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Materials Selection in the Oilsands Industry Based on Materials Degradation Mechanisms
Table 1: Summary of Some of the Equipment Used in the Oilsands Industry, Working Conditions and Materials
10,19
Equipment Applications Conditions Materials Surface Engineering
Blade cutting edges Roadways and material collection Abrasive wear High-grade steel PTAW WC/Ni overlays
Crusher tooth Break up mined material High-stress abrasion, indentation, gouging CrC overlays, cast iron PTAW WC/Ni overlays
Hydrotransport screens Separate and remove big rocks Corrosion, erosion–corrosion CrC overlays PTAW WC/WC/Ni overlays
Tailings pipelines Transportation of tailings Corrosion, erosion–corrosion Hardened carbon steel, CWIs Martensitic stainless steel
Centrifugal pumps Pumping of slurry and tailings Low-stress abrasion, erosion–corrosion CWIs, CrC WC-based sprayed coatings
Elbows, joints, valves Transportation of slurry and tailings Corrosion, erosion–corrosion Hardened carbon steel, CWIs Martensitic stainless steel,
application of WC/Ni, WC/
stainless steel PTAW overlays
CrC = chromium carbide; CWIs = chromium white irons; Ni = nickel; PTAW = plasma transfer arc welding; WC = tungsten carbide.
stainless steels cannot provide enough protection due to their low shovels.
10
HCS blade cutting edges are commonly used for
hardness.
13
The sand particles can also impact the impellers and casing construction or maintenance of mine-site roads; however, CWIs and
at different angles, causing erosion; if the carrier solution is corrosive CrC overlays are used to protect them when severe abrasion is
to the material, the corrosion products are easily removed by the slurry present.
4
Crusher teeth are subjected to impact and erosive wear, so
and the corrosive fluid has access to the undamaged surface.
6,13
Figure CrC overlays are applied to protect them from wear; nevertheless,
2 shows the different degradation regimes experienced in the mining the carbides can be fractured and crumbled by the effect of the
and transportation process. In the hydrotransport process it is impact energy.
18
Field and laboratory tests have demonstrated that
important to characterise the slurry flow regimes to select the best plasma transfer arc welding (PTAW)-based MMCs dramatically
material to withstand the degradation processes. improve the performance of the crushing tools and increase their
service life by up to 500%.
9,19
A homogeneous suspension is generated near the pump outlet, and
severe erosion–corrosion degrades the inner wall of pipelines, valves Basically, all of the equipment and materials used in the hydrotransport
and other devices placed near this area.
14
Sliding beds are generated process must withstand corrosion and erosion–corrosion.
3
For instance,
far from the pump outlet where the oxygen and Cl- concentrations the separation screens come into contact with the corrosive liquid in the
are reduced dramatically, changing not only the erosive but also the slurry and are subjected to an erosion–corrosion process; even though the
corrosive conditions.
3
The development of sliding beds during piping conventional CrC submerged arc wear plate offers good abrasion
can lead to the formation of oxygen concentration cells; if there is a resistance, it cannot perform satisfactorily under high-angle erosion due to
difference in the oxygen content between two areas of the pipelines, its brittle nature.
3
In previous studies, a WC–NiCrBSi PTAW overlay was
the corrosion attack will take place preferentially in the area exposed tested under severe erosion–corrosion conditions, similar to those
to the lowest oxygen concentration (the red rectangles in Figure 2).
15
observed in the separation screens; the PTAW overlay was then applied to
the surfaces of separation screens, and their service life was increased by
It has been established that in highly concentrated slurries with up to 500% compared with screens with CrC overlays.
9,19
The ductile
temperatures in the range of 20–25°C, erosion is the dominant wear Ni-based matrix conferred toughness and relatively good corrosion
process for WC-MMCs,
3,7,8
ASS and MSS
3,16
and CWIs.
3
The main resistance, the metallurgical bonding with the base metal improved
material loss mechanisms were ploughing and cutting of the matrix impact resistance and the WC hard phase reinforced the composite.
9,19
of the WC-MMCs and fracture of unsupported WC grains; WC-
MMCs performed up to 16 times better in terms of mass loss CWIs can be used in centrifugal pumps, where their carbide content
compared with the ASS, which showed severe plastic deformation.
9
confers them excellent abrasion resistance, and their corrosion
Under mild erosion–corrosion conditions, WC-MMCs showed similar performance can be dramatically improved by the correct selection of the
mass loss to the CWIs.
3
However, when the temperature of the slurry Cr/C ratio, the Cr content in the carbides and the addition of Ni to the
increased, corrosion seemed to dramatically affect the performance matrix.
20,21
WC–CoCrW and WC–NiC cermets have been demonstrated
of the WC-MMCs: selective dissolution of the matrix phase, to withstand aggressive erosion–corrosion conditions similar to those
especially around the carbides and WC grains, deteriorated the experienced by slurry pumps, and can be deposited by detonation gun or
support of the hard phases, which can be either detached by pull- high-velocity oxygen fuel (HVOF) thermal spray guns.
22,23
If corrosion
out mechanisms or fractured.
7,8
New corrosion-resistant materials performance is the primary characteristic under consideration, the HVOF
are currently being tested for use as matrix phases in WC-MMCs that coating performs best, even compared with CWIs and stainless steels.
22
have potential uses in the oilsands industry.
7,17
However, in order to maintain the corrosion resistance, the coating must
have low porosity and the carbide–binder adhesion must be
Materials in the Oilsands Industry improved.
22,24
HCS pipelines are widely used to build tailings pipelines;
Table 1 summarises the materials currently used in a number of however, CrC and MSS showed superior wear resistance.
5,10
Although
applications during the oilsands process. The surface engineering HCS may have better abrasion behaviour than MSS, it has poor corrosion
column presents some alternative coatings that are being applied resistance and its overall performance is negatively affected.
15
successfully either on-field or in the laboratory with remarkable
improvements in terms of service life. Earth-moving equipment and The identification of critical zones along the pipelines helps to
shovels are usually protected by applying CrC overlays, which show establish a materials selection methodology based on classification
moderate toughness and hardness in the range of 56–58HRC;
10
HCS of the degradation mechanisms and application of wear-resistant
and wear plates are used in the inner walls of the hauler trucks and materials. For example, in sliding beds the normal stress exerted by
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EXPLORATION & PRODUCTION – VOLUME 7 ISSUE 1
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