Abstract The M2 powder metallurgy high speed steel (PM HSS) was prepared with the carbonyl iron powders and carbide powders as raw materials. The powders were mixed via ball milling for 0-72 h, and then compacted by double-action pressing before sintered at 1 205 ℃ for 1h. The effect of the milling time on the carbon content, oxygen content, microstructure and mechanical properties of the M2 PM HSS were studied. The results show that with the increase of milling time, the particle size of the mixed powders decreases, the oxygen content increases significantly, and the carbon content of the M2 PM HSS decreases due to the carbon-thermal reduction. The main phases of M2 PM HSS are Fe, M6C, M2C and MC. With increasing milling time, metastable M2C carbide decreases, while M6C and MC carbides increase. Besides, with the increasing of milling time, the grain size of M2 PM HSS and particle size of carbide become finer, the carbide distribution is more uniform, and the relative density, hardness and bending strength of M2 PM HSS increase significantly. After milling for 72 h, the relative density of M2 PM HSS is 99.3%, and the hardness (HRC) and the bending strength are 50.6 and 2 852 MPa, respectively.
YANG Junhao,LIU Rutie,XIONG Xiang, et al. Effect of milling time on the microstructure and mechanical properties of M2 powder metallurgy high speed steel[J]. Materials Science and Engineering of Powder Metallurgy, 2020, 25(4): 296-303.
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2020, Vol. 25 
