M2高速钢大尺寸碳化物的形貌特征及析出机理

Morphology and precipitation mechanism of large carbides in M2 high speed steel

主要研究成品及锻造后M2高速钢碳化物种类和析出机理,为大尺寸碳化物控制提供理论依据。采用扫描电镜和能谱仪观测成品及锻造后M2高速钢中碳化物形貌、成分和分布;采用Thermo-Calc热力学软件计算M2高速钢的平衡析出相和Scheil凝固过程。结果表明,成品M2高速钢棒材中大尺寸碳化物网状分布包括MC、M6C、M2C碳化物及其复合碳化物;锻造后高速钢中出现带状碳化物和粗大碳化物堆积现象。平衡条件下,MC和M6C碳化物的析出温度分别为1 294和1 288℃,高于1 220℃奥氏体化温度;Scheil凝固时,MC、M6C和M2C碳化物依次析出。采用热处理及锻造难以消除M2高速钢中大尺寸碳化物,控制钢液凝固过程中碳化物的析出有重要意义。

The types and precipitation behavior of carbides in M2 high speed steel were studied.On the one hand,the scanning electron microscope was used to observe the morphology and distribution of carbides,and the chemical composition of these carbides was detected by energy dispersive spectroscopy.On the other hand,the Thermo-Calc was used to calculate the precipitation of carbides in equilibrium and Scheil model meanwhile.In the M2 HSS after annealing,the large carbides distributed along the network,which included MC,M_6C,M_2C carbides and mixture of them.After forging,the zonal distribution and accumulation of carbides arised in M2 HSS.MC and M_6C carbides precipitate at 1 294 and 1 288 ℃ respectively in equilibrium,higher than the austenitizing temperature.However,in Scheil solidification,MC,M_6C and M_2C carbide would precipitate in turn.It is difficult to eliminate large carbides in M2 HSS through heat treating and forging,but controlling the precipitation of carbides could be of great significance.