Observation and Measurement of Sintered Parts Using Digital Microscopes

Advantages and Disadvantages of Sintering

Sintering is used to manufacture various parts because materials do not need to be melted.

Advantages of sintering

• Almost any material can be used as long as it can be powdered.
• Secondary processing is not required in many cases.
• Material losses are small.
• Complex shapes can be moulded.
• Materials can be freely mixed.
• Sintered parts are porous and thus light.
• Even materials with high melting points can be processed.

Disadvantages of sintering

• Powders are processed, which increases the material costs.
• Parts shrink when sintered.
• Mechanical properties, such as strength, are inferior to those produced by casting or pressing.

Principle of Sintering

Solid powder surfaces are unstable because atoms, molecules, and ions are not bonded. Joints called necks are formed when solid powders are heated. As atoms, molecules, and ions move (diffuse) from powder particle surfaces to necks, necks become larger and the surface areas decrease. As necks continue to grow through the initial, intermediate, and final stages, density increases and the sinter is completed.

Sintering Flow

1. Determine the mixing ratio of material powders and mix them with a mixier until the mixture becomes uniform.
2. Put the powder mixture into a metal mould and form it with a press.
3. Heat the moulded part in a sintering furnace for several hours.
   Material powders do not melt because the moulded part is baked to harden at temperature lower than their melting points. Material powders are firmly bonded to each other when heated for a long time and become a sinter.

Sintering furnaces are filled with gases to prevent sinters from becoming oxidised.
Sinters may be cut or polished to increase accuracy or heat-treated to increase hardness.