20 - Metal injection molding (MIM) of high-speed tool steels

Abstract

Tool steels are inherently hard and difficult to machine, thus, net shape manufacturing by MIM is a viable option for manufacturing to promote cost savings. In this chapter an introduction into the MIM of these materials, focused on high-speed steels, is presented. A review of this class of steels is presented. This is followed by a discussion of the difficulties of processing these alloys by MIM. The difficulty is primarily associated with sintering – shape retention and carbon control. The shape retention is difficult in the high-speed tool steels because these alloys sinter by liquid phase sintering and the sintering window can be as small as 15°C in the case of M2 high-speed steel. Carbon control is a universal concern for all MIM processes, particularly if hydrogen-free atmospheres are used. Finally some example processing conditions and resulting microstructures are presented.