Use of high hydrostatic pressure for pressing parts from hard-metal powders

Hydrostatic pressing of unplasticized hard-metal mixtures in flexible shells enables compacts of the required shape and large longitudinal-to-transverse dimension ratio to be obtained without prepressing in a rigid die. Hydrostatically pressed compacts have fairly high strength and can be finish ground in the unsintered condition. As the sintering of hydrostatically pressed powders is characterized by a low value and small scatter of the coefficient of shrinkage, the dimensional accuracy of sintered parts can be increased. Hydrostatic pressing of hard-metal compacts without a plasticizer gives, after sintering, a virtually nonporous structure of low graphite content, which leads to increased strength. Compared with the hydrostatic re-pressing of conventionally pressed plasticized compacts, hydrostatic pressing substantially shortens the production cycle by eliminating the plasticizer addition, charge mixing, compact pressing, and plasticizer removal operations.