Steel Powders for the Powder Metallurgy (P/M) Forging Process 720181
The kind of powder selected for use in the P/M forging process depends on the requirements of the finished part. Most of the commercially available P/M powders can be used to make parts by P/M forging, and a majority of these applications do not require properties as high as those achieved by conventional forging. However, the most likely candidate for use in manufacturing parts that require the properties of conventional forgings is atomized low-alloy steel powder. When processed correctly, parts made from the atomized powders will duplicate the microstructure and hence the mechanical properties of conventional wrought steels.
Initial interest in alloys centered around the nickel-molybdenum steels (AISI 4600). However, because of economic factors there has been a shift to alloys leaner in nickel and to those that contain the less expensive elements such as manganese and chromium.
The properties of a P/M forged part are not only dependent on the quality of the powder used but also on the processes by which it is forged. Care must be taken in each of the three major P/M forging steps-powder manufacturing, preform processing, and powder forging-to insure that the part is not degraded by oxidation. Test results show that a low-alloy steel powder can be manufactured, processed using conventional P/M techniques, and hot forged to give properties that are equivalent to those of wrought material.