A study of the debinding and sintering behavior of T42 high-speed steel produced by powder injection molding (PIM)

Abstract

Tool steels have a large range of applications including hot and cold working of metals and injection molding of plastic or light alloys. High-speed steel (HSS) is specifically used for cutting tools and for components subjected to extreme wear conditions, because of its high strength, wear resistance, hardness, toughness, and fatigue resistance. The microstructure of HSS can be described as a metallic matrix iron composite containing a dispersion of hard and wear-resistant carbides. Specimens were manufactured experimentally from T42 powder (50-80 vol%) and mixed binder (20-50 vol%) by powder injection molding. The binders (green parts) were debound in n-hexane solution at 60 A degrees C for 8 h and thermally debound in a mixed N-2-H-2 gas atmosphere for 8 h. Specimens were sintered under high vacuum (10(-5) Torr) at different temperatures. When sintering was performed at 1,260 A degrees C, the specimen sintered under high vacuum had the highest hardness (550 Hv). The carbides were smaller (1 mu m) and well distributed. Grain size was 10 mu m. When sintering was performed under high vacuum at temperatures above 1,280 A degrees C the carbides changed to eutectic carbide located at grain boundaries. Grain growth was observed. Specimens sintered at other pressures had lower density and hardness than those sintered under high vacuum.