Rare earth metal induced modification of γ -M 2 C,γ -M 6 C,and γ -MC eutectics in as cast M2 high speed steel

The effects of rare earth metals on the morphology of γ-M₂ C, γ-M₆ C, and γ-MC eutectics of as cast M2 high speed steel were investigated. The solidification of the specimens was monitored by conventional and differential thermal analysis and the characterisation of the microstructures was performed through optical and scanning electron microscopy. Rare earth metals favoured the formation of the M₆ C eutectic, at the expense of the M₂ C eutectic, and promoted the formation of the duplex M₂ C/MC and M₆ C/MC eutectics. The formation of these duplex eutectics was attributed to the decrease in the MC eutectic temperature.