What is powder metallurgy?

Powder metallurgy is the making of metal objects from powder, not molten metal casting or forging at softening temperatures. In some cases, the method of using powder is more economical, since when making small metal parts, such as gears for small machines, the casting will involve significant machining. In other cases, melting is impractical because of the very high melting point of the metal, such as tungsten, or because an alloy is required for mutually insoluble materials such as copper and graphite. Finally, powder metallurgy is used to produce a porous product that allows liquid or gas to seep through.