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International Days in Critical Raw Materials 25-26th June 2015, Burgos, Spain
Cobalt substitution in PCD cutting tool materials
Piotr Klimczyk1, Lucyna Jaworska1, Magdalena Szutkowska1,
Sławomir Cygan1, Maciej Sitarz2
1Institute of Advanced Manufacturing Technology, Poland
2AGH University of Science and Technology, Faculty of Materials Science and
Ceramics, Poland
International Days in Critical Raw Materials 25-26th June 2015, Burgos, Spain
Reliable material for cutting inserts
high: • hardness,
• wear resistance,
• flexural strength,
• fracture toughness,
• thermal stability,
• thermal shock resistance,
• thermal conductivity,
• chemical stability,
low: • coefficient of thermal expansion,
• coefficient of friction.
Introduction material properties
http://www.tungaloy.co.jp
International Days in Critical Raw Materials 25-26th June 2015, Burgos, Spain
Introduction diamond, a metastable allotrope of carbon
Diamond has the highest hardness and
thermal conductivity of any bulk material
The oxidation process occurs during heat
treatment of diamond in oxygen at
elevated temperatures
International Days in Critical Raw Materials 25-26th June 2015, Burgos, Spain
Polycrystalline diamond PCD is a two phase product in which the diamond crystals
are sintered together in the presence of metal catalyst phase
Introduction PCD materials
Cobalt belongs to the iron group of
materials, which are known to be
good solvents/catalysts for diamond
synthesis and also for the binder
phase during the diamond powder
sintering process.
Unfortunately, cobalt belongs
also to the group of critical raw
materials.
International Days in Critical Raw Materials 25-26th June 2015, Burgos, Spain
Introduction PCD materials
Sintered polycrystalline diamond
compacts (PCD) are widely used for:
• cutting tools
• wire drawing dies
• and rock drill bits
cutting brazing finishing
sintered compact
final product
International Days in Critical Raw Materials 25-26th June 2015, Burgos, Spain
The aim diamond based materials with high thermal resistance
and without CRM
Typical PCD cutting tool
material
Innovative PCD
composite
WC (~90%) + Co (~10%)
substrate layer
PCD +
Co (12 - 18%)
working layer
no substrate layer necessary
AMBITION: down to 0% WC, 0% Co)CRM (WC, Co)
substitution
Cobalt promotes graphitisation of diamond and decreases thermal stability
of sintered PCD parts (e.g. cutting tools)
One of the possibilities to increase the thermal resistance of PCD materials
is to reduce the cobalt bonding phase content
International Days in Critical Raw Materials 25-26th June 2015, Burgos, Spain
Starting powders
• diamond (Element Six, Micron+MDA, 3-6 µm,)
• titanium diboride (American Elements, <100 nm )
• cobalt (ABCR, 0.5-1.5 µm)
Preparation of material for sintering
• mixing: Planetary mill PULVERISETTE 6,
WC grinding balls φ 5 mm, acetone, 200 rpm / 2h,
• drying,
• compaction: manual hydraulic press, ~200 MPa,
discs φ 15 x 5mm
Experimental details samples preparation
diamond + 10% TiB2 diamond + 5% TiB2 + 2% Co
International Days in Critical Raw Materials 25-26th June 2015, Burgos, Spain
High pressure hydraulic press equipped with Bridgman’s type toroidal anvils
pressure up to ~8 GPa, temperature up to ~2400 °C,
duration of typical sintering process ~1 min
Experimental details HPHT sintering
International Days in Critical Raw Materials 25-26th June 2015, Burgos, Spain
Sintering batch
assemble
1 – ceramic gasket (outside part)
2 – ceramic gasket (inside part)
3 – ceramic disc
4 – molybdenum disc
5 – sample
6 – graphite disc
7 – graphite tube
8 – thermocouple (only for T-calibration)
Experimental details HPHT sintering
International Days in Critical Raw Materials 25-26th June 2015, Burgos, Spain
Pressure distribution in the sample during
plastic deformation of gasket in Bridgman's
anvils system
Experimental details HPHT sintering
International Days in Critical Raw Materials 25-26th June 2015, Burgos, Spain
0 10 20 30 40 50 60 70 800
1
2
3
4
5 P (Power of heating)
T [s]
P [
kW
]
0
1
2
3
4
5
R (Resistance)
R
Sintering process takes only one minute !!!
Experimental details HPHT sintering
International Days in Critical Raw Materials 25-26th June 2015, Burgos, Spain
Sample in the gasket before sintering
Sample in the
gasket after sintering
Sintered
compact
(raw
sample)
Sintered
compacts
after grinding
process
Experimental details HPHT sintering
International Days in Critical Raw Materials 25-26th June 2015, Burgos, Spain
Results microstructure
Diamond – TiB2 – Co composite: SEM image and X-ray maps of C, Ti and W
International Days in Critical Raw Materials 25-26th June 2015, Burgos, Spain
Results microstructure
Diamond – Co (commercial): SEM image and X-ray maps of C, Co and W
International Days in Critical Raw Materials 25-26th June 2015, Burgos, Spain
Results physical and mechanical properties
Composition
wt.%
Density
g/cm3
Hardness
GPa
Young’s
modulus
GPa
diamond + 10% TiB2 3.38 ±0.01 45.4 ±2.4 552 ±14
diamond + 5% TiB2 + 2% Co 4.04 ±0.01 66.6 ±2.9 834 ±23
diamond + 10 Co + 2 WC
(commercial) 4.14 ±0.01 78.6 ±13 976 ±34
International Days in Critical Raw Materials 25-26th June 2015, Burgos, Spain
Investigations tribological tests
Ball-On-Disc: coefficient of friction
Fn - applied normal force (load)
Ff - measured friction force
• ball material: Al2O3
• ball diameter: 3.175 mm
• applied load: 4 N
• sliding speed: 0.1 m/s
• radius of the sliding circle: 4 mm
• sliding distance: 200 m
• number of cycles: ~ 8 000
n
f
F
Fμ
International Days in Critical Raw Materials 25-26th June 2015, Burgos, Spain
Investigations tribological tests
Friction coefficient of diamond – TiB2 composite during sliding against Al2O3 ball
at 25, 200, 400, 600, 700 and 800 °C
International Days in Critical Raw Materials 25-26th June 2015, Burgos, Spain
Investigations tribological tests
Friction coefficient of diamond – TiB2 – Co composite during sliding against Al2O3 ball
at 25, 200, 400, 600, 700 and 800 °C
International Days in Critical Raw Materials 25-26th June 2015, Burgos, Spain
Investigations tribological tests
Friction coefficient of diamond – Co commercial material during sliding against Al2O3
ball at 25, 200, 400, 600 and 700 °C
International Days in Critical Raw Materials 25-26th June 2015, Burgos, Spain
Investigations hardness
Hardness of diamond composites as function of heat treatment temperature (air atmosphere)
International Days in Critical Raw Materials 25-26th June 2015, Burgos, Spain
Investigations XRD
XRD pattern of diamond - TiB2 composite after HPHT sintering
and after HT tribotests
International Days in Critical Raw Materials 25-26th June 2015, Burgos, Spain
Conclusions
• Diamond with 10 wt.% of TiB2 and diamond with 5% TiB2 and 2% Co
composites were sintered using HPHT apparatus under the pressure of
8GPa at the temperature of 2000°C. The composites were compared with
PCD commercial material
• The composites are homogeneous – their ingredients are uniformly
distributed in the volume of material
• The friction coefficient of all materials is the lowest (0.1 – 0.3) at lower
temperatures and rise up to about 0.7 – 0.8 at highest temperatures
• RT mechanical properties of diamond composites are lower
in comparison with PCD commercial material
• Diamond composite with addition 5% TiB2 and 2% Co is the most
resistant to the hardness changes at elevated temperatures. This material
maintains the high hardness value up to 800°C
International Days in Critical Raw Materials 25-26th June 2015, Burgos, Spain
Development of a sintering center and know-how
exchange for non equilibrium sintering methods
of advanced ceramic composite materials” – SINTERCER
REGPOT-2012-2013-1 EU FP7 Research Potential
SINTERCER - project no. 316232
duration: 01.06.2013 - 31.11.2016
The research activities carried out by
Institute of Advanced Manufacturing
Technology scientists are supported by the
European Commission under the FP7
Specific Programme 'Capacities'