Corrosion Resistant Alloys

Page 11

9

Page 35

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.

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


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


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


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.


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


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.


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


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.



*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


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.


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


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


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


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


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


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


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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