from powders to components depends on 2 key stages:
Compacting the powder into the required shape
Applying heat to promote the bonding of the particles (not necessary in
the case of certain ceramic materials)
Historically, the first group of materials to be formed from powders was
ceramics. The powder is mixed with water and then compressed into moulds.
The resultant shape has sufficient strength for it to be dried or placed
in a furnace for firing. This is the basis for the manufacture of most
pottery and earthenware today.
Most metals can also be formed in a similar way by compaction and a process
known as sintering. Metal particles are produced with diameters from 0.001
mm to 0.3 mm and then crushed at very high pressures into the desired
shape. The shape is then transferred into an oven and heated to 70-90%
of its melting temperature. The advantage of this process is the avoidance
of any waste material and, because of the tiny gaps between adjacent particles,
the ability to make the metal porous. It is important, however, to avoid
thin sections and sharp corners and it must be possible to withdraw the
shape from the mould in a straight line.
Typically gears and other mechanical parts are made by this process in
addition to filters and bearings which make use of the porosity of sintered