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采用TEM、EDS、碳萃取复型等手段,研究了高速钢回火组织与性能演变规律,重点分析了过回火阶段合金碳化物演变与元素分配行为。结果表明,550℃回火后,高速钢组织中析出大量与基体共格的纳米级合金碳化物MC和M2C,硬度达到峰值。过回火阶段,M2C碳化物尺寸粗化倾向明显,并且发生结构转变,形成M23C6和M6C,而MC碳化物则表现出较高的尺寸和结构稳定性,对高速钢保持高温性能稳定发挥主要作用。随回火温度升高,碳化物中Fe含量明显下降、强碳化物形成元素含量上升,对碳化物析出和粗化行为产生重要影响。
The TEM and EDS, carbon extraction complex type and other means were used to study the microstructure evolution and properties evolution of high speed steel during tempering. The evolution and elemental distribution of carbides during over tempering were analyzed. The results show that after tempering at 550 ℃, a large amount of nanocrystalline alloy carbides MC and M2C are precipitated in the high-speed steel, and the hardness reaches the peak value. During the tempering stage, M2C carbides tend to have coarse coarsening tendency and undergo structural transformation to form M23C6 and M6C, whereas MC carbides exhibit higher dimensional and structural stability and play a major role in maintaining high temperature stability of HSS . With the increase of tempering temperature, the content of Fe in carbide decreases obviously and the content of carbide forming elements increases, which has an important influence on the precipitation and coarsening behavior of carbides.