Forging is the legacy process, starting with a billet of steel formed into a shape by applying pressure with either a hammer or press. Metals can be forged “cold” or “hot” with the process chosen based on complexity of the part, how close to finish size the part must be after forging and the number of parts being produced.
In contrast, powder metallurgy is a newer process, with mass production of PM products beginning in the mid- 20th century. Powdered metal starts with a fine metallic powder consisting of iron compounds and carbon. This powder is combined with other alloying agents such as copper or nickel and frequently a binding agent that helps hold it together after being pressed into a mold and then heated or sintered to fuse all the materials together. During sintering, the binding agent burns off, leaving just the alloying agents in a homogeneous condition in the form of the desired piece.
