What is Sintering? Applications, Advantages and Disadvantages of Sintering

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What is sintering?

Sintering is a thermal treatment technique of compacting and forming of solid material using heat and pressure without melting the main constituent (or without heating it to its liquefaction temperature). It is basically atomic diffusion. It will happen in any material at any temperature above absolute zero, but it is faster in higher temperature. When the heat is applied to powder compact, the average grain size increases, reducing the porosity and the compact gets densified. This basic phenomenon is known as sintering.

The sintering consumes surface energy for creating bonds between solid particles. In thermodynamic understating, it is a surface energy reduction process by reducing surface area. Since small particles have more surface energy, the sintering is faster in small particles than in large particles.

Sintering is mainly classified into solid-state sintering and liquid phase sintering. When powder compact is densified wholly in the solid state at the sintering temperature, then it is known as solid sintering. In liquid phase sintering, the liquid phase is present in the compact (or particles melting occurs) during sintering. When compared to solid-state sintering, the liquid phase sintering allows easy control over the microstructure of grains, and hence processing cost is low. Liquid phase also enhances mass transport. Some other types of sintering are transient liquid phase sintering and viscous flow sintering.

Example of pressure-driven sintering: forming of a single ice piece when pressing two ice cubes together. Formation of the glacier from snowfall.
Example of temperature-driven sintering: ice cubes in water adhere to each other, which is driven by temperature difference.

Sintering Applications, Advantages and Disadvantages

Sintering is used to make strong, reliable and high-performance shapes, such as ceramic, medical implants etc. Sintering happens when atoms of material at boundaries of particles diffuse and form one single solid particle. It is helpful to reduce or eliminate porosity, increase conductivity, etc.

Advantages
  • Making of complex shapes directly, without secondary machining operations
  • Used for the shaping of materials which have a very high melting point.
  • Reduce the porosity.
  • Increase conductivity.
  • Preservation of purity.

Disadvantages
  • Large material quantity required.
  • High initial capital cost
  • Size is limited based on the size of the chamber sintering machine.
  • Since it needs high temperature, the process leads to high energy cost.


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