High velocity compaction of high speed steel powder : possibilities and constraints

It is known that gas atomized powders as well as high alloyed metal powders are to press into green bodies using conventional quasi static pressing techniques. However, the development of the high velocity compaction (HVC) technique has expanded the possibility to compact a larger spectrum of metal Although the HVC technique has many similarities with conventional pressing techniques, the high energy impact makes it an interesting technique not only for the pressing of conventional metal powders to green bodies of high density but also for the pressing of difficult to press metal powders. Today, high speed steel (HSS) is increasingly being used in different types of components. Consequently, there is an increasing interest in the near net shape manufacturing of HSS components. The aim of the present study is to evaluate the possibility to utilize HVC to press green bodies from different types of HSS powder covering both gas and water atomized HSS The results show that the HSS powders investigated differ with respect to compaction properties, i.e. compressibility and green body quality. While the water atomized powders exhibit very good compaction properties, resulting in green bodies of high density, good surface finish and high strength, the gas atomized powders cannot be pressed in the as-atomized condition using HVC. However, agglomerated as well as milled gas atomized HSS powders show significant improved compaction properties compared to the as-atomized powders, although all showed defects of varying sizes depending on the applied energy during compaction.