Fracture Toughness of Vacuum Sintered AISI M3:2 High Speed Steels

The aim of this investigation was to study and evaluate the fracture toughness (K_ICV) of an AISI M3:2 high speed steel that was prepared by powder metallurgical processing, which consisted of uniaxial cold compaction of irregularly shaped water atomized powders, without and with 0.3% of carbon in the form of graphite, followed by vacuum sintering to obtain compacts with densities close to its theoretical value. The sintered steels were then hardened by austenitizing, quenching and triple tempering. Chevron fracture toughness test samples were prepared from the compacts and the tests conducted to determine K_ICV. The microstructures of the specimens were examined by scanning electron microscopy (SEM), and the composition of the phases determined by x-ray diffraction analysis (XRD). The sizes of the primary carbides and of the austenite grains were determined using Quantikov digital analysis software. No significant difference in fracture toughness (K_ICV) between the two high speed steels AISI M3:2, austenitized at the different temperatures, was observed.

Keywords:
M3:2 High speed steel; powder metallurgy; K_ICV; characterization