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Sintering1 2 4


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Sintering1 2 4

  1. 1. Powder Blending/Mixing Compacting Sintering Powder Metallurgy (P/M) Particulate Processing of Metals and Ceramics
  2. 2. Powder Metallurgy (P/M)  The Characterization of Engineering Powders  Production of Metallic Powders  Conventional Pressing and Sintering  Alternative Pressing and Sintering Techniques  Materials and Products for P/M
  3. 3. Powder Metallurgy (P/M) ? Metal processing technology in which parts are produced from metallic powders • Usual PM production sequence: Pressing - powders are compressed into desired shape to produce green compact • Accomplished in press using punch-and-die tooling designed for the part Sintering – green compacts are heated to bond the particles into a hard, rigid mass • Performed at temperatures below the melting point of the metal
  4. 4. Why Powder Metallurgy is Important ? • P/M parts can be mass produced to net shape or near net shape, eliminating or reducing the need for subsequent machining • P/M process wastes very little material - ~ 97% of starting powders are converted to product • P/M parts can be made with a specified level of porosity, to produce porous metal parts – Examples: filters, oil‑impregnated bearings and gears
  5. 5. Illustration
  6. 6. Incandescent bulbs
  7. 7. windshield penetrator sabot stabilizing fin propellant Kinetic Energy Penetrator materials Tungsten Heavy Alloy (WHA) Typical composition (wt.%): 90W-7Ni-3Fe Liquid Phase sintered 1500°C melting point of binder alloy (Ni-Fe) ~1465°C requirements • high density • dimensional precision Kinetic Energy Armour Piercing Penetrator
  8. 8. P/M for Automobiles
  9. 9. P/M Connecting Rods
  10. 10. Gears
  11. 11. Medical Radiation Shielding Tungsten Heavy Alloy
  12. 12. Cutting tool inserts Earlier, high speed steel (HSS) which was manufactured by casting route was used for cutting applications. Such steels a called cutting tool steels. However, they cannot be used by cutting at high speeds wherein the temperature can exceed 60 For still higher cutting output, hardmetals or cemented carbides [WC-(6-10 wt.%)Co] is used. Such alloys are consolidated liquid phase sintering.
  13. 13. P/M Work Materials • Mostly used for bulk ceramic components • Other P/M metals include copper, nickel, and refractory metals such as molybdenum and tungsten • Metallic carbides such as tungsten carbide are often included within the scope of powder metallurgy
  14. 14. Engineering Powders A powder can be defined as a finely divided particulate solid • Engineering powders include metals and ceramics • Geometric features of engineering powders: – Particle size and distribution – Particle shape and internal structure – Surface area
  15. 15. Milled Ti Powder
  16. 16. Electrolytic Cu Powder
  17. 17. Screen Mesh PS = 1 MC " tw
  18. 18. Particle Shapes in PM
  19. 19. Inter-particle Friction and Flow Characteristics Angle of Repose
  20. 20. Inter-particle Friction and Flow Characteristics
  21. 21. Production of Metallic Powders • In general, producers of metallic powders are not the same companies as those that make PM parts • Any metal can be made into powder form • Three principal methods by which metallic powders are commercially produced 1. Atomization 2. Chemical 3. Electrolytic • In addition, mechanical methods are occasionally used to reduce powder sizes
  22. 22. High velocity gas stream flows through expansion nozzle, siphoning molten metal from below and spraying it into container Gas Atomization Method
  23. 23. Iron Powders for P/M 50 µm