American Oil and Gas Reporter - September 2016 - 80

SpecialReport: Tubulars Technology

New Metallurgy Improves Performance
By William D. Nielsen
and Diane M. Nielsen
MAYFIELD HEIGHTS, OH.-Equipment is only as good as the material from
which it is made. This holds true in all
industries, but any petroleum or drilling
engineer can attest that it is especially so
in the oil and gas sector, where equipment
often is deployed in extreme and varied
operating environments, and is pushed
to the limits of endurance.
Base materials matter, whether dealing
with the high torque and friction conditions
of extended-reach horizontal drilling, the
pressure and temperature extremes of
deepwater projects, or the degrading
effects of corrosion in production operations. Conventional alloys remain the
backbone of the oil and gas industry, but
materials engineers and equipment designers recognize significant shortcomings

in the traditional materials used to construct
drilling, completion and production tools,
as well as permanent downhole and even
surface equipment, in certain applications.
In direct response to the need for materials capable of withstanding the everincreasing demands inherent in engineering
and installing a wellbore, legacy coppernickel-tin alloy (UNS C72900) has been
re-engineered with next-generation metallurgical capabilities to meet the demands
of even the most challenging field applications. The enhanced C72900 materials
enable engineers and designers to build
tools that have added capability and improved reliability, and provide more costsaving opportunities than previously were
possible without having to resort to exotic
and expensive specialty alloy products.
The properties of the high-strength,
spinodally-hardened copper-nickel-tin al-

TABLE 1
Mechanical Properties of New C72900 Tempers versus Legacy C72900
Yield strength
(ksi)

Elongation
(%)

Typical average Charpy
V-notch energy
(foot-pounds)

Improved C72900 (version 1)

Improved C72900 (version 2)

110

110-150

3-10

Legacy C72900

The new copper-nickel-tin alloy tempers achieve good longitudinal and transverse properties at larger diameters, and they can be manufactured as hollow bars directly off the
mill, offering significant cost savings by eliminating the need to machine the core from
a solid bar.

80 THE AMERICAN OIL & GAS REPORTER

loys provide many advantages in demanding end-use applications. These
alloys are lead- and beryllium-free, and
demonstrate excellent corrosion and corrosion-related stress cracking resistance
in seawater, chlorides and sulfides.
Enhanced Properties
C72900 alloys always have been preferred because of their excellent nongalling
behavior. However, use of traditional
C72900 tempers has been limited in the
past by the one mechanical characteristic-fracture toughness-that made them
inadequate for components subject to
shock loading. To address this, the existing
copper-nickel-tin alloy was re-engineered
to produce a unique material that delivers
a dramatic increase in fracture toughness
without sacrificing its high strength.
Table 1 shows the key mechanical
properties of yield strength, elongation,
and Charpy V-notch for two versions of
the new tempers compared with legacy
C72900. The Charpy V-notch impact test
determines the amount of energy absorbed
by a material, and is the standard measure
of "toughness" (i.e., ductility/brittleness).
There are many benefits to using the
improved copper alloy system in the
drilling environment. First, the material
is not magnetic, which is a particularly
important feature since magnetic interference in a horizontal or directional
drilling operation impacts the precision
with which a wellbore can be located. In
fact, there are no steels available that
display the level of nonmagnetism these
materials exhibit.
In addition, corrosion resistance as a
copper alloy system is outstanding in
drilling applications. The steels that may
be commonly used for some of the applications envisioned for copper alloys
are highly susceptible to chloride stress
corrosion, cracking and pitting, which in
many cases cause the components to be
taken out of service to avoid failure. The
new C72900 tempers resist that type of
damage.
In developing the new tempers, fracture
toughness was increased so much that
the erosion resistance became much better
than that of legacy C72900 versions. The
high speed and fast flow rates of drilling
mud and rock cuttings can erode metals.
Increased fracture toughness, therefore,
is an enhancement that increases the

American Oil and Gas Reporter - September 2016

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