The term “powder metallurgy” covers the art of producing objects from metal powders, with or without the addition of non-metallic constituents. The powders may be pressed to a desired form in a suitable die and subsequently or simultaneously heated to produce a welded, alloyed, or coalesced mass. The material may then be suitable for immediate use or may be further worked by conventional methods, as, for example, by drawing down to fine wire. The chief advantages of this technique are that (1) it is possible to produce articles having unique properties unobtainable by other methods, e.g. controlled porosity; (2) it offers a method of producing parts in metals which cannot be melted commercially or only with considerable difficulty, and do not lend themselves to casting; (3) it is suitable for mixtures of metals and non-metals; (4) it can be used for metals which do not alloy; (5) it can be applied to metals of widely separated melting points or greatly different densities; (6) it offers a mass-production method of producing large quantities of parts identical in size and quality, perhaps of complex shape, without further operations; and is specially competitive where final machining constitutes a large proportion of the finishing costs by conventional methods. The limitations are: (1) restriction on the size of parts that can be produced on the presses available; (2) the restriction on the design of parts that lend themselves to pressing; (3) the fact that large quantities are required to justify the cost of dies and tools; (4) the cost of metal powders; and (5) the fact that the volume of the uncompressed powder is 2–3 times that of the finished piece. Future developments appear to lie in the direction of hot pressing, extended use of the process as the preferred technique for small parts in iron and other metals, and in combinations which retain desirable characteristics of the component metals, e.g. high wear resistance coupled with high electrical conductivity, which powder metallurgy makes possible in a way unobtainable by other means.