Powder metallurgy is a process that reduces metals to powdered form and presses the powder into certain somewhat restricted shapes. A heating process called sintering is used to bind the metal powders and add strength to the finished product (see Sintering ).
Powder metallurgy has many advantages over other methods of making metal objects. Some metals will not mix (alloy) when heated to the fusion (melting) point. But these metals can be made to form valuable compounds by powdering them and then mixing the powders together. For example, graphite will not fuse with metals by heat alone. But it can be powdered and mixed with powdered metals, pressed into shape, and heated to make a bearing. Such a bearing does not need frequent oiling because the graphite acts as a self-lubricant. In addition, powder metallurgy is rapid, efficient, and accurate, and does not require skilled labor. Workers can also control the porosity (number, shape, and size of pores) in powder metallurgy.
Metals are made into powders in many ways. Molten metals can be atomized (broken down into tiny drops), and some solid metals can be crushed. Another method is electrolysis (see Electrolysis ). A fourth way is to heat the oxide compound of the metal in contact with hydrogen.
