The document discusses the powder metallurgy process which consists of three main steps: 1) blending and mixing of metal powders and additives, 2) compaction of the blended powder using pressure-based or pressureless techniques, and 3) sintering the compacted powder below the melting point to bond the particles together without melting. Optional secondary operations such as heat treatment, machining or infiltration can further process the sintered parts.

1. POWDER METALLURGY
PROCESS
Rona Mae L.Taduyo

2. 1.
• Blending and mixing (of powders)
2.
• Compaction
3.
• Sintering
Three Major Steps
* Optional and finishing secondary operations
Powder Metallurgy

3. Blending
– mixing powder of the same chemical composition but different sizes.
Mixing
– combining powders of different chemistries.
Blending and Mixing
Powder Metallurgy

4. Blending and mixing are accomplished by mechanical means:
Powder Metallurgy

5. Except for powders, some other ingredients are usually added:
Lubricants:
to reduce the particles-die friction
Binders:
to achieve enough strength before sintering
Deflocculants:
to improve the flow characteristics during feeding
Powder Metallurgy

6. Compaction
Pressure:
Cold Isostatic Pressing
Hot Isostatic Pressing
High Energy RateTechniques
Vibratory Compaction
Continuous Compaction
Forging or Extrusion
Pressureless:
Slip Casting
Gravity Compaction
Continuous Pressureless
Technique
Powder Metallurgy
Pressing process
Blended powders are pressed in dies under high pressure to form them
into the required shape. The work part after compaction is called a green
compactor simply a green, the word green meaning not yet fully processed.

7. COLD ISOSTATIC PRESSING
- Placement of powder in flexible rubber mold
- Hydrostatic pressurization in chamber by water
- Most common pressure of 400 MPa
Typical Application: Automotive cylinder liner
Compaction - Pressure
Powder Metallurgy

8. Cold Isostatic Pressing
Powder Metallurgy

9. HOT ISOSTATIC PRESSING
- powder container is usually made up of high melting point
sheet metal
Pressurizing media: inert gas
Common condition: 100 MPa, 1100°C
Advantages: Compacts of 100% density, good metallurgical
bonding, good mechanical properties
Limitations: wider dimensional tolerances, greater cost &
time
Powder Metallurgy

10. Hot Isostatic Pressing
Powder Metallurgy

11. HIGH ENERGY RATETECHNIQUES
- Explosive or spark discharge methods are applied in
closed die
- Short time & high pressures
-High punch & die wear, limited tolerances, high cost
VIBRATORY COMPACTION
- Simultaneous application of pressure & vibration
- Use of much lower pressures
- Complicated equipment design
Powder Metallurgy

12. CONTINUOUS COMPACTION
- Applied to simple shapes (rod, sheet, tube, plate etc)
- Flowing loose powder between a set of vertically oriented
rolls at much lower speed
Powder Metallurgy

13. Continuous Compaction
Powder Metallurgy

14. FORGING or EXTRUSION
• Canning of powder
• Heating or evacuation of sealed container followed by forging
or evacuation
• Mechanical or chemical removal of container material
Powder Metallurgy

15. Typical Compaction Pressure for
Various Applications
Powder Metallurgy

16. SLIP CASTING
- Preparation of slip (powder suspended in liquid and additives)
- Keeping slip in mold made up of fluid absorbing material
- Formation of slip casting
- Removal of slip followed by drying operation
Compaction - Pressureless
Powder Metallurgy

17. CONTINUOUS PRESSURELESS TECHNIQUE
- Application of powder in the form of slurry
- Consolidation and drying
- Used to produce porous sheets for electrodes of nickel-
cadmium batteries
Powder Metallurgy

18. Compressed metal powder is heated in a controlled-
atmosphere furnace to a temperature below its melting point,
but high enough to allow bounding of the particles.
Purpose - to increase strength & hardness of a green compact
Principal variables – temperature ( generally within 70 – 90% of
the melting point of metal or alloy), time (10 min. – 8 hours) &
furnace atmosphere
Sintering process is concerned with
– diffusion (surface of particles as temperature rises)
– densification (decreases porosity, increases particle contact
area)
– recrystallization & grain growth (between particles at the
contact area)
Sintering
Powder Metallurgy

19. The primary driving force for sintering is not the fusion of material, but formation
and growth of bonds between the particles, as illustrated in a series of sketches
showing on a microscopic scale the changes that occur during sintering of metallic
powders.
Powder Metallurgy

20. Powder Metallurgy

21. Powder Metallurgy

22. FINISHING / SECONDARY OPERATIONS
1. Sizing – cold pressing to improve dimensional accuracy
2. Coining or pressing - cold working process, to press details into
surface
- condensation of sintered product
3. Impregnation - impregnation with heated oil (self lubricated bearings)
- oil fills the pores of the part
4. Infiltration - placement of slug of a lower melting point metal against
the sintered part
- infiltration of molten metal by capillary action
- pores are filled with a molten metal
5. Heat treatment , Plating, Painting
Powder Metallurgy

23. Elemental or Alloy
metal powders
Additives
(lubricants or binders)
Blending and
Mixing
Compacting
Sintering
Optional Secondary
Finishing
Optional Secondary
Manufacturing
Finished Powder
Metallurgy Product
Powder Metallurgy

24. Finished Powder Metallurgy
Products Powder Metallurgy

25. Powder Metallurgy

26. Powder Metallurgy

27. THE END...