Ferrous P/M

Specifying powder-metallurgy (P/M) parts and their consolidation process used to be a simple process: Design the part, select the metal powders and lubricants that provide the required properties, compact the powders into a briquette, and sinter the briquette into its finished form. Through this procedure, millions of parts have been produced for applications ranging from automobiles to appliances and from business to farm and garden machines. However, the needs of industries have changed significantly. Removing weight from all products has risen to primary importance. Energy, tooling, and materials costs now figure prominently in parts design, and productivity has emerged as the watchword of the eighties. With these changes have come changes in powder-metallurgy technology. Through the many manufacturing processes, improvements have been made in the powders themselves -- improvements such as lower levels of inclusions and higher compressibility. In addition to conventional iron and steel metals, the list of available powders has been expanded to include new classes of tool steel, as well as materials such as cermets and alloys of titanium, nickel, and aluminum. Accompanying these developments has been the growth of new consolidation technologies. As a result, design engineers need current information on which P/M technologies are viable, cost effective, and production effective, and which have potentially wide application. Although powder metallurgy is used to fabricate parts from just about any metal, the most commonly used metals are the iron-based alloys. Low-density iron P/M parts (5.6 to 6.0 gm/cm≥), with a typical tensile strength of 16,000 psi, are usually used in bearing applications. Copper is commonly added to improve both strength and bearing properties. Alloy-steel powders are sometimes hot forged to high or nearly theoretical density to form parts with improved mechanical properties which, when heat treated, may have tensile strengths to 170,000 psi. Powder forging (P/F) is now