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4-Sintering_PPT_powder metallurgy PMSC-2016.pptx
1. PMSC 17
POWDER METALLURGY SHORT
COURSE
Powder Metallurgy Association of India
24-27 September, 2017
Presentation
on
Sintering
by
Dr. N. B. Dhokey
Dept. of Metallurgy and
Materials Science
College of Engineering, Pune
1
2. What is Sintering?
• Sintering is a thermal
treatment for bonding
particles into a coherent,
predominantly solid structure
via mass transport events that
often occur on atomic scale
• The bonding leads to
improved strength and a lower
system energy
2
3. Basics of Sintering
• When thermal energy is applied to a powder compact, the compact
is densified and the average grain size increases, this phenomenon
is known as sintering.
• During sintering, the powder particles are bonded together by
diffusion and other atomic transport mechanisms, and the resulting
somewhat porous body acquires a certain mechanical strength
Before sintering After sintering
3
4. Brief History
• Sintering is, in fact, one of the oldest human technologies, originating in the prehistoric era
with the firing of pottery.
• Some of the first sintered products were bricks heated in open-pit fires to add strength.
• Other examples include gold-platinum jewelry sintered by Incas.
• During 19 th century chemically precipitated Pt powder was hot pressed to form dense
structures for the laboratory purpose.
• The production of tools from sponge iron was also made possible by sintering.
• The modern era of sintering is traced to Coolidge, who used tungsten powder to develop a
durable lamp filament for Edison.
• Nevertheless, it was only after the 1940s that sintering was studied fundamentally and
scientifically.
• Since then, remarkable developments in sintering science have been made. One of the most
important and beneficial uses of sintering in the modern era is the fabrication of sintered parts
of all kinds, including powder-metallurgical parts and bulk ceramic components
5. General fabrication pattern of sintered parts
• Powder Production
• Blending or Mixing
• Compaction
• Sintering
• Finishing
5
6. Goals in Sintering Studies
• Sintering preserves compact shape while bonding the particles to
one another, a process referred to as net-shaping.
• The ability to control product shape, properties and defects is
important to sintering.
• Sintered products are usually more precise than casting but less
precise than machined components.
• Where particles have high level of compressibility, sintering can be
performed at low temperature with zero dimensional change leading
to high precision.
6
7. Problems in sintering
• In industrial sintering operations , major concern is with processing
cost.
• Following issues needs attention
Reproducibility
minimized flaws
dimensional and compositional control
production efficiency
• Many sintering problems are introduced prior to entering the
sintering furnace
• Sintering tends to amplify or enlarge a defect
• Thus more attention is needed to detect problems early in processing.
7
8. Sintering Measurement Techniques
Density
• Percentage or fractional density gives evidence of fundamental
events occurring during sintering, independent of material.
• It is defined as measured density divided by theoretical density.
Vs = ρ/ ρT (ρT is theoretical or pore free density)
• It is determined by the Archimedes method using equation as stated
below
ρ = [Wair/ (Wair – Wwater)]. ρ water
8
9. Sintering Measurement Techniques
Other density measurement techniques
x-ray absorption
Magnetic resonance imaging
Small angle neutron scattering
Ultrasonic attenuation
Gamma-ray absorption
• These techniques give less resolution and are less direct.
• They are not frequently used to characterize the point to point
density changes induced by compaction or sintering.
9
10. Porosity
• Pores are inherent part of sintering
• They are present in the powder compact as interparticle voids
• Also during sintering pore can form from
Uneven phase distribution
Unbalanced diffusion events
Reaction with atmosphere
Capillary spreading of liquid upon melting
• The pore space is characterized by its amount, size, shape and
distribution throughout the compact
Porosity and pore characteristics
10
11. ……Porosity and pore characteristics
• Pore size, shape and connectivity are typical concerns during
sintering
• Size and shape of pores vary during sintering
• Initially pores are irregular later in sintering they form a smooth,
nearly cylindrical network
• The high density compact had small pores with a narrow size
distribution. It exhibits better sintering densification
• Alternatively low-density compacts shows few large pores
11
12. Variables affecting Sinterability and
Microstructure
• Variables Affecting Sinter
ability and Microstructure
Variables related to raw
materials(Material variables)
• Variables related to sintering
conditions(Process Variables)
• Powder:
Shape, size, size distribution,
agglomeration etc.
• Chemistry:
Composition, impurity, non-
stoichiometry, homogenity, etc.
• Temperature, time, pressure,
atmosphere, heating and cooling
rate, etc.
12
14. Sintering
• Often called (solid-state sintering, or solid-phase sintering)
because the metal remains unmelted
• The process whereby compressed metal powder (Green compact)
is heated in a controlled atmosphere furnace to a temperature
below melting point of at least one major constituent, but high
enough to cause bonding of the particles.
• Sintered density depends on its “green density” and sintering
conditions (temperature, time and furnace atmosphere).
• Sintering temperatures are generally within 70 to 90% of the
melting point of the metal or alloy.
• Held for sufficient time to permit bonding of the particles Times
range from 10 minutes for iron and copper to 8 hours for tungsten
and tantalum.
• Used for materials such as ceramics and cermets that cannot be
melted and cast by other methods.
16. 1. Solid state sintering
Only solid phases are present at the
sinter temperature
2. Liquid phase sintering
Small amounts of liquid phase are
present during sintering
3. Reactive sintering
Particles react with each other to new
product phases
Types of Sintering
20. Some parameters, such as the sintering
temperature, applied pressure, average
particle size and atmosphere can be
controlled with sufficient accuracy
Others, such as the powder characteristics
and particle packing are more difficult to
control but have a significant effect on
sintering
Parameters in Sintering
21. Atomic diffusion takes place and the
welded areas formed during compaction
grow until eventually they may be lost
completely
Recrystallisation and grain growth may
follow, and the pores tend to become
rounded and the total porosity, as a
percentage of the whole volume tends to
decrease
What happens during Sintering?
22. In the pressing operation the powder
particles are brought together and
deformed at the points of contact.
At elevated temperature - the sintering
temperature - the atoms can move more
easily and quickly migrate along the
particle surfaces (the technical term is
Diffusion)
What happens during Sintering?
23. Metals consist of crystallites
At the sintering temperature new crystallites
form at the points of contact so that the
original inter-particle boundaries disappear,
or become recognizable merely as grain
boundaries (This process is called
Recrystallisation)
What happens during Sintering?
24. The total internal surface
area of the pressed body is
reduced by sintering
Neck-like junctions are
formed between adjacent
particles as can be seen on
the adjoining scanning
electron micrograph
What happens during Sintering?
Neck formation between sintering copper spheres.
25. As with all processes, sintering is accompanied by an
increase in the free energy of the system. The sources that
give rise to the amount of free energy are commonly
referred to as the driving forces for sintering. The main
possible driving forces are
The curvature of the particle surfaces
An externally applied pressure
A chemical reaction
Driving Force for Sintering
27. Effects caused during sintering
• Chemical changes
• Dimensional changes
• Relief of internal stresses
• Phase changes
• Alloying
Sintering is a complicated process during which
physical, chemical and metallurgical effects interact.
28. First Stage
After burn out of any organic additives, two
things happen to the powder particles when
the mobility of the surface atoms has become
high enough; initially rough surface of the
particles is smoothened and neck formation
occurs
Stages of Sintering
29. Second Stage
Densification and pore shrinkage. If grain
boundaries are formed after the first stage,
these are new source of atoms for filling up the
concave areas which diminishes the outer
surface of the particle
Third Stage
Grain growth takes place, the pores break up
and form closed spherical bubbles
Stages of Sintering
32. Powder Compaction and Sintering
Sintering process
Sintering temperature range for iron-based alloys is
1100-1150°C and the time varies between 10 and 60
minutes, depending on the application.
33. In the late stage of sintering, volume diffusion is, no doubt, responsible for the
phenomenon of pore rounding. The sketch at Fig. 6.5a shows schematically how
vacancies migrate from the sharp corners to the flatter parts of the pore surface.
35. Six Stages of Sintering
Stage Phenomena Remarks
I 1 Initial bonding No shrinkage
I 2 Neck growth No shrinkage
II 1 Pore channel closure Densification begins
II 2 Pore rounding No shrinkage
III 1 Pore shrinkage (densification) Most important stage
III 2 Pore coarsening No further densification
37. Growth of neck width between
spherical particles during sintering (according
to a theoretical model by C.G. Kuczynski)
above : time law.
below : various mechanisms of material
transport.
38. • Improves the strength of the material
• Proper furnace control is important for optimum properties
39. Sintering of Nickel powder. The time
lapse photography illustrates Neck
formation and coarsening.
40. • Transforms compacted mechanical bonds to
much stronger metallic bonds.
• Shrinkage always occurs:
sintered
green
green
sintered
V
V
shrinkage
Vol
_
3
/
1
_
sintered
green
shrinkage
Linear
Sintering
3 important variables :
1. Atmosphere
2. Temperature
3. Time
42. Solid state sintering of heterogeneous material
Relationship between phase diagram and alloy formation
the growth rate of the
neck now depends not only on the
diffusion rates in the two pure metals but
also on the different diffusion rates in the
various alloy phases being formed in and
on either side of the neck.
On the other hand, the neck width
controls the rate of alloy formation.
43. • Metallurgical bonding of powder particles
by solid state diffusion or Liquid phase
• Thermal activated event such as atomic
transport, particle rearrangement or
particle growth occur.
• Vapor-phase transport – heated very
close to melting temperature allows
metal atoms to release to the vapor phase
• Resulting in densification, yield useful
physical properties (UTS, YS, ductility,
and fatigue strength)
Sintering
Mechanical
Properties
3-Stages for a typical sintering process
52. Two sphere model
r
r1
r2
The neck has a negative curvature
component (-1/ρ), acting to reduce the
pressure relative to the spherical surface.
P
1
r
1
P
1
r 1
1
r 2
55. Solid state sintering
• Solid state sintering occurs when the powder compact is densified
wholly in a solid state at the sintering temperature
• Sintering forms solid bonds between particles when they are heated
• With extended heating it is possible to reduce pore volume leading
to compact shrinkage although in many sintering systems
dimensional change is undesirable
• Sintering is done at homologous temperature. This temperature
depends on the material and particle size
• Homologous temperature is absolute sintering temperature divided
by absolute melting temperature.
• Most materials exhibit sintering at homologous temperature between
0.5 and 0.8.
55
56. Basic Mechanisms of Sintering
Solid state sintering of homogeneous material
• Surface diffusion
• Volume diffusion (migration of vacancies)
• Grain-boundary diffusion
• Viscous or plastic flow (caused by surface
tension or internal stresses)
• Evaporation-condensation of atoms on
surfaces
• The vacancy transport , accumulation and
annihilation events are key to sintering
behavior 56
57. Basic Mechanism of Sintering
• Surface diffusion: The vacancies and atoms move along particle surfaces
• Evaporation-condensation: across pore space
• grain-boundary diffusion: move along grain boundaries
• volume diffusion: Through lattice interior
57
60. Initial stage of sintering
• Local point of contact formation or "fusion", without shrinkage of compact. This is
accompanied by smoothing of the free surface of particles
• Neck formation at the contact point, with the resulting concave curvature δn (where
δn=1/rn) at the neck, in contrast to the convex curvature on the particle surface of
radius r, where r >> r n. The two radiuses of the neck curvature, r n and y, represent
an experimental justification for the two-sphere model of sintering.
• The processes 1A and 1B result in densification of the sintering component by ~10%.
That is, if the relative green density after forming of the particle compact was 60%,
the density after initial stage would be about 70% of the theoretical density TD.
However, the 10% densification in the initial stage is reached very quickly (seconds
or minutes) after exposing powder to high temperature, because of the large surface
area and the high driving force for sintering
60
62. Intermediate stage of sintering
• neck growth
• pores forming arrays of interconnected cylindrical
channels
• particle centers approaching one another, with the
resulting compact shrinkage
• The shrinkage in the intermediate stage can result
in additional densification by as much as 25%, or
to a total of about 95% of the TD (theoretical
density). However, shrinkage does not necessarily
have to take place during the intermediate stage of
sintering. For example, shrinkage would not occur
if matter was transported FROM the particle
SURFACE, and proceeded through either gas, solid
or along interface as surface diffusion
62
63. Final stage
• Isolation of pores, i.e. relative density
exceeding ~93%
• Elimination of porosity
• Grain growth
• The final sintering stage begins at about 93-
95% of theoretical density, when porosity is
already isolated. Ideally, at the end of this
stage all porosity is eliminated. The complete
elimination of porosity in the final stage of
sintering can only happen when all pores are
connected to fast, short diffusion paths along
grain boundaries (or, equivalently, if the grain
boundaries remain attached to the pores)
63
64. Solid state sintering
examples
Lucalox alumina, after a) compaction, b) 1, c) 2.5, and d) 6
min. @1700°C Distaloy AE + 0.5% C after sintering for (a) 30
minutes, (b) 4h and (c) 16h,
respectively at 1120°C.
Ceramics :
Alumina
Metal :
Distaloy AE +
0.5% C
64
66. Solid state sintering
• Solid state sintering of homogeneous material Judging by the changing shape of the
interspace between sintering particles
• the sintering process passes through two different stages:
1) an early stage with local bonding (neck formation) between adjacent particles, and
2) a late stage with pore-rounding and pore shrinkage.
• In both stages, the bulk volume of the sintering particles shrinks – in the early
stage, the center distance between adjacent particles decreases, in the late stage, the
total pore volume shrinks
Microstructure of Astaloy Mo + 0.4% C sintered at
1120°C for 30 minutes;
cooled from 1120°C at (a) 0.25°C/s (f) 56°C/s.
Sintered ferritic unalloyed
powder steel
66
67. Liquid phase sintering
• liquid phase sintering occurs when a
liquid phase is present in the powder
compact during sintering
• The formation of liquid phase during
sintering usually increases the
sintering rate
• Liquid phase sintering is traced to the
development of cemented carbides,
bronze bearings magnetic alloys and
tungsten heavy alloys (W-Ni-Fe)
• When surface energies are dominant,
liquid-phase sintering densification
occurs in stages as shown in fig. Conceptual outline of changes associated with solution
reprecipitation densification where both grain growth and
grain shape accomodation act to release liquid to fill
residual pores
67
68. Liquid phase
sintering
W-Ni-Fe hold at
1500°C for 0 min
W-Ni-Fe hold at
1500°C for 30 min
A schematic of the microstructure changes during LPS
68
70. Examples of the microstructure variation with composition
changes, where the white corresponds to copper (liquid) and
the dark corresponds to cobalt (solid) ranging from 30 to 80%
cobalt
General Requirements
for Liquid Phase
Sintering
•An appreciable amount of
liquid must be present
• Solubility of solid in a liquid
•Wetting of the solid by the
liquid
70
71. Transient liquid-phase sintering
A liquid is formed when the compact is heated to the sintering
temperature.
The liquid is transformed into a solid by interdiffusion while the
compact is at the sintering temperature, such as in the sintering of
compacts from mixtures of copper and tin powders, in which an
alpha bronze solid solution is formed.
71
72. • Pressure assisted sintering increases the contact pressure of particles and
thus the driving force for sintering compared to pressure less solid state
sintering
• by ~ one order of magnitude in hot pressing (HP) at 20-40 MPa pressure
• by ~ two orders of magnitude in hot isostatic pressing (HIP) at 200 -300
MPa pressure
Pressure assisted Sintering -Technology
72
73. Hot isostatic pressing
• Hot‐isostatic pressing (HIP) combines powder
compaction and sintering into a single operation
• Gas‐pressure squeezing at high temperatures
• Heated powders may need to be protected from
harmful environments
• Products emerge at full density with uniform,
• isotropic properties
• Near‐net shapes are possible
• Produces compacts with almost 100% density
• Good metallurgical bonding between particles
and good mechanical strength
Etched microstructure of glass
encapsulation HIP Ti-6Al-4V
73
74. Uses
• Superalloy components for aerospace
industries
• Final densification step for WC cutting
tools and
• P/M tool steels 74
75. 75
Pressure Assisted Sintering -Technology
Hot Pressing
Apart there are hot consolidation techniques of metal
powders, where sintering and densification are
combined by applying pressure to the powder at
elevated temperature.
External Heating
• The simplest form of pressure-assisted sintering is
that which occurs by uniaxial hot pressing. A
refractory mold (die) is inserted into a furnace, and
both the powder and the die are heated while the
punches are driven by an external pressure source.
Internal (Resistance) Heating
• Resistance heating means the heavy current passes at
low voltage through the job for certain time, thus
enabling the job to be heated upto required
temperature for subsequent heat treatment.
• The heat generated in the job owing to its resistance
to the flow of current.
External Heating
Internal Heating
76. Hot pressed WC
Fig. 12. Changes in microstructure of sintered samples (a) WC-7.5wt%Co at 1
GPa, (b) WC-7.5wt%Co at 3 GPa, (c) WC-12wt%Co at 1 GPa and (d) WC-
12wt%Co at 3 GPa.
76
77. Spark Plasma Sintering
• Formation of small capacitors at the contact between particles/ at gap around the contact.
• Electrical discharges are generated across these capacitor gaps. The interfering surface oxide films
are pierced beyond a certain voltage level, depending on the dielectric strength of oxide layer. This
takes place when the arcing across the particles leads to achieving the break down voltage and
electrical break down of dielectric film on the powder particle surface.
• Alternatively, the electrical discharges around the contacts may generate plasma, that is, an ionized
gas between the powder particles.
• The above phenomena collectively contribute to the physical activation of the powder particle
surface. The physical activation combined with faster densification at lower temperatures reduces
grain coarsening and retains a finer microstructure.
ON-OFF pulsed current path
through the powder
77
78. Phenomenology of SPS:-release of electrical energy through a porous powder compact -breakdown
of surface films-Arcing at pores leading to enhanced mass transport to neck
Uses
All types of materials, even those difficult - to- densify can be
easily sintered in SPS.
78
79. SPS sintering steps
SEM micrograph of the HA-
YSZ composite prepared by
spark plasma sintering at 1200
ºC for 5 min
Initial state Expansion Start of neck formation
Optical micrographs of MoSi2 samples sintered at 1400°C
(right: SPS, left: Hot pressing) (polarized light).
Composite
Ceramic
79
80.
⊙
⊙
⊙
⊙
⊙
⊙
⊙
⊙
⊙
⊙
P
P
Heater
Comparative Study: Spark Plasma
Sintering vs. Hot Pressing
P
P
DC pulse
Joule heating by applying
on-off DC pulse
Heating by heater located
outside of mold
• In SPS the powder is directly fed into the graphite dies and the
die is enclosed with suitable punches.
• This entire assembly is directly put into the SPS chamber and spacers are used if
necessary.
•he chamber is now closed and the atmosphere (vacuum, Argon etc) in which
sintering is to be carried out is applied in the chamber. 80
81. Fig. 1 Assisted effects of sintering for pressure sintering: (a) Internal heating type of
spark plasma sintering; (b) External heating type
of hot pressing; (c) Internal heating type of electrical resistance sintering
Spark Plasma Sintering vs. Hot Pressing
81
82. Microstructure: HIP, SPS, ERS
82
WC6Co sinter-HIP
WC6Co SPS
WC6Co ERS
• In the three cases the
microstructure is quite similar
• polygonal WC grains can be
appreciated surrounded by Co
metallic matrix.
• Nevertheless, it seems to be
a slight grain refining as the
duration of the sintering
process decreases, from the
longer duration process to the
shorter one: Sinter-hip (3A),
SPS (3B) and ERS (3C).
83. 83
Hardness of Ti powders with different particle sizes by various sintering methods
Mechanical properties of WC-6Co sintered by three different techniques
Mechanical Properties: HIP, SPS, ERS
1. Titanium
2. WC-6Co
84. Laser Sintering
• Laser sintering produces 3D parts by sintering
together the successive layers of powder
material.
• One of the major advantages is that it is able to
process a very wide range of materials (standard
polymers, metals, ceramics, etc.)
• Complex shapes can be modeled and developed
within a very short period.
• Metals are more difficult to be laser-sintered
than the polymer materials. common problems
such as oxidation, balling and shrinkage may
result in low density, weak strength and rough
surface, of the sintered parts.
Surface morphology of the DMLS material,
500 ×, SEM. (a) Topview normal to building
direction with small cracks running over the
surface due to thermal shock. (b) Side-view
parallel to building direction with layers
piled up from the left to the right
Side view of the DMLS
material shows the wavy
layers, the hatching width
and the layer thickness
84
85. RP Technologies
• Sintering is carried out by various RP technologies.
Fig.: Schematic representation of rapid manufacturing of metal components by
layer manufacturing techniques.
85
86. RP Technologies
Fig.: Schematic representation of rapid manufacturing of metal components by
layer manufacturing techniques. 86
88. Advantages of Laser Sintering
• Any powder which can be sintered or will bond without melting can be used.
• The materials are nontoxic.
• It does not usually require support structures.
• The accuracy is in the range ±0.05–0.25 mm.
• It has fairly good speed around 12–25 mm/h.
• Wax models can be built in a few hours and used to make functional prototypes
by investment casting.
• It is a fully automatic process.
• Complex parts can be manufactured.
88
89. Disadvantages of Laser Sintering
• Part accuracy depends on size and complexity.
• The surface finish is rough, the article is porous and hence of poor
mechanical strength.
• The equipment is expensive.
• Cavities are difficult to clean since the powder tends to cling and bead
blasting is difficult in confined regions.
• Shrinkage can create serious residual stresses which can cause distortion or
cracking.
• Temperature control is critical.
• Processing is best done in an inert atmosphere to avoid oxidation, fire or even
explosions.
89
90. Applications
Mould inserts fabricated by the
direct laser sintering
Injection parts
Oil pump by direct laser
sintering
Die model for bevel gear forming
by nickel-based alloy powder
(a) Titanium model and (b)
original for medical
application
(a) As-formed and (b)
polished model of dental
crown produced
90
91. Microwave Sintering
Application of microwaves for sintering of the pure metal powder in powder metallurgy
process has been emerged as a potential process.
The microwave sintering has significant advantages over conventional sintering because of
different diffusion mechanism involved in it.
The smoother surface of powder compact is developed in short time by microwave sintering
than conventional sintering
91
93. Microwave sintering of ceramics, composites
and metallic materials
• Many traditional and advanced ceramics and composites have
been fabricated using microwave technology with potential of
saving time and energy.
• Ceramics: multilayer ceramic capacitors
93
94. Application of Microwave for Sintering of Metal
Powders
• Tungsten Powder
tungsten powder activated by high-energy milling
(HEM)
microwave sintered (at 2073 K with 1 hour soaking)
• Copper Powder
study of thermal profile of copper metal powder was
done when the material is exposed to 2.45 GHz
microwave radiation
The temperature variation with time of exposure
depends upon the particle size and initial porosity
• Aluminum Powder
Commercial Al powder was exposed to microwave
radiation for 45 min
microwave treated Al powder confirmed the formation
of Al–α- Al2O3
Temperature measured was 1000±10°C after 45 min
microwave heating of the Al powder
94
96. References
1. Randall M. German, Sintering Theory and Practices, pp. 1-230.
2. Je-ha SHON, Jong-moon PARK, Kyeong-sik CHO, Jae-keun HONG, Nho-kwang
PARK, Myung-hoon OH, Effects of various sintering methods on microstructure
and mechanical properties of CP-Ti powder consolidations, Trans. Nonferrous
Met. Soc. China 24(2014) s59−s67.
3. Randall M. German, Pavan Suri, Seong Jin Park, Review: liquid phase sintering, J
Mater Sci (2009) 44:1–39
4. Dinesh Agrawal, Microwave Sintering of Ceramics, composites and Metallic
Materials, and Melting of glasses, Transactions of the Indian Ceramic society, 129-
144.
5. Metals Handbook, Vol.4, 9.Edition, ASM, 1981
6. Distaloy and Starmix, Production of iron and Steel Powders, 2-20.
7. A.R. Olszyna, P. Marchlewski, K.J. Kurzydowski, Sintering of high-density, high-
purity alumina ceramics, Ceramics International 23 (1997) 323-328
96
97. References
8. Arunachalam Lakshmanan, Sintering of Ceramics – New Emerging Techniques, 1-24
9. Salvatore Grasso, Johannes Poetschke, Volkmar Richter, Giovanni Maizza,Yoshio Sakka
and Michael J. Reece, Low-Temperature Spark Plasma Sintering of Pure Nano WC
Powder, J. Am. Ceram. Soc.,1–4 (2013)
10. M. Suárez, A. Fernández, J.L. Menéndez, R. Torrecillas, H. U. Kessel, J. Hennicke, R.
Kirchner and T. Kessel, Challenges and Opportunities for Spark Plasma Sintering: A
Key Technology for a New Generation of Materials
11. J. Schmidt, T. Weissgaerber, T. Schubert, B. Kieback, Spark Plasma Sintering of
Intermetallics and Metal MatrixComposites, Euro PM2005 Sintering II, 93-98
12. J.M. Gallardo, J.M Montes, Th. Schubert, T. Weissgaerber, C. Andreouli, V
Oikonomou3, L.Prakash, J.A. Calero, G. Abrivard, C.Guraya, M.A. Lagos, I.Agote,
Preliminary Comparison of Hardmetals Obtained by SPS and by Electrical Resistance
Sintering (ERS) , Euro PM2014 - Hardmetals
97
