Sintering is the means whereby the powder particles are welded together and a strong finished part produced
The sintering of mechanical parts is usually done in a continuous belt furnace - in special cases a vacuum furnace is used.
In a simplified model there is:
• A single metal
• Spherical particles in contact
In the pressing operation the powder particles are brought together and deformed at the points of contact.
At elevated temperature - the sintering temperature - the atoms can move more easily and quickly migrate along the particle surfaces (the technical term is Diffusion).
Metals consist of crystallites.
At the sintering temperature new crystallites form at the points of contact so that the original interparticle boundaries disappear, or become recognisable merely as grain boundaries (This process is called Recrystallisation)
The total internal surface area of the pressed body is reduced by sintering.
Neck-like junctions are formed between adjacent particles as can be seen on the adjoining scanning electron micrograph of sintered filter material made from spherical bronze powder.
Figure 1. Scanning electron micrograph showing necking between adjacent metal particles.