Water-atomized Iron Powders for use in High Green Strength Powder Metallurgy Applications

摘要

Powder metallurgy is known to be a highly cost-effective manufacturing technique for the production of complex parts. Nevertheless, machining operations are often required once the parts are sintered in order to add features that cannot be readily compacted, such as side holes and undercuts. Such parts thus require expensive post-sintering machining operations, thus reducing the cost effectiveness of the powder metallurgy process. Green machining refers to a machining operation performed on parts that are yet to be sintered. Such machining operations are much cheaper to perform and for some features that need to be sculpted into the parts, green machining represents a highly attractive option. For machining to be possible on green parts, high mechanical coherence between the particles must be achieved, referred to as green strength. Conventional water-atomized steel powders typically have low green strength, in part due to their morphology that is somewhat rounded. Sponge iron, a specific type of powder obtained through oxide reduction, is the preferred powder type used to improve the green strength of powder premixes. Other types of powders can also provide high green strength at a lower cost than sponge iron powders. This study presents the results of the development of premixes, combining water-atomized, reduced iron powders and high performance lubricants designed for green machining applications. It is demonstrated that high green strength values are achievable using alternatives to sponge iron powders.