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This family of diamond products has been
initially developed with one main objective,
i.e. substitute naturally-mined diamonds,
for which supply is irregular or even scarce,
for synthetic diamonds.
Big natural stones, or drillings, originating
from unstable areas, are subject to catastrophic
failure due to cleavage, whereas Carbonado,
the natural polycrystalline form of diamond,
extremely tough and best suited for hard
drilling, are very rare. That is how synthetic
diamonds have become an interesting option.
Being limited in size (for economic reasons),
agglomerates have been designed.
These are called TSP, which stands for Thermally
Stable Polycrystalline diamond products.
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This material is almost
as strong and hard as single crystal
diamond and present one considerable
advantage: in spite of its strength,
single crystal diamond fractures
relatively easily along cleavage
planes. In polycrystalline diamond,
crystals are randomly oriented, limiting
cracks to the boundaries of each
crystal.
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This is one of the reasons explaining the
high toughness of polycrystalline diamonds.
Their exceptional strength also largely
depends on the strength and extent of the
diamond to diamond bonds.
TSP products consist
of micron sized diamond crystals,
combined to a bonding system usually
made of silicon or a blend of silicon
and other metal components, such
as iron, aluminium, titanium,
As their name also clearly indicates it,
TSP show a very high thermostability. They
can withstand high temperatures of about
1200C (to a great extent because of the
presence of silicon as bonding agent).
Thanks to this exceptional property, TSP
products are best suited for manufacturing
tools by means of high temperature - high
pressure infiltration process.
From field observations,
it has been established that, thanks
to their specific characteristics,
TSP diamond cutters are reducing
overall system costs by increasing
rates of penetration and bit life
in abrasive and hard rock applications.
TSP Qualification method
Custodiam has developed, within its laboratory,
a new method aimed at evaluating the quality
of TSP products.
This quantitative method is based on the
wear level observed after testing process.
The procedure could be described as follows:
Several TSP pieces are placed in a jar set
in a kind of "spin dryer" at a speed maintained
constant and controlled during the whole
process by means of a tachometer.
During the process, TSP will move according
to a specific scheme and be subject to wear
by friction. In order to prevent any impact
factor, several absorbing elements can be
added to the testing procedure (for instance
water).
After testing, pieces will present a weakening,
more or less important (such as rounded edges),
characterized by a weight loss (US value).
The same experiment will be applied on TSP
pieces, which have previously been submitted
to a heat treatment (USTh value). This treatment
consists of heating the pieces at high temperature
in a pipe hermetically closed, containing
a fixed initial concentration of oxygen.
By combining wear results (before and after
heat treatment), we are able to qualify the
TSP product and attribute a performance index.
This testing procedure
allows us to distinguish premium
quality TSP from Standard quality
(offering a good price/quality ratio),
but to also identify low quality
products. This difference has been
clearly illustrated on the pictures
here below.
WEAR EFFECTS CORRESPONDING TO PERFORMANCE INDEX
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BEFORE TREATMENT |
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PERFECT SHAPE SHARP EDGES AND TIPS
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P.I. 75 |
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P.I. 65 |
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SLIGHT CHANGES IN SHAPE AND EDGES
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P.I. 50 |
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NOTICEABLY ROUNDED
BLUNT EDGES
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P.I. 30 |
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| By means of SEM photos,
we also observe the TSP structure,
or rather the distribution and size
of diamond grits within the TSP.
By burning the diamond contained, we are
also able to isolate the structure of the
bond, clearly showing the holes left by the
burnt diamond grits, and so the grits distribution.
A more regular structure and distribution
is already a first indication of TSP quality
and probably higher performance.
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