Microstructure and mechanical properties of M62 high-speed steel powder consolidated by high-temperature gas extrusion

Abstract

ABSTRACTSuper high-speed steel (AISI M62) powder was consolidated using high-temperature gas extrusion (HTGE). Consolidation of powder at 1200°C and 400 MPa pressure using HTGE resulted in 99.6% density while conventional extrusion (CE), at the same parameters resulted in 93% density. Variations in hardness with heat treatment were studied with respect to its microstructure, carbide size and distribution. The rods extruded using HTGE and CE and subsequently heat treated showed average matrix grain size of 1.6±0.5 µm and 6.0±2.0 µm along with homogeneous distribution of carbides of size 0.56 ± 0.31 μm and 1.52±0.68 μm, respectively. Such an ultrafine-grained microstructure obtained in HTGE resulted in a hardness of 950±20 HV (>68 HRC) in the quenched and tempered condition, which is the highest ever reported hardness value so far for this system, while CEed sample showed a hardness of only 756±18 HV (~62 HRC) under the same conditions.