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The decomposition of the coarse primary M_2C carbide in M2 high speed steel was investigated by using optical microscope,scanning electron microscope,energy dispersive spectrometer and X-ray diffraction analysis.It is indicated that the SEM observation using deeply etched samples can clearly reveal the details of the decomposition products of primary M_2C eutectic carbides.The MC is granular and M_6C is peanut-shaped in the decomposition products,and the decomposition products are found to be very small in the size.With the increase of annealing temperature and duration,part of the peanut-shaped M_6C carbides change to simple skeleton-shaped ones.The phase transformation refinement of primary M_2C carbides in M2 steel by the decomposition of metastable M_2C carbides at high temperature can be obtained if suitable annealing parameters are applied.The complete decomposition of M_2C to M_6C and MC will occur when(1 100℃,4 h) or(1150℃,2 h) annealing treatment is employed in M2 high speed steel.
The decomposition of the coarse primary M 2 C carbide in M2 high speed steel was investigated by using optical microscope, scanning electron microscope, energy dispersive spectrometer and X-ray diffraction analysis. It is indicated that the SEM observation using deeply etched samples can clearly reveal the details of the decomposition products of primary M_2C eutectic carbides. MC is granular and M_6C is peanut-shaped in the decomposition products, and the decomposition products are found to be very small in the size .With the increase of annealing temperature and duration, part of of the peanut-shaped M_6C carbides change to simple skeleton-shaped ones. The phase transformation refinement of primary M_2C carbides in M2 steel by the decomposition of metastable M_2C carbides at high temperatures can be obtained if suitable annealing parameters are applied. The complete decomposition of M_2C to M_6C and MC will occur when (1 100 ℃, 4 h) or (1150 ℃, 2 h) ed steel.