A1262052002tfgAB

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MECHANICAL ALLOYING ASPECTS OF ODS ALLOYS Dr. R.
Vijay, S. Sudhakar Sharma and Dr. A. Venugopal
Reddy International Advanced research Centre
for Powder Metallurgy New Materials
(ARCI) Balapur, Hyderabad Tel [phone] Fax
040-244 2699 Email vravula_at_gmail.com
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ARCIs MANDATE

• Development of High Performance Materials and
  Processes for niche market
• Demonstration of Technologies at Prototype/Pilot
  Plant Scale
• Transfer of Technologies to the Indian industry

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CENTRES OF EXCELLENCE WITHIN ARCI (Technical
Groups)
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THRUST AREAS AT ARCI

• Nanomaterials
• Engineered Coatings
• Ceramics Processing
• Laser Processing of Materials
• Fuel Cells

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Spray pyrolysis
Microwave plasma synthesis
Levitating liquid drop
Nanomaterial Synthesis Production facilities at
ARCI
Electric explosion of wire
Planetary ball mill
Chemical methods
Precipitation
Combustion
Sol-gel
Aerogels
coatings
Attritor
Chemical vapour synthesis
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Cold iso-static press (4000 bar)
Hydraulic press (1500 tons)
Post Processing facilities
Rate controlled sintering
Coatings ? Detonation Spray Coating ? Cold
spray coating ? Laser ablation
Spark plasma sintering
Microwave sintering
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MECHANICAL ALLOYING (MA)
MA has been an area of strength at ARCI

• First developed over 40 years ago for production
  of dispersion strengthened alloy powders (Ni
  based super alloys for gas turbine application).
• Repeated welding, fracturing and rewelding of
  powder particles in high energy ball charge.
• Alloying is effected by the ball-powderball
  collisions in several stages.

R. Sundaresan and F.H. Froes, J. Metals, Vol. 39,
No. 8 (1987) 22-27
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MECHANICAL ALLOYING (MA)
Particle size variation with milling time during
MA
C. Suryanarayana, Progress in Mat. Sc., 46 (2001)
1-184
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MECHANICAL ALLOYING (MA)
Important milestones 1981 Development of ODS
nickel base alloys 1982 Amorphisation of
intermetallics 1983 Disordering of ordered
compounds 1987/88 Amorphisation of blended
elemental powder mixtures 1989 Synthesis of
nanocrystalline phases 1989 Synthesis of
quasicrystalline phases 1995 Hydrogen storage
materials 2003 High performance materials
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MECHANICAL ALLOYING (MA)
Growth rate of publications in MA
C. Suryanarayana, Progress in Mat. Sc., 46 (2001)
1-184
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MECHANICAL ALLOYING (MA)
MA is carried out in ? Shaker mills such as
Spex mill (few grams) ? Planetary mills such
Fritsch mill (0.1 to 0.5 kg) ? Attritors (0.5 to
100 kg) ? Conventional ball mills having dia gt 2
Mt with speed just below Nc
Process variables ? Type of mill ?
Milling atmosphere ? Milling container ?
Process control agent ? Milling speed ?
Temperature of milling ? Milling time ? Type
and size of grinding medium ? Ball to powder
weight ratio ? Extent of filling the vial
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MECHANICAL ALLOYING (MA)
MA Facilities at ARCI

• Maximum Speed 350 rpm
• 4 milling vials can be loaded.
• Quantity of powder 50-100 g/vial

Planetary Ball Mill
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MECHANICAL ALLOYING (MA)
MA Facilities at ARCI

• Maximum Speed 400 rpm
• Quantity of powder 1 kg/batch

Attritor
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MECHANICAL ALLOYING (MA)
MA Facilities at ARCI

• Maximum Speed 800 rpm
• Quantity of powder 1 kg/batch

Simoloyer
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MECHANICAL ALLOYING (MA)
Simoloyer Technology
The milling time to get the equal particle size
and grain structure is 10 times less than attritor
Particle Size Attritor 40 h 29 ?m Zoz 4
h 31 ?m
Grain size from XRD Attritor 40 h 20 nm
Zoz 4 h 15 nm
SEM of Zoz 4 h
SEM of Attritor 40 h
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MECHANICAL ALLOYING (MA)
Materials Developed using the existing facilities

• Mechanical Alloying
• Hydrogen storage Materials like FeTi, Mg2Ni
• High Energy Milling
• ODS materials
• Ultrafine WC-Co powders for cutting tools
• Fe-SiC powders for coating applications
• Nano aluminium powder
• Nanostructured Mg based composites for hydrogen
  storage
• Reactive Milling
• Nanostructured TiC from TiO2 and C
• Nanostructured WC and W2C from WO3 and C

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ODS MATERIALS

• Development of suitable clad material is
  essential for achieving high burn-up of fuel in
  Fast Breeder Reactors.
• Austenitic stainless steels swell significantly
  beyond
• 120 dpa
• Conventional Ferritic/Martensitic steels possess
  high swelling resistance ( lt 2 swelling upto 200
  dpa) compared to Aust. SS
• Ferritic steels posses poor thermal creep
  strength above 550oC
• ODS alloys serve as one of the alternatives with
  the potential of having advantage of ferritic
  steel and able to push operating temperatures to
  650oC and beyond.

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ODS MATERIALS

• APPLICATIONS
• Clad tubes of fast breeder reactor
• Structural material for advanced breeding
  blankets replacing EUROFER in fusion reactors
• Structural materials (joints) replacing reduced
  activation ferritic-martenstic steels (RAFS) in
  fusion reactors
• Backbone material for gas cooled divertor
  concepts in fusion reactors

• ADVANTAGES
• High operating temperature of 650-700?C
• Increased creep resistance High yield strength
• Resistance to swelling under irradiation

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ODS MATERIALS
Why ODS ?

• Precipitation hardening will be lost in ferritic
  steels over 650?C
• Oxide dispersion strengthening will be effective
  even over 700?C

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Requirements for ODS steels
High Temperature ? 750?C Long term service ? 9 Y
Creep Tensile Properties
Displacement damage ? 250 dpa
Radiation resistance (Dimensional stability)
Exposure to high burn up Fuel flowing Na
Chemical compatibility
Targetted Mechanical Properties

• Ultimate Tensile Strength (UTS) ? 300 MPa _at_
  700?C
• Internal creep rupture strength ? 120 MPa _at_
  700?C for 104 h
• Uniform elongation (UE) ? 1

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ODS MATERIALS
Tensile Property
Uniform elongation of both 9Cr-ODS and 12Cr-ODS
steels are comparable with SS316 and FMS.
Ultimate tensile strength of 9Cr-ODS steel is
much higher than precipitation hardened FMS.
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ODS MATERIALS
Creep Rupture Properties
Creep rupture strength of both 9Cr- and 12 Cr-ODS
steels under internal pressures meet the target
120 MPa for 10,000 h at 700?C
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ODS MATERIALS
Manufacturing Process
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ODS MATERIALS
Manufacturing Process
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ODS MATERIALS
Summery of Alloying Effects
Improvement Degradation
Cr Corrosion resistance ( 12 wt) - Irradiation/thermal embrittlement - ? ferrite in martinsite
W High temperature strength (Solution hardening) (Finer precipitation of M23C6) - Irradiation/thermal embrittlement - Laves, ? ferrite in martinsite
Ti High temperature strength (ODS) (Dispersoid morphology) - Non equilibrium phase generation Tube manufacturability (Microstructure controllability)
Y2O3 High temperature strength (ODS) (Dispersoid morphology) - Non equilibrium phase generation Tube manufacturability (Microstructure controllability)
EX. O High temperature strength (ODS) (Dispersoid morphology) - Non equilibrium phase generation Tube manufacturability (Microstructure controllability)
Ex. O is the most important alloying effect but
its effect is not well clarified
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ODS MATERIALS
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ODS MATERIALS
Experimental
To understand the effect of Ti on Ytrria
distribution in the iron matrix, the following
experiments are devised

• Fe-0.35Y2O3 2. Fe-0.21Ti-0.35Y2O3
• Particle size of Y2O3 1.3 ?m and 10-20 nm
• Composition milled in an attritor Fe-0.21Ti-0.35Y
  2O3

Milling Parameters Type of Mill Planetary
Mill/Attritor Ball to Powder ratio 151 RPM
250/300 Milling atmosphere Argon Time Up
to 40 h The samples were analysed for particle
size, XRD, SEM and hardness
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ODS MATERIALS
Particle size and Microhardness
Micro hardness with milling time
Particle size with milling time
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ODS MATERIALS
SEM Images of milled powder
Fe-Y2O3
Fe-Ti-Y2O3
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ODS MATERIALS
TEM Images SAD of Fe-Ti-Y2O3
SAD analysis showed the following
composition FeTiO2Y2O3Y2Ti2O7
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ODS MATERIALS
FESEM Images of sintered samples
The milled powders were double compacted and
double sintered at 1120?C for 2 h under hydrogen
atmosphere
Fe-Y2O3
Fe-Ti-Y2O3
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ODS MATERIALS
Canning, Degassing and Sealing

• Powder to be loaded in cans, evacuated and
  degassed, and weld sealed

Powder Feeding Facility
Canning facility
Sealed Cans

• Degassing temperature and evacuation time is the
  key to get good density in the extruded rod

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ODS MATERIALS
Consolidation of MA powders
Extrusion trials

• 250 ton hydraulic press with tooling for
  extrusion, 50 mm dia heated container, dies for
  selected extrusion ratios

Extrusion facility
Extruded rods
Hot isostatic press

• HIP 250 mm dia, 900 mm long is also available

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ODS MATERIALS
The powder is canned, extruded or Hipped
extruded
SAD confirmed the presence of Y2Ti2O7 along with
TiO2 and Y2O3
Upset can
Extruded rod
TEM Image of Fe-Ti-Y2O3
SEM Images of Fe-Ti-Y2O3 Forged
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ODS MATERIALS
Chararacterisation of Fe-Ti-Y2O3 Extruded Rod
Hardness 265 HV0.1 (Fe 150 HV) Density 98
Transverse direction
Micrographs of of Fe-Ti-Y2O3 HIPped and extruded
500X
Longitudinal direction
Longitudinal direction
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ODS MATERIALS
Present Status

• Atomised alloy powder (Fe-9Cr-0.1C-2W-0.2Ti) and
  yttria were milled in Simoloyer for 4 h

SEM images
As milled powder
Nano yttria powder
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ODS MATERIALS
The powder is degassed, canned and extruded
Hardness 500 HV0.2 Density 98
SEM image of extruded ODS alloy powder
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THANK YOU