CHARACTERISATION OF PM HSS WITH TAILORED HARDNESS OBTAINED BY TWO DIFFERENT PROCESSES

摘要

Fully dense T42 High Speed Steel (HSS) has been obtained by direct sintering. In order to use that material as a wear resistant structural component, its hardness has been selected to satisfy the service requirements without excessive wear of the components in contact with it. The same hardness has been reached by two different heat treatments. One consists of standard austenitising-quenching and multitempering. Austenitising temperature was selected low enough to obtain the targeted HRC without excessive overtempering of the martensitic matrix. The other heat treatment was isothermal annealing. From the austenitising temperature the specimens were cooled down to 600-650℃ maintained for 6-24 hours and then cooled down to R.T. giving a pearlitic matrix. The microstructure after heat-treatment and the thermal microestructural stability have been characterised for both materials. Results on strength and fracture toughness have also been reported.