Influence of carbide content and morphology on machinability of hardened PM high speed steels

Powder metallurgical High-speed steels are increasingly important to meet the need for highest strength and abrasion resistance of tools for cold work applications. The manufacturing route determines tooling costs and surface properties with advantages when hard milling is applied. Anyhow, the influence of material properties on the cutting process isn't understood that well. The present work focuses on the influence of carbide content, type and morphology on the hard machining process. Material composition and heat treatment were chosen in order to isolate the influence of different carbide characteristics being caused by melt or PM (powder metallurgy)fabrication, material composition and heat treatment. The investigation encompasses HS 6-5-2 (PM and conventional) type materials as well as HS 14-3-5-11 PM in different heat treatment states. The presented results expand the known process models by attributing the chip forming mechanisms and its implications (cutting forces, chip formation, microstructure) to the relevant material characteristics.