Thermal stability of ultrahard polycrystalline diamond composite materials
Thermal stability of the ultrahard polycrystalline diamond (UHPCD) composite material developed by the reinforcement of the polycrystalline diamond (PCD) with chemical vapor deposition (CVD) diamond has been investigated in a flow of argon at 1200 °C. The indentation, Raman spectra and wear test hav...
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irk-123456789-1261562017-11-17T03:02:37Z Thermal stability of ultrahard polycrystalline diamond composite materials Meng, D. Yue, W. Lin, F. Wang, C. Wu, Z. Получение, структура, свойства Thermal stability of the ultrahard polycrystalline diamond (UHPCD) composite material developed by the reinforcement of the polycrystalline diamond (PCD) with chemical vapor deposition (CVD) diamond has been investigated in a flow of argon at 1200 °C. The indentation, Raman spectra and wear test have been performed to compare hardness, C–C structure and wear resistance of untreated and thermal treated UHPCD. It has been shown that the hardness of CVD diamond in UHPCD attains 133±7 GPa after high pressure and high temperature, while after thermal treatment the hardness decreases to 109±3 GPa, and the wear resistance of the thermal treated UHPCD decreases from 0.17 to 0.6 mg/km. The narrowing of full width at half maximum and shift of Raman peak to lower frequencies of CVD diamond in thermal treated UHPCD imply a decrease of crystal structural defects and compressive stresses, which results in a drop of the hardness of CVD diamond in a thermal treated UHPCD. The higher wear rate of thermal treated UHPCD is due to the lower hardness. Досліджено термічну стабільність надтвердого полікристалічного алмазного (UHPCD) композиційного матеріалу, отриманого армуванням полікристалічного алмазу після хімічного осадження (CVD) алмазу в потоці аргону при 1200 °C. Для порівняння твердості, C–C-структури і зносостійкості необробленого та термообробленого UHPCD було досліджено заглиблення індентора, спектри комбінаційного розсіювання та знос. Показано, що твердість CVD-алмазу в UHPCD досягає 133±7 ГПа після дії високого тиску і високої температури, а після термообробки зменшується до 109±3 ГПа, зносостійкість UHPCD після термообробки зменшується від 0,17 до 0,6 мг/км. Звуження напівширини і зсув піку комбінаційного розсіювання в область низьких частот CVD-алмазу в термообробленому UHPCD характеризує зменшення кристалічних структурних дефектів і напружень стиску, що призводить до зниження твердості CVD-алмазу в термообробленому UHPCD. Вища швидкість зносу термообробленого UHPCD пов’язана з більш низькою твердістю. Исследована термическая стабильность сверхтвердого поликристаллического алмазного (UHPCD) композиционного материала, полученного армированием поликристаллического алмаза после химического осаждения (CVD) алмаза в потоке аргона при 1200 °C. Для сравнения твердости, C–C-структуры и износостойкости необработанного и термообработанного UHPCD были исследованы глубина проникновения индентора, спектры комбинационного рассеяния и износ. Показано, что твердость CVD-алмаза в UHPCD достигает 133±7 ГПа после действия высокого давления и высокой температуры, а после термической обработки уменьшается до 109±3 ГПа, износостойкость после термической обработки UHPCD уменьшается от 0,17 до 0,6 мг/км. Сужение полуширины и сдвиг пика комбинационного рассеяния в область низких частот CVD- алмаза в термообработанном UHPCD характеризует уменьшение кристаллических структурных дефектов и напряжений сжатия, что приводит к снижению твердости CVD-алмаза в термообработанном UHPCD. Более высокая скорость износа термически обработанного UHPCD связана с более низкой твердостью. 2015 Article Thermal stability of ultrahard polycrystalline diamond composite materials / D. Meng, W. Yue, F. Lin, C. Wang, Z. Wu // Сверхтвердые материалы. — 2015. — № 2. — С. 3-10. — Бібліогр.: 15 назв. — англ. 0203-3119 http://dspace.nbuv.gov.ua/handle/123456789/126156 621.921.34-419:539.533 en Сверхтвердые материалы Інститут надтвердих матеріалів ім. В.М. Бакуля НАН України |
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Получение, структура, свойства Получение, структура, свойства |
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Получение, структура, свойства Получение, структура, свойства Meng, D. Yue, W. Lin, F. Wang, C. Wu, Z. Thermal stability of ultrahard polycrystalline diamond composite materials Сверхтвердые материалы |
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Thermal stability of the ultrahard polycrystalline diamond (UHPCD) composite material developed by the reinforcement of the polycrystalline diamond (PCD) with chemical vapor deposition (CVD) diamond has been investigated in a flow of argon at 1200 °C. The indentation, Raman spectra and wear test have been performed to compare hardness, C–C structure and wear resistance of untreated and thermal treated UHPCD. It has been shown that the hardness of CVD diamond in UHPCD attains 133±7 GPa after high pressure and high temperature, while after thermal treatment the hardness decreases to 109±3 GPa, and the wear resistance of the thermal treated UHPCD decreases from 0.17 to 0.6 mg/km. The narrowing of full width at half maximum and shift of Raman peak to lower frequencies of CVD diamond in thermal treated UHPCD imply a decrease of crystal structural defects and compressive stresses, which results in a drop of the hardness of CVD diamond in a thermal treated UHPCD. The higher wear rate of thermal treated UHPCD is due to the lower hardness. |
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Meng, D. Yue, W. Lin, F. Wang, C. Wu, Z. |
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Meng, D. Yue, W. Lin, F. Wang, C. Wu, Z. |
| author_sort |
Meng, D. |
| title |
Thermal stability of ultrahard polycrystalline diamond composite materials |
| title_short |
Thermal stability of ultrahard polycrystalline diamond composite materials |
| title_full |
Thermal stability of ultrahard polycrystalline diamond composite materials |
| title_fullStr |
Thermal stability of ultrahard polycrystalline diamond composite materials |
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Thermal stability of ultrahard polycrystalline diamond composite materials |
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thermal stability of ultrahard polycrystalline diamond composite materials |
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Інститут надтвердих матеріалів ім. В.М. Бакуля НАН України |
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2015 |
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Получение, структура, свойства |
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| citation_txt |
Thermal stability of ultrahard polycrystalline diamond composite materials / D. Meng, W. Yue, F. Lin, C. Wang, Z. Wu // Сверхтвердые материалы. — 2015. — № 2. — С. 3-10. — Бібліогр.: 15 назв. — англ. |
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ISSN 0203-3119. Сверхтвердые материалы, 2015, № 2 3
Получение, структура, свойства
UDC 621.921.34-419:539.533
D. Meng, W. Yue*, F. Lin, C. Wang, Z. Wu (Beijing, China)
*cugbyw@163.com, yw@cugb.edu.cn
Thermal stability of ultrahard polycrystalline
diamond composite materials
Thermal stability of the ultrahard polycrystalline diamond (UHPCD)
composite material developed by the reinforcement of the polycrystalline diamond
(PCD) with chemical vapor deposition (CVD) diamond has been investigated in a flow
of argon at 1200 °C. The indentation, Raman spectra and wear test have been per-
formed to compare hardness, C–C structure and wear resistance of untreated and
thermal treated UHPCD. It has been shown that the hardness of CVD diamond in
UHPCD attains 133±7 GPa after high pressure and high temperature, while after
thermal treatment the hardness decreases to 109±3 GPa, and the wear resistance of the
thermal treated UHPCD decreases from 0.17 to 0.6 mg/km. The narrowing of full
width at half maximum and shift of Raman peak to lower frequencies of CVD diamond
in thermal treated UHPCD imply a decrease of crystal structural defects and
compressive stresses, which results in a drop of the hardness of CVD diamond in a
thermal treated UHPCD. The higher wear rate of thermal treated UHPCD is due to the
lower hardness.
Keywords: ultrahard polycrystalline diamond, thermal stability, CVD
diamond, wear resistance.
INTRODUCTION
Generally, polycrystalline diamond (PCD) materials are used as
cutting inserts in drilling bits. The performance and service life of drilling bits are
usually determined by mechanical properties of PCD. It is well known that PCD
with extensive diamond–diamond bonding can be synthesized under high pressure
and high temperature (HPHT) by using metallic powders as sintering agents.
However, a large amount of metallic agents in the PCD could cause deterioration
such as graphitization or cracking above about 700 °C [1, 2]. Therefore, the
working temperature of sintered diamond has been limited to 700 °C.
To synthesize PCD with a high thermal stability, an alternative approach is to
use unconventional non-metallic sintering agents such as calcium carbonate and
magnesium carbonate. Akaishi et al. [3] investigated the behavior of magnesium
carbonate (MgCO3) as sintered agent at 7.7 GPa and 1800–2450 °C in a belt press
[3]. PCD sintered with MgCO3 showed no drop of Vickers hardness until after a
© D. MENG, W. YUE, F. LIN, C. WANG, Z. WU, 2015
www.ism.kiev.ua/stm 4
heat treatment above 1300°C for 30 min in a vacuum of 1⋅10−3–1.5⋅10−3 Pa.
Westraadt et al. reported the synthesis and characterization of PCD sintered with
CaCO3 at 8±0.5 GPa and 2000–2200 °C in a 6–8 Kawai type multianvil high
pressure apparatus [4]. No wear resistance reduction of PCD was detected after a
heat treatment to 1200°C in vacuum (5⋅10−3 Pa) for 30 min in a machining test on a
silica resin bar. However, because of the limitation of extremely high pressure and
high temperature conditions, only a few of carbonate sintered PCD toward has
been applied in industrial field.
Shulzhenko et al. [5] reported a new approach to sintering superhard material
named the ultrahard polycrystalline diamond (UHPCD) composite material. The
basis for manufacturing the UHPCD was a combination of the high-pressure
technique and chemical vapor deposition (CVD) method. Superior hardness and
excellent wear resistance are the main features of UHPCD. The hardness of the
CVD diamond in UHPCD is as high as 140 GPa, which is higher than that of
natural diamond single crystal. The hardness of PCD in the UHPCD is about 50
GPa. The wear resistance of the hybrid UHPCD in turning granite of the XI drilla-
bility index is higher than that of PCD by a factor of 14. Shulzhenko et al. [6]
investigated also a thermal stability of the PCD material. It was found that the PCD
retained hardness 23 GPa at a temperature of 1200 K, while the initial hardness
was 44.8 GPa. However, the thermal stability of the UHPCD has not been studied.
In this study, the thermal stability of the UHPCD was investigated at 1200 °C in
flow of argon. It contrasted the hardness, wear performance and Raman spectrum
of the UHPCD before and after thermal treatment. The mechanism of the decreased
mechanical properties of the CVD diamond in thermal treated UHPCD was further
discussed.
EXPERIMENTAL
Materials
A diamond micron powder and CVD diamond were used as the raw materials.
The diamond powder had grains of sizes from 20 to 30 μm. The CVD diamond
with a size of 0.8×0.8×4 mm was produced by a deposition in the microwave
frequency plasma in methane–hydrogen mixtures. The UHPCD samples were
sintered by the same method as in the previous report [5]. The UHPCD samples
(4 mm in diameter and 4.5 mm high) were chemically purified to remove graphite
residues. The optical image of UHPCD is shown in figure. The characteristic
feature of the UHPCD is a reinforced CVD diamond surrounded by PCD.
500 μm
PCD CVD diamond
Optical image of UHPCD.
ISSN 0203-3119. Сверхтвердые материалы, 2015, № 2 5
Characterization
The UHPCD sample was heated to 1200 °C in argon for 10 min. After that, the
sample was cooled to room temperature under argon flow. The weight loss was
calculated from the weight of the sample before and after the thermal treatment.
The hardness of the CVD diamond was determined using a PTM-3
microhardness tester with a Vickers diamond pyramid as an indenter. The hardness
value was found by the generally accepted formula HV = 1.8544P/d2, where P is
the indentation load, d is the arithmetical mean of two diagonals of the indent. The
measurements were performed under loads of 4.9 and 9.8 N. The indent diagonals
were measured using a Neophot optical microscope.
The chosen indentation loads may be considered optimal, as in using both of
them the obtained hardness values were practically the same, and in addition,
during the indentation no fracture of the tested material was observed. During the
hardness measurements, a particular attention was paid to the state of the diamond
pyramid tip, which was assessed by measuring indents on the polished surfaces of
standard specimens with the hardness of about 4 GPa. After each three
measurements of the tested samples, an indent was made on the standard specimen,
and the sizes of the diagonals of the indents on tested samples were compared to
those made on the standard specimen by the diamond pyramid after production. In
the case that the sizes of the indent diagonals deviated from the initial value by
more than 3 %, the diamond pyramid was corrected. No fracture of the indenter
was observed during the hardness measurements under the indentation loads used.
The Raman spectra were measured using a Horiba Jobin Yvon T64000
spectrometer equipped with an Olympus BX41 confocal microscope. A discrete
emission line of an Ar–Kr laser (λexc = 514.5 nm) was used as the source of the
optical excitation. The laser beam was focused onto a sample at a site 0.2–0.5 μm
in diameter. The space spectral mapping of the sample was conducted by
displacing automated table at a step of 0.1 μm. The frequency of the spectral line
was accurate to 0.15 cm–1. The Raman spectra were measured in the center of the
CVD diamond samples.
The wear tests were conducted in cutting Korostyshev granite of the XI
drillability category on a special stand based on a DIP-200 screw–cutting lathe.
The Korostyshev granite is characterized by stable properties, high hardness, and
abrasivity. During the tests, a special equipment as a split cylinder and a sleeve for
fixing the rock core as well as a special workholder to fix the sample of a rock
destruction element in the machine toolholder (based on a drill chuck) were used.
The rock sample was fixed in the chuck of the special workholder, approached
to the rock core surface and was longitudinally cut at a set penetration depth.
To measure the wear loss of samples during the tests a Sartorius type balance
was used. The cutting parameters: rotation frequency – 355 r/min; penetration
depth – 0.25 mm. Parameters that were registered: deepening in penetration with
an accuracy of 0.05 mm; turning time accurate to 1 s.
The wear intensity I (mg/km) is defined as the ratio between the mass wear of
the rock destruction element Δm = min –mf to the drifting for a tool element L,
where min and mf (mg) are the sample masses before and after testing, respectively:
L
mI Δ= ; tDnL
60
π= ,
where D is the core diameter, km; n is the rotation frequency of the work spindle,
min–1; t is the cutting time, min.
www.ism.kiev.ua/stm 6
The comparative testing of samples were carried out at a cutting speed of
1.35 m/s, the length of turning 1180 m, turning time 870 s.
RESULTS AND DISCUSSION
Thermal weight loss
The weight loss of CVD diamond, PCD, and UHPCD after thermal treatment
are given in Table 1. It is shown that the thermal weight loss of CVD diamond is
larger than those of PCD and UHPCD. Furthermore, the weight loss rate of CVD
diamond is 25.0 %, which is 25 times bigger than that of the UHPCD. However,
little difference can be seen between PCD and UHPCD.
The CVD diamond easily loses weight under high temperature. The first reason:
a thermal decomposition of nondiamond phases is happened under high
temperature [7]. The other reason: it is supposed that the residual oxygen in the
furnace results in oxidation. The early stage of the oxidation process for CVD
diamond occurred preferentially at grain boundaries and local defects, due to the
substantial amount of sp2 bonded carbon present. It was reported that the oxidation
of sp2 bonded carbon is much easier than that of sp3 bonded carbon [8]. The atomic
oxygen reacts with CVD diamond at the surface and forms CO and CO2 products.
It means that most oxygen react with diamond at the surface of PCD. At the same
time, the sintering agent Si and SiC at the surface of PCD react with oxygen. These
products could increase the weight of PCD. Therefore, the weight loss of PCD and
UHPCD is lower than that of CVD diamond. Furthermore, the CVD diamond is
thoroughly exposed to the environment. It will have more chances to contact with
oxygen. Whereas the CVD diamond in UHPCD is surrounded by PCD, the size of
the area exposed to oxygen is small. It implies that the UHPCD protects CVD
diamond against the effect of oxidation.
Table 1. Thermal weight loss of CVD diamond, PCD and UHPCD
Weight, mg No. Sample
untreated thermal treated
Weight loss,
mg
Weight loss
rate, %
1 PCD 135.2 133.7 1.5 1.1
2 CVD 8.8 6.6 2.2 25.0
3 UHPCD 137.6 136.2 1.4 1.0
Hardness
Table 2 exhibits the hardness of CVD diamond in UHPCD. It can be seen that
the CVD diamond has a rather high initial hardness, which is 94±4 GPa. After
HP-HT, the hardness of CVD diamond in the UHPCD increases up to 140 GPa.
The increasing hardness of the CVD diamond results from the plastic deformation
of diamond grains during the formation around CVD diamond [5]. The hardness of
the CVD diamond in thermal treated UHPCD decreases from 133±7 GPa to
109±3 GPa while it is still higher than 94±4 GPa of the untreated UHPCD.
Table 2. Hardness of CVD diamond in UHPCD
Hardness of CVD diamond, GPa
untreated untreated UHPCD thermal treated UHPCD
94±4 133±7 109±3
ISSN 0203-3119. Сверхтвердые материалы, 2015, № 2 7
In the structure of diamond, sp3 orbitals contribute to formation of four C–C
bonds, which produce tetrahedral structure of diamond. Hardness of CVD diamond
usually varies over a wide range with sp3 to sp2 bonding ratio. The bonding ratio
depends on the kinetic energy of the carbon species and amount of hydrogen. It
was reported that the predominant defects were hydrogen clusters and nondiamond
impurity phases for the CVD diamond [9]. These defects usually produce some
local strain in the CVD diamond. Therefore, the strain distorts the atomic
arrangement in the diamond lattice. Hydrogen clusters or nondiamond phase react
with residual oxygen in the furnace, then the defects can be removed. The
weakened local strain and more normal atomics in the CVD diamond lattices could
be formed. Thus, the hardness of the CVD diamond decreases after the thermal
treatment.
Raman spectra
The Raman spectra of the samples exhibited a C–C single-phonon band of
vibrations near the 1332 cm–1 region, which is characteristic of carbon compounds
of the type of diamond with the sp3 chemical bond hybridization [10]. The full
width at half maximum (FWHM, Г) and wavenumber position (ω) of a Raman line
are compared. The FWHM is dependent on many complex factors such as
crystallite size or structural disorders [11]. When the crystal is subjected to
externally imposed stress or internal flaws caused stress, the position of the Raman
peak is subtly affected.
Raman spectra of CVD diamonds (untreated, untreated UHPCD, and thermal
treated UHPCD) are given in Table 3. It is shown that the peak position of CVD
diamond increases from 1333.3 to 1334.0 cm–1 and the FWHM increases from 9.3
to 12.7 cm–1 after HPHT treatment. A high value of the FWHM means a heavy
disordering of the CVD diamond material. The variations of the peak position and
FWHM point to the inhomogeneous distribution of elastic deformations and
perfection degree of the crystal structures of diamond. It has been found that the
broadened FWHM of the CVD diamond in UHPCD is evidently due to the
increase of the structural defect concentration [5].
Table 3. Raman spectra of CVD diamonds
Parameter CVD diamond Untreated UHPCD Thermal treated UHPCD
ω, cm–1 1333.3 1334.0 1332.9
Г, cm–1 6.4 10.9 6.8
The FWHM of CVD diamond in thermal treated UHPCD becomes narrower
than that of CVD diamond in untreated UHPCD. It is closer to natural and
synthetic diamond single crystals whose FWHM were only 2–2.5 cm–1[12]. The
FWHM reflects the degree of distortion [13]. The distortion in crystallographic
symmetry removes the Raman peak completely or partially. The strain weakens
after eliminating the defects. Meanwhile the distortion is less. It was reported that a
significant reduction of impurity phases in CVD diamond leads to an appreciable
reduction of the FWHM of Raman spectra [9]. It can be concluded that the
distortion of the CVD diamond in UHPCD becomes weaker after thermal
treatment.
The peak position decreases from 1334.0 to 1332.9 cm–1 after the thermal
treatment. The position of the Raman peak is affected by stress [14]. Compressive
stress results in a shift of the peak to higher frequencies, and tensile stress results in
www.ism.kiev.ua/stm 8
a shift of the peak to lower frequencies. The peak position decreases to 1332.9 cm–1,
but it is still higher than the theoretical position 1332.5 cm–1. The results showed
that the compressive stress is partly released after thermal treatment. But the crystal
in CVD diamond is still subjected to compressive stress. Hydrogen clusters or
nondiamond phases usually produce some strain and distort atomic arrangement in
the diamond lattice. They are removed after thermal treatment. Then the distortion
weakens. The compressive stress is released. Therefore, the peak position is shifted
to lower wavenumber.
Wear performances
The wear loss of the untreated and thermal treated UHPCD are shown in
Table 4. The average wear rate of the untreated UHPCD is 0.17 mg/km and of
thermal treated UHPCD the average wear rate is 0.6 mg/km. The thermal treatment
increases the wear loss of UHPCD. The wear resistance of thermal treated UHPCD
is better than that of PCD by a factor of 10.
Table 4. Wear loss of the untreated and thermal treated UHPCD
Weight, mg Sample Sample No.
initial final
Wear loss,
mg
Wear rate,
mg/km
Average wear
rate, mg/km
1 133.4 133.2 0.2 0.17 Untreated
UHPCD 2 135.4 135.2 0.2 0.17
0.17
1 130.6 129.8 0.8 0.53 Thermal treated
UHPCD 2 128.8 127.8 1.0 0.67
0.60
PCD 1 92.6 82.6 10.0 6.10 6.10
Discussion
The hardness of the CVD diamond in UHPCD decreases from 133±7 to
109±3 GPa after thermal treatment. At the same time, the wear resistance of the
thermal treated UHPCD is lower than that of the untreated UHPCD. The obtained
result is consistent with the result reported in [13]. Even though the CVD diamond
in our experiment and the CVD diamond material in [13] were not manufactured in
the same factory, they belong to the same kind of superhard materials.
Furthermore, there is a quasilinear relationship between the hardness and wear
resistance of diamond [15]. The narrowing of FWHM and downshift of Raman
peak are consistent with the decrease of hardness and wear resistance of CVD
diamond. The growth defects affect the hardness and wear resistance of the
UHPCD. Both the crystal structure defects and released compressive stresses in
CVD diamond result in the drop of the hardness after thermal treatment. Hydrogen
clusters and nondiamond carbon phases are removed under high temperature by
thermal decomposition and oxidation. The residual atomic oxygen reacts with
hydrogen clusters and nondiamond impurity phases at the surface of CVD
diamond. And then these kinds of defects are removed from CVD diamond. The
distortion about atomic arrangement in the diamond lattice weakens. The FWHM
of Raman spectrum reflects the degree of the crystal structure distortion. The
FWHM of CVD diamond is narrower after thermal treatment. It shows a decrease
of the structural defects in this material. A shift of the Raman peak is dependent on
the stress of the CVD diamond crystal. The strain in diamond lattice weakens after
removing the defects. And then the compressive stresses are released. Therefore,
the peak position moves to a lower wavenumber. Nevertheless, the UHPCD can be
recognized as a kind of materials with excellent heat durability and wear resistant
ISSN 0203-3119. Сверхтвердые материалы, 2015, № 2 9
performance. Based on the research of the UHPCD properties, the material could
be recommended for manufacturing drilling bits and dressing tools.
CONCLUSIONS
The following conclusions have been drawn from this study:
– after HPHT the hardness of CVD diamond inside the UHPCD increased by
41 %. Although after the thermal treatment the hardness of CVD diamond
decreased from 133±7 to 109±3 GPa, it was still higher than 94±4 GPa that of the
untreated UHPCD;
– the lower hardness of the CVD diamond in the thermal treated UHPCD
contributed to a higher wear rate. The wear rate of the UHPCD decreased from
0.17 mg/km to 0.6 mg/km after thermal treatment, but it was still much lighter than
6.1 mg/km that of the PCD;
– the narrowing of the FWHM and the downshift of Raman peak were implied
the lighter structural defects and released compressive stresses under high
temperature, which result in a drop of the hardness and wear resistance of CVD
diamond in thermal treated UHPCD.
ACKNOWLEDGEMENTS
The authors thank the National Natural Science Foundation of China
(51375466) and the International Science and Technology Cooperation Project of
China (2011DFR50060).
We are also grateful to Prof. Alexandr Shulzhenko, Dr. Alexandr Sokolov and
Vladislav Gargin from the Department of Synthesis and Sintering of Superhard
Materials, Bakul Institute for Superhard Materials, National Academy of Sciences
of Ukraine, for their help in synthesis and characterization experiments.
Досліджено термічну стабільність надтвердого полікристалічного ал-
мазного (UHPCD) композиційного матеріалу, отриманого армуванням полікристалічного
алмазу після хімічного осадження (CVD) алмазу в потоці аргону при 1200 °C. Для
порівняння твердості, C–C-структури і зносостійкості необробленого та термооброб-
леного UHPCD було досліджено заглиблення індентора, спектри комбінаційного
розсіювання та знос. Показано, що твердість CVD-алмазу в UHPCD досягає 133±7 ГПа
після дії високого тиску і високої температури, а після термообробки зменшується до
109±3 ГПа, зносостійкість UHPCD після термообробки зменшується від 0,17 до
0,6 мг/км. Звуження напівширини і зсув піку комбінаційного розсіювання в область низьких
частот CVD-алмазу в термообробленому UHPCD характеризує зменшення кристалічних
структурних дефектів і напружень стиску, що призводить до зниження твердості CVD-
алмазу в термообробленому UHPCD. Вища швидкість зносу термообробленого UHPCD
пов’язана з більш низькою твердістю.
Ключові слова: надтверді полікристалічні алмази, термостабільність,
CVD-алмази, зносостійкість.
Исследована термическая стабильность сверхтвердого поликристал-
лического алмазного (UHPCD) композиционного материала, полученного армированием
поликристаллического алмаза после химического осаждения (CVD) алмаза в потоке арго-
на при 1200 °C. Для сравнения твердости, C–C-структуры и износостойкости необрабо-
танного и термообработанного UHPCD были исследованы глубина проникновения ин-
дентора, спектры комбинационного рассеяния и износ. Показано, что твердость CVD-
алмаза в UHPCD достигает 133±7 ГПа после действия высокого давления и высокой
температуры, а после термической обработки уменьшается до 109±3 ГПа, износостой-
кость после термической обработки UHPCD уменьшается от 0,17 до 0,6 мг/км. Сужение
полуширины и сдвиг пика комбинационного рассеяния в область низких частот CVD-
алмаза в термообработанном UHPCD характеризует уменьшение кристаллических
структурных дефектов и напряжений сжатия, что приводит к снижению твердости
www.ism.kiev.ua/stm 10
CVD-алмаза в термообработанном UHPCD. Более высокая скорость износа термически
обработанного UHPCD связана с более низкой твердостью.
Ключевые слова: сверхтвердые поликристаллические алмазы, термо-
стабильность, CVD-алмазы, износостойкость.
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School of Engineering and Technology, Received 04.06.14
China University of Geosciences, Beijing
Key Laboratory of Deep Geo-drilling Technology
of the Ministry of Land and Resources, China University of Geosciences, Beijing
Beijing Huayou Guanchang Environment
and Energy Science & Technology Development Co., LTD, Beijing, China
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