.85 16.15 11.85 17.63
0.330 8.38 13.40 19.94 13.42 19.97 14.65 21.80
0.415 10.54 15.89 23.65 16.49 24.54 18.01 26.80
0.500 12.70 19.00 28.28 19.40 28.87 21.18 31.52
41/2 114.3 0.271 6.88 12.60 18.75 12.70 18.90 13.87 20.64
0.290 7.37 13.50 20.09 13.52 20.12 14.76 21.97
0.337 8.56 15.50 23.07 13.54 23.13 16.97 25.25
0.430 10.92 19.20 28.57 19.40 28.87 21.18 31.52
0.500 12.70 21.60 32.14 22.17 32.99 24.20 36.01
0.560 14.22 24.60 36.61 24.45 36.39 26.70 39.73
5 127.0 0.253 6.43 13.00 19.35 13.31 19.81 14.53 21.62
0.296 7.52 15.00 22.32 15.43 22.96 16.85 25.08
0.362 9.19 18.00 26.79 18.61 27.69 20.32 30.24
0.422 10.72 20.80 30.95 21.41 31.86 23.38 34.79
0.478 12.14 23.20 34.53 23.96 35.66 26.16 38.93
0.500 12.70 24.10 35.86 24.94 37.11 27.23 40.52
0.560 14.22 27.00 40.18 27.55 41.00 30.08 44.76
51/2 139.7 0.275 6.98 15.50 23.07 15.92 23.69 17.38 25.86
0.304 7.72 17.00 25.30 17.50 26.04 19.11 28.44
0.361 9.17 20.00 29.76 20.56 30.60 22.45 33.41
0.415 10.54 23.00 34.23 23.39 34.81 25.53 37.99
65/8 168.3 0.288 7.32 20.00 29.76 20.23 30.11 22.09 32.87
0.352 8.94 24.00 35.72 24.47 36.42 26.72 39.76
0.417 10.59 28.00 41.67 28.70 42.71 31.33 46.62
0.475 12.06 32.00 47.62 32.39 48.20 35.36 52.62
7 177.8 0.272 6.91 20.00 29.76 20.28 30.18 22.15 32.96
0.317 8.05 23.00 34.23 23.49 34.96 25.64 38.16
0.362 9.19 26.00 38.69 26.63 39.63 29.08 43.28
0.408 10.36 29.00 43.16 29.81 44.36 32.55 48.44
0.453 11.51 32.00 47.62 32.87 48.92 35.89 53.41
0.498 12.65 35.00 52.09 35.89 53.41 39.18 58.31
0.540 13.72 38.00 56.55 38.66 57.53 42.21 62.82
*Based on 87.5% remaining body wall26
WEIGHTS AND PRESSURE RATINGS OF TUBING AND CASING (continued)
Yield Strength:110,000 psi (758 MPa) Yield Strength:125,000 psi (862 MPa) Yield Strength:130,000 psi (896 MPa)
Collapse Internal Yield Collapse Internal Yield Collapse Internal YieldOutside Diameter Pressure* Pressure* Pressure* Pressure* Pressure* Pressure*
in mm 1000 psi MPa 1000 psi MPa 1000 psi MPa 1000 psi MPa 1000 psi MPa 1000 psi MPa
23/8 60.3 16.13 111.2 15.40 106.2 17.90 123.4 17.50 120.7 18.47 127.4 18.20 125.5
21.01 144.9 20.59 142.0 23.88 164.7 23.39 161.3 24.83 171.2 24.33 167.8
26.72 184.2 27.23 187.7 30.36 209.3 30.95 213.4 31.58 217.7 32.19 222.0
27/8 73.0 14.55 100.3 14.53 100.2 16.07 110.8 16.51 113.8 16.56 114.2 17.17 118.4
19.09 131.6 18.48 127.4 21.70 149.6 21.00 144.8 22.56 155.6 21.84 150.6
21.04 145.1 20.62 142.2 23.91 164.9 23.43 161.5 24.87 171.5 24.37 168.0
22.94 158.2 22.77 157.0 26.07 179.8 25.87 178.4 27.11 186.9 26.90 185.5
28.52 196.6 29.46 203.1 32.41 223.4 33.84 233.3 33.70 232.4 34.82 240.1
31/2 88.9 13.53 93.3 13.97 96.3 14.89 102.7 15.87 109.4 15.33 105.7 16.51 113.8
16.67 114.9 15.89 109.6 18.94 130.6 18.06 124.5 19.56 134.9 18.78 129.5
21.05 145.1 20.62 142.2 23.92 164.9 23.44 161.6 24.87 171.5 24.37 168.0
25.85 178.2 26.18 180.5 29.38 202.6 29.75 205.1 30.55 210.6 30.94 213.3
4 101.6 11.06 76.3 12.61 86.9 12.03 82.9 13.33 91.9 12.33 85.0 14.40 99.3
16.65 114.8 15.88 109.5 18.92 130.5 18.05 124.5 19.53 134.7 18.77 129.4
20.46 141.1 19.97 137.7 23.24 160.2 22.69 156.4 24.17 166.7 23.60 162.7
24.06 165.9 24.06 165.9 27.34 188.5 27.34 188.5 28.44 196.1 28.44 196.1
41/2 114.3 9.21 63.5 11.59 79.9 9.89 68.2 13.17 90.8 10.09 69.6 13.70 94.5
10.68 73.6 12.41 85.6 11.60 80.0 14.10 97.2 11.88 81.9 14.66 101.1
14.34 98.9 14.42 99.4 15.84 109.2 16.38 112.9 16.31 112.5 17.04 117.5
19.01 131.1 18.39 126.8 21.61 149.0 20.90 144.1 22.47 154.9 21.74 149.9
19.80 136.5 19.25 132.7 22.50 155.1 21.88 150.9 23.40 161.3 22.75 156.9
23.97 165.3 23.96 165.2 27.24 187.8 27.22 187.7 28.31 195.2 26.83 185.0
5 127.0 5.84 40.3 9.74 67.2 6.05 41.7 11.07 76.3 6.16 42.5 11.51 79.4
8.85 61.0 11.40 78.6 9.48 65.4 12.95 89.3 9.66 66.6 13.47 92.9
13.47 92.9 13.94 96.1 14.82 102.2 15.84 109.2 15.25 105.1 16.47 113.6
17.00 117.2 16.25 112.0 19.32 133.2 18.46 127.3 20.09 138.5 19.20 132.4
19.02 131.1 18.40 126.9 21.68 149.5 20.91 144.2 22.48 155.0 21.75 150.0
19.80 136.5 19.25 132.7 22.50 155.1 21.88 150.9 23.40 161.3 22.75 156.9
21.88 150.9 21.56 148.7 24.86 171.4 24.50 168.9 25.86 178.3 25.48 175.7
51/2 139.7 5.63 38.8 9.63 66.4 5.89 40.6 10.94 75.4 5.99 41.3 11.38 78.5
7.48 51.6 10.64 73.4 7.89 54.4 12.09 83.4 8.00 55.2 12.58 86.7
11.10 76.5 12.63 87.1 12.08 83.3 14.36 99.0 12.39 85.4 14.93 102.9
14.54 100.3 14.52 100.1 16.06 110.7 16.51 113.8 16.55 114.1 17.17 118.4
65/8 168.3 4.03 27.8 8.37 57.7 4.17 28.8 9.51 65.6 4.20 29.0 9.89 68.2
6.73 46.4 10.23 70.5 7.02 48.4 11.62 80.1 7.09 48.9 12.09 83.4
10.16 70.1 12.12 83.6 10.99 75.8 13.77 94.9 11.25 77.6 14.32 98.7
13.20 91.0 13.80 95.2 14.55 100.3 15.68 108.1 14.95 103.1 16.31 112.5
7 177.8 2.98 20.5 7.48 51.6 2.98 20.5 8.50 58.6 2.98 20.5 8.84 61.0
4.44 30.6 8.72 60.1 4.65 32.1 9.91 68.3 4.69 32.3 10.30 71.0
6.23 43.0 9.95 68.6 6.45 44.5 11.31 78.0 6.49 44.7 11.76 81.1
8.53 58.8 11.22 77.4 9.11 62.8 12.75 87.9 9.27 63.9 13.26 91.4
10.78 74.3 12.46 85.9 11.71 80.7 14.16 97.6 12.00 82.7 14.72 101.5
13.03 89.8 13.69 94.4 14.31 98.7 15.56 107.3 14.72 101.4 16.18 111.6
15.11 104.2 14.85 102.4 16.76 115.6 16.87 116.3 17.26 119.0 17.55 121.0
*Based on 87.5% remaining body wall
27
SPECIFICATIONS AND DESIGNATIONSFOR NICKEL ALLOYS USED IN OIL-COUNTRY APPLICATIONS
Alloy UNS NACE ASTM ASME SAE AMS BS DIN Werkstoff Nr. VdTÜVMONEL alloy 400 N04400 MR-01-75 B 127 SB-127 4544 3072-3076 17743 2.4360 263
B 163-165 SB-163-165 4574,4575 17750-54B 366 SB-366 4675B 564 SB-564 4730, 4731B 725 SB-751 7233B 730 SB-775B 751 SB-829B 775B 829
MONEL alloy R-405 N04405 MR-01-75 B 164 SB-164 4674 – – – –7234
MONEL alloy K-500 N05500 MR-01-75 B 865 – 4676 3072-3076 17743 2.4375 –17752-54
INCONEL alloy 600 N06600 MR-01-75 B 163 SB-163 5540 3072-3076 17742 2.4816 305B 166-168 SB-166-168 5580 17750-54
B 366 SB-366 5665B 516-517 SB-516-517 5687
B 564 SB-564 7232B 751 SB-751B 775 SB-775B 829 SB-829
INCONEL alloy 625 N06625 MR-01-75 B 366 SB-366 5581 3072 17744 2.4856 499B 443-444 SB-443, 444 5599 3074 17750-52
B 446 SB-446 5666 3076B 564 SB-564 5837
B 704-705 SB-704-705 5869B 751 SB-751B 775 SB-775B 829 SB-829
INCONEL alloy 718 N07718 MR-01-75 B 637 SB-425 5589, 5590 – – 2.4668 –B 670 SB-637 5596, 5597
5662-566458325962
INCONEL alloy 725 N07725 MR-01-75 B 805 SB-443, 444 – – – – –SB-446
INCONEL alloy X-750 N07750 MR-01-75 B 637 SB-637 5542 HR505 – 2.4669 –5582, 5583
55985667-56715698, 5699
5747INCONEL alloy G-3 N06985 MR-01-75 B 366 SB-366 – – 17744 2.4619 –
B 581, 582 SB-582 17750-52B 619 SB-619B 622 SB-622B 626 SB-626B 751 SB-751B 775 SB-775B 829 SB-829
INCONEL alloy C-276 N10276 MR-01-75 B 366 SB-366 – – 17744 2.4819 400-12.98B 564 SB-582 17750-52
B 574, 575 SB-619B 619 SB-622B 622 SB-626B 626 SB-751B 751 SB-775B 775 SB-829B 829 –
INCONEL alloy 050 N06950 MR-01-75 – – – – – – –INCOLOY alloy 800 N08800 MR-01-75 B 163 SB-163 5766 3072-3076 470 1.4876 412
B 366 SB-366 5871B 407-409 SB-407-409B 514, 515 SB-514, 515
B 564 SB-564B 751 SB-751B 775 SB-775B 829 SB-829
INCOLOY alloy 825 N08825 MR-01-75 B 163 SB-163 – – – – –B 366 SB-366
B 423-425 SB-423-425B 564 SB-564
B 704, 705 SB-704, 705B 751 SB-751B 775 SB-775B 829 SB-829
INCOLOY alloy 925 N09925 MR-01-75 – SB-423-425 – – – – –SB-564
INCOLOY alloy 8926 MR-01-75 B 366 SB-366 – – – 1.4529 –25-6MO B 472 SB-625
B 625 SB-649B 649 SB-673, 674
B 673, 674 SB-677B 677 SB-751B 751 SB-775B 775 SB-804B 804 SB-829B 829
INCOLOY alloy 028 N08028 MR-01-75 B 668 SB-668 – – – 1.4563 –B 709 SB-709
M A T E R I A L S S E L E C T I O N
P A R T 3
EFFECTS OFWELL
ENVIRONMENTS
E F F E C T S O F W E L L E N V I R O N M E N T S
Corrosive well environments degrade materials in three general
ways:
1. Weight-loss corrosion, in which the metal surface is more or
less uniformly attacked.
2. Pitting or crevice corrosion, in which metal
loss is highly localized.
3. Environment-induced cracking, in which brittle fracture
occurs with no significant metal loss.
WEIGHT-LOSS CORROSION (GENERAL CORROSION)
The complexity of a material affects its resistance to weight-loss
corrosion. Carbon dioxide dissolved in the liquid phase creates
an acidic solution that can cause rapid weight-loss corrosion of
carbon steels, even at relatively low temperatures. Chlorides and
H2S increase the corrosivity of the solution. Martensitic stain-
less steels are also susceptible to weight-loss corrosion, espe-
cially at high temperatures with chlorides or H2S present.
Duplex and austenitic stainless steels have higher resistance to
weight-loss corrosion. Nickel alloys generally show complete
resistance to weight-loss corrosion even under conditions of
high temperatures and high concentrations of chlorides and
H2S.
When dissimilar metals are in contact while exposed to an aque-
ous environment, galvanic effects can cause or alter corrosion
reactions. The less noble metal in the galvanic couple is corrod-
ed at a higher rate than would occur if the metal were exposed
alone. The effect is more pronounced if the surface area of the
less noble metal is small in relation to the more noble metal. In
general, nickel alloys and austenitic stainless steels are similar
enough in corrosion potential that galvanic corrosion is not a
serious problem when couples are formed within or between the
two materials groups. However, galvanic corrosion is a possi-
bility when highly alloyed materials are connected to carbon
steels, alloy steels, or martensitic stainless steels.
LOCALIZED CORROSION
Pitting and crevice corrosion have similar consequences:
localized destruction of metal. However, the two forms of
corrosion operate by different mechanisms. Pitting occurs
when a point location becomes anodic to the surrounding
metal, resulting in continuing corrosion penetration at the
anodic point. Crevice corrosion takes place when the con-
centration of metallic ions or oxygen is different in a
crevice (or under a deposit) than in the surrounding envi-
ronment. Such localized corrosion can be particularly like-
ly on materials such as stainless steels that form protective,
passive surface films. Chloride ions in the environment can
accumulate and penetrate the passive film to allow corro-
sion at the area of film removal. Nickel alloys also form
passive films. However, chromium and molybdenum,
especially the latter, are highly effective in preventing
localized corrosion. Nickel alloys used for downhole appli-
cations generally contain sufficient molybdenum and
chromium to avoid pitting and crevice corrosion.
ENVIRONMENT-INDUCED CRACKING
The combined effects of stress and certain corrosive environ-
ments can cause failure of metals not by
mass loss but by brittle fracture at stress levels substantially
under a metal’s yield strength. Tubing strings are unavoidably
under high stress, and sour wells present a corrosive environ-
ment that can induce cracking. In deep, sour gas wells, the
avoidance of environmental cracking is often the primary con-
sideration in materials selection. The problem is compounded
by several interacting factors. As well depth increases, more
strength is required in the tubing string, and, in general, metals
are more susceptible to cracking as their strength and hardness
increase. To that situation is added that both stress and
aggressiveness of environment increase with depth.
Materials selection is critical. It must be determined with
certainty that the selected material will not undergo cracking
in the particular well environment. Failure of tubing by envi-
ronmental cracking can be sudden, with no foretelling evi-
dence such as wall thinning by corrosion.
30
Crevice corrosion under
removed bolts.
Weight-corrosion, also
called general corrosion,
results in nearly uniform dete-
rioration of a metal’s surface.
Pitting is localized pene-
tration, normally at many dif-
ferent sites. The metal between
pits is relatively unaffected
although pits may become
connected as attack progress-
es.
2
1
1
2
3
31
Stress-corrosion crack-
ing in stainless-steel vessel
and tube.
Crevices and surface
deposits can result in different
concentrations
of dissolved matter, such
as metal ions, leading to
accelerated local
corrosion.
4
6 7+
4
6
32
E F F E C T S O F W E L L E N V I R O N M E N T S
In sour wells, environmental cracking can occur by two dif-
ferent mechanisms: hydrogen embrittlement and stress cor-
rosion.
Hydrogen embrittlement involves a cathodic reaction in
which hydrogen ions are reduced to elemental hydrogen.
Hydrogen ions may result from galvanic corrosion of con-
nected dissimilar metals or from acidizing operations per-
formed on the reservoir. In sour wells, however, the major
source is usually dissolved H2S in well fluids. Elemental
hydrogen absorbed by a metal can lower ductility to the
point where the metal becomes embrittled. If the metal is
under sufficient stress, cracking results. Such cracking in
H2S environments is termed sulfide stress cracking (SSC).
Hydrogen embrittlement and SSC are essentially low-tem-
perature phenomena with maximum severity occurring in
the room-temperature range.
Stress corrosion involves an anodic reaction in which a crack
is initiated and propagated in stressed metal by dissolution of
metal ions. Metal loss continues at the leading edge of the
crack until brittle fracture occurs. Such stress-corrosion
cracking (SCC) can be caused by various media. In sour
wells, SCC can result from two corrosive species:
chloride ions and H2S. Chloride SCC normally is not
a problem with ferritic materials and nickel alloys. Austenitic
stainless steels, especially those of relatively low nickel con-
tent, can suffer chloride SCC at
7
5 Magnified (100X) appearance of stress-
corrosion cracking.
33
E F F E C T S O F W E L L E N V I R O N M E N T S
temperatures as low as 140°F (60°C) and become more sus-
ceptible at higher temperatures.
Stress-corrosion cracking induced by H2S is similar to chlo-
ride SCC but affects a broader range of materials, including
nickel alloys. This form of environmental cracking is often
the major factor in overcoming the effects of sour well envi-
ronments on materials. The potential for SCC becomes
greater with higher temperatures and concentrations of H2S
and with the presence of chloride ions
and elemental sulfur. Extremely hot and sour wells require
corrosion-resistant alloys with high contents of nickel,
chromium and molybdenum.
Virtually all metallic materials are susceptible to
SSC or SCC in sour environments, although the conditions
for susceptibility vary widely. A major factor is the concen-
tration of dissolved H2S, which increases with partial pres-
sure of the gas. Low-alloy and carbon steels are vulnerable
to SSC at partial pressure of H2S as low as about 0.05 psi
(345 Pa). By definition (NACE MR-01-75) a well with a
partial pressure of H2S greater than 0.05 psi (345 Pa) is des-
ignated as sour. If a well is sour, downhole components
must be made of a corrosion-resistant alloy that will resist
the particular sour conditions.
The classic indicator of susceptibility to chloride-ion stress-corrosion cracking is the boiling 42% magnesium chloridetest. The test has shown that alloys containing more than about45% nickel are immune to chloride stress cracking.
34
P A R T 4
CORROSION TESTING
C O R R O S I O N T E S T I N G
Nickel alloys used for downhole service do not undergo
localized corrosion or chloride-ion stress corrosion cracking
in sour well environments and experience only slight weight-
loss corrosion. Levels of C02 and chlorides – important fac-
tors in evaluating stainless and carbon steels – are generally
negligible when nickel alloys are considered. Environmental
cracking induced by H2S, either sulfide stress cracking (SSC)
or stress-corrosion cracking (SCC), is the operative mode of
potential failure for nickel alloys.
Most nickel alloys are resistant to SSC and SCC with the
degree of resistance depending on alloy composition,
strength level, stress level, temperature, and amount of H2S in
the environment. Laboratory tests using different combina-
tions of those variables can determine conditions under which
alloys do or do not suffer cracking. Two widely used tests are
the C-ring test and the slow-strain-rate test. Both tests involve
exposure of specimens to simulated sour well environments,
but at stress levels substantially higher than normal service
conditions.
The C-ring test uses a specimen made from a portion of tub-
ing cross section with circumferential stress applied by a
tightened bolt. Aformula is used to relate deflection of the C-
ring to axial tensile yield strength of the material. A stress
equal to 100% of yield strength (0.2% offset) is frequently
applied. The stressed C-ring is exposed to a sour environ-
ment and periodically inspected for cracking.
A standard environment for SSC is the NACE
Solution, which is stipulated by test standards of
the National Association of Corrosion Engineers. It consists
of 5% sodium chloride and 0.5% acetic acid in distilled water
saturated with hydrogen sulfide. The NACE test (TM-01-77)
is conducted at room temperature and atmospheric
1
2
3
36
Alloys are evaluat-
ed in a fully equipped corro-
sion laboratory that includes
autoclaves for testing at high
pressures and temperatures.
Alloys are exposed to vari-
ous corrosive environ-ments in
the laboratory to predict their
performance under service
conditions.
Special Metals maintains
extensive computerized corro-
sion data in both proprietary
and commercial systems. Test
results such as slow-strain-rate
data can be presented by com-
puter.
1 2+
4
5 6 7 8+ + +
3+
4 5
6
7
8
37
C O R R O S I O N T E S T I N G
pressure. The alloy C-rings are often galvanically coupled to
carbon steel to expose the specimen to hydrogen that evolves
as the steel corrodes. Stressed C-rings, normally not coupled
to steel, are also used in autoclave tests to determine resist-
ance to SCC at high temperatures and pressures.
The slow-strain-rate test determines resistance to SCC. A
tensile specimen is exposed to the sour environment while
being subjected to stress that produces a constant, slow rate
of strain. The results are normally compared with a slow-
strain rate test performed in air at the same strain rate.
Differences between the two tests in time to fracture, percent
elongation, and percent reduction of area indicate the effect
of the sour environment on the material. Ratios of test-solu-
tion values to air values are often used as gauges of a mate-
rial’s performance. Because the slow-strain-rate test causes
continual rupturing of any passive films on the specimen, it
may be more severe than the C-ring test.
Another test sometimes used to evaluate materials in sour
environments is the constant-load test. The specimen is
exposed to the environment while under an unvarying ten-
sile load.
The accompanying tables and charts indicate the resistance
of Special Metals products to various environments in dif-
ferent test types. In the slow-strain-rate tests, the strain rate
was 4x10-6 s-1 unless otherwise noted. Test solutions were
made up with distilled water along with amounts of corro-
sive species as described with the test results.
As shown by the results of tests in environments containing
elemental sulfur, wells in sour formations that also contain
free sulfur are especially harsh environments. The presence
of free sulfur can deduct 50°F (30°C) or more from the tem-
perature capability of an otherwise resistant alloy.
9
C-ring specimen used to determing resistance to sul-
fide stress cracking and stress-corrosion cracking,
38
Slow-strain-rate specimen
used to detemine resistance to
sulfide stress cracking and
stress-corrosion cracking.
Apparatus for sulfide
stress-cracking testing (NACE
test).
Apparatus for slow-strain-
rate testing.
12
11
10
10
11
12
39
C-RING TESTS IN NACE SOLUTIONa
Yield Strength(0.2% Offset) Sulfide
Material Simulated Hardness, Duration, StressAlloy Condition Well Age 1000 psi MPa RC Days Cracking
INCONEL alloy 625 Cold Worked None 125.0 862 30.5 42 NoCold Worked None 160.0 1103 37.5 10 YesCold Worked None 176.0 1214 41 6 Yes
INCONEL alloy 718 Age Hardened None 120.0 827 30 42 NoAge Hardened None 130.0 896 37 42 NoAge Hardened None 134.0 924 38.5 42 NoAge Hardened None 139.0 958 38 42 NoAge Hardened None 156.0 1076 41 60 No
INCONEL alloy 725 Cold Worked None 90.0 621 25 30 NoAge Hardened None 117.6 811 37 30 NoAge Hardened None 128.6 887 40 30 NoAge Hardened 600ºF (315ºC)/1000h 130.8 902 41.5 30 NoAge Hardened None 132.9 916 36 42 NoAge Hardened None 133.0 917 39 30 NoCold Worked & Aged None 137.8 950 39 42 No
INCONEL alloy G-3 Cold Worked 600ºF (315ºC)/1000h 119.4 823 26 43 NoCold Worked 600ºF (315ºC)/1000h 132.3 912 30 43 NoCold Worked 600ºF (315ºC)/1000h 135.3 933 31 43 NoCold Worked 600ºF (315ºC)/1000h 136.9 944 - 30 No, Nob
Cold Worked 600ºF (315ºC)/1000h 137.7 949 - 30 No, Nob
Cold Worked 600ºF (315ºC)/1000h 181.7 1253 - 30 No, Yesb
INCONEL alloy C-276 Cold Worked 600ºF (315ºC)/1000h 126.6 873 32 43 NoCold Worked 600ºF (315ºC)/1000h 155.1 1069 38 43 NoCold Worked 600ºF (315ºC)/1000h 166.8 1150 35 43 NoCold Worked 600ºF (315ºC)/1000h 188.7 1301 43 43 No
INCOLOY alloy 825 Cold Worked None 138.0 952 30 42 NoCold Worked None 147.0 1014 33 42 No
INCOLOY alloy 925 Age Hardened None 114.0 786 38 42 NoCold Worked None 139.0 958 35.5 42 NoCold Worked & Aged None 176.0 1214 43.5 42 NoCold Worked & Aged None 186.0 1282 46 42 NoAge Hardened 500ºF (260ºC)/500h 113.5 783 38 42 NoCold Worked 500ºF (260ºC)/500h 139.5 962 35.5 42 NoCold Worked & Aged 500ºF (260ºC)/500h 176.0 1214 43.5 42 NoCold Worked & Aged 500ºF (260ºC)/500h 180.0 1214 44 42 NoCold Worked & Aged 500ºF (260ºC)/500h 185.5 1279 46 42 No
a Room-temperature tests at 100% of yield strength in 5% NaCl plus 0.5% acetic acid saturated with H2S. All specimens were coupled tocarbon steel.
b Duplicate test specimens.
40
C O R R O S I O N T E S T I N G
WEIGHT-LOSS TESTSa
IN H2S ENVIRONMENTS
H2SCorrosion Rate
Alloy Pressure 300°F(149°C) 400°F(204°C)
psi kPa mpy mm/y mpy mm/y
INCONEL alloy 625 10 69 0.0 0.000 0.1 0.00350 345 0.3 0.008 0.4 0.010100 690 0.1 0.003 0.2 0.005
INCOLOY alloy 825 10 69 0.1 0.003 0.1 0.00350 345 0.4 0.010 0.5 0.013100 690 0.1 0.003 0.5 0.013
INCOLOY alloy 925 10 69 0.1 0.003 0.1 0.00350 345 0.4 0.010 0.5 0.013100 690 0.1 0.003 0.4 0.010
INCONEL alloy 718 10 69 3.0 0.076 0.3 0.00850 345 0.7 0.018 2.3 0.058100 690 0.1 0.003 1.2 0.030
MONEL alloy K-500 10 69 27 0.69 1.1 0.2850 345 78 1.98 113 2.87100 690 221 5.61 169 4.29
9Cr/1Mo Steel 50 345 206 5.23 278 7.06100 690 299 7.59 172 4.37
a Autoclave tests of 14-day duration in 15% NaCl/distilled water with total gas pressure of 1000 psi (6.9 MPa) consisting of 500 psi (3.4 MPa) C02 plus N2 and H2S.
WEIGHT-LOSS TESTSa
IN FREE-SULFUR ENVIRONMENTS
Corrosion Rate
Alloy Test Mediab mpy mm/y
INCONEL alloy C-276 A 0.2 0.005B 0.1 0.003
INCONEL alloy 625 A 0.7 0.018B 0.2 0.005
INCOLOY alloy 925 A 1.1 0.028B 1.2 0.030
INCOLOY alloy 825 A 1.1 0.028B 1.6 0.041
AISI Type 316 A 3.9 0.099B 4.5 0.114
a Autoclave tests of 15-day duration on unstressed coupons.b Solution A: 15% NaCl plus 200 psi (1380 kPa) H2S Plus
100psi (690 kPa) C02 plus 1 g/L of sulfur at 450°F (232°C).Solution B: 25% NaCl plus 200psi (1380 kPa) H2S Plus100psi (690 kPa) C02 Plus 1 g/L of sulfur at 400°F (204°C).
STRESS-CORROSION-CRACKING TESTSa IN FREE-SULFUR ENVIRONMENT
Yield Strength Stress-Corrosion Cracking(0.2% Offset)
Material 350°F 375°F 400°F 425°F 450°F 475°F 5OO°FAlloy Condition 1000 psi Mpa (177°C) (191°C) (204°C) (218°C) (232°C) (246°C) (26O°C)
INCONEL alloy 718 Age Hardened 130.3 898 Yesc -
INCONEL alloy 625 Cold Worked 144.0 993 No Yes -Cold Worked 160.0 1103 No Yes -
INCONEL alloy C-276 Cold Worked 127.0 876 No No No No No No NoCold Worked 155.0 1069 No No No No No No YesCold Worked 167.0 1151 No No No No No No NoCold Worked 168.0 1158 No No No No No No Yes
a C-ring autoclave tests of 14-day duration at 100% of yield strength in 25% NaCl plus 0.5% acetic acid plus 1 g/L sulfur plus 120 psi (827kPa) H2S.b One of two specimens cracked.c At 275°F (135°C),
41
C O R R O S I O N T E S T I N G
42
STRESS-CORROSION-CRACKING TESTSa
IN HIGH-TEMPERATURE SOUR ENVIRONMENTS
Yield Strength(0.2% Offset) Stress
Material Hardness, Test Duration, CorrosionAlloy Condition 1000 psi MPa RC Mediab Days Cracking
INCONEL alloy 625 Cold Worked 128.0 883 37 A 15 NoCold Worked 177.1 1221 41 A 15 NoCold Worked 128.0 883 37 B 15 NoCold Worked 177.1 1221 41 B 15 NoCold Worked 125.0 862 30.5 C 42 NoCold Worked 160.0 1103 37.5 C 42 NoCold Worked 176.0 1214 41 C 42 No
INCONEL alloy 718 Age Hardened 120.0 827 30 C 42 NoAge Hardened 134.0 924 38.5 C 42 NoCold Worked 197.0 1358 37.5 C 20 Yes
INCONEL alloy G-3 Cold Worked 133.5 920 33 D 60 NoCold Worked 133.5 920 33 D 120 NoCold Worked 137.5 948 30 D 90 YesCold Worked 137.5 948 30 D 120 NoCold Worked 183.3 1264 38 D 120 NoCold Worked 133.5 920 33 E 60 NoCold Worked 133.5 920 33 E 120 NoCold Worked 137.5 948 30 E 120 NoCold Worked 183.3 1264 38 E 120 No
INCONEL alloy C-276 Cold Worked 194.7 1342 43.5 A 15 NoCold Worked 194.7 1342 43.5 B 5 No
INCOLOY alloy 825 Cold Worked 131.0 903 30 A 15 YesCold Worked 138.0 952 30 C 42 NoCold Worked 147.0 1014 33 C 42 No
INCOLOY alloy 925 Cold Worked & Aged 166.0 1145 40.5 A 15 YesAge Hardened 133.5 783 38 B 15 YesCold Worked & Aged 185.5 1279 46 B 15 YesAge Hardened 114.0 786 38 C 42 NoCold Worked 139.0 958 35.5 C 42 NoCold Worked & Aged 176.0 1214 43.5 C 42 NoCold Worked & Aged 185.5 1279 46 C 42 No
a Autoclave tests on C-ring specimens stressed at 100% of yield strength.b Test Media:
A = 15% NaCl plus 200 psi (1380 kPa) H2S PIUS 100 PSi (690 kPa) C02 plus 1 g/L of suifur at 450ºF (232ºC).B = 25% NaCl plus 200 psi (1380 kPa) H2S PIUS 100 PSi (690 kPa) C02 plus 1 g/L of sulfur at 400ºF (204ºC).C = 15% NaCl saturated with H2S plus 1000 psi (6.9 MPa) gas phase of 1% H2S, 50% C02, 49% N2 at SOOºF(260ºC).D = 25% NaCl plus 100 psi (690 kPa) H2S plus 200 psi (1380 kPa) C02 at 400ºF (204ºC).E = Same as D but at 425ºF (218ºC).
43
wwwwww..ssppeecciiaallmmeettaallss..ccoomm
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