THE FABRICATION OF HIGH-SPEED TOOL STEEL BY ULTRAFINE POWDER METALLURGY

Abstract

Various powder-metallurgy techniques have been developed during recent years to avoid segregation effects associated with the conventional methods of casting and forming high-speed steels. These techniques have generally involved the consolidation of hot working or hot pressing of 50–500μm prealloyed powders into dense billets or rods.

The work described has demonstrated that much finer, 0·5–5μm, powders of M2 and M50 steels may be cold pressed and sintered to produce bodies with densities of 99% theoretical containing uniformly distributed 1–2μm particles of carbides. It is anticipated that the method will have application for the manufacture of complex-shaped parts with very small material losses and little machining.

An account is given of the preparation of the fine powders by ball-milling and their subsequent compaction, sintering, and microstructure. The control of carbon and oxygen levels by carbon addition to the powders is described.