Abstract
Hot work tool steel (AISI H13) and high speed steel (AISI M3:2) powders were successfully co-sintered to produce hybrid tool steels that have properties and microstructures that can be modulated for specific applications. To promote co-sintering, which is made difficult by the various densification kinetics of the two steels, the particle sizes and structures were refined by mechanical milling (MM). Near full density samples (>99.5%) showing very fine and homogeneous microstructure were obtained using spark plasma sintering (SPS). The density of the blends (20, 40, 60, 80 wt % H13) was in agreement with the linear rule of mixtures. Their hardness showed a positive deviation, which could be ascribed to the strengthening effect of the secondary particles altering the stress distribution during indentation. A toughening of the M3:2-rich blends could be explained in view of the crack deviation and crack arrest exerted by the H13 particles.
Highlights
Materials for tooling applications, such as tool steels, require a proper compromise between hardness and toughness to provide high wear resistance combined with adequate resistance to cracking.An increased wear resistance often comes at the expense of other properties, such as impact and fracture toughness
Hybrid tool steels were successfully produced by mechanical milling and spark plasma sintering of AISI H13 and AISI M3:2 powders
mechanical milling (MM) markedly reduced the particle size, which minimized the negative influence of the different densification kinetics of the two steels
Summary
Materials for tooling applications, such as tool steels, require a proper compromise between hardness and toughness to provide high wear resistance combined with adequate resistance to cracking. Materials 2016, 9, 482 hindered by the already sintered HWTS skeleton, resulting in the formation of large pores and a considerable decrease in the hardness and toughness In this respect, a beneficial effect has been demonstrated through the use of small diameter particles, which minimize the interaction between the two components, and the blends achieve nearly full density and good properties [8,12,13]. HWTS and HSS powders were mechanically milled to refine their particle size and microstructure These MM powders were blended to produce fully dense hybrid steels with different compositions. The density, hardness, toughness and microstructure were investigated and compared to those of unmilled blends [8]
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