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Explain advantages and disadvantages powder Metallurgy.

Mumbai University > Mechanical Engineering > Sem 3 > Production Process 1

Marks: 5M

Year: May 2015

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The process of manufacturing of shaped components or semi-finished products such as bar and sheet from metal powder is called as Powder metallurgy. The technique of powder metallurgy combines unique technical features with cost effectiveness and generally used to produce sintered hard metals known as ‘carbides’ or ‘tungsten carbides’.

Advantages: .

Metal in powder form is costlier than in solid form. Further, expensive dies and equipment needed to adapt this process implies that the process is justified by the unusual properties obtained in the products. Powder metallurgy offers the following specific advantages.

  • Parts can be produced from high melting point refractory metals with respectively less difficulty and at less cost.
  • Production rates are high even for complex parts primarily because of the use of automated equipment in the process.
  • Near net shape components are produced. The dimensional tolerances on components are mostly such that no further machining is needed. Scrap is almost negligible.
  • Parts can be made from a great variety of compositions. It is therefore much easy to have parts of desired mechanical and physical properties like density, hardness toughness, stiffness, damping, and specific electrical or magnetic properties.
  • Parts can be produced with impregnation and infiltration of other materials to obtain special characteristics needed for specific applications.
  • Skilled machinists are not needed, so labour cost is low
  • Parts with controlled porosity can be produced
  • Bi-metallic products, sintered carbides and porous bearings can be produced only by this process.

Limitations:

  • High cost of metal powders compared to the cost of raw material used for casting or forging a component. A few powders are even difficult to store without some deterioration.
  • High cost of tooling and equipment. This is particularly a limitation when production volumes are small.
  • Large or complex shaped parts are difficult to produce by PM process.
  • Parts have lower ductility and strength than those produced by forging.
  • Uniformly high – density products are difficult to produce.
  • Some powders (such as aluminum, magnesium, titanium and zirconium) in a finally divided state present fire hazard and risk of explosion.
  • Low melting point metal powders (such as of zinc, tin, cadmium) give thermal difficulties during sintering operation, as most oxides of these metals cannot be reduced at temperatures below the melting point.
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