M42高速钢电渣重熔及锻造退火后碳化物的析出

Precipitation behaviors of carbides in M42 high speed steel during ESR and forging

通过X射线衍射分析、光学显微镜和透射式电子显微镜观察以及相关热力学计算,对比研究了M42高速钢电渣锭及锻后退火两种状态所析出碳化物的类型、尺寸、分布及析出条件。得出M42高速钢电渣锭中的碳化物主要为Mo_2C亚稳态碳化物和少量Cr_7C_3碳化物,Mo_2C碳化物尺寸较大,主要呈层片状、纤维状和棒状沿晶界析出。锻造退火后的M42高速钢中碳化物类型主要为Cr_7C_3,VC和Fe_2Mo_4C,平均尺寸小于10μm且分布均匀,形态以方形、不规则球形和小颗粒为主。M42高速钢电渣锭中的Mo_2C在锻造过程中可以分解为Fe_2Mo_4C和VC。根据冶金热力学计算得出,Mo_2C和VC在固液两相区析出,析出温度分别为1 229和1 222℃;Cr_7C_3在固相中析出,析出温度为842℃。

The characteristics （type, size, distribution and precipitation conditions） of precipitates in M42 high speed steel under electroslag remelting （ESR） and forging were analyzed by X-ray diffraction （XRD）, optical microscopy （OM）, transmission electron microscopy （TEM）, and thermodynamic calculation. The precipitates in the steel after ESR were mainly plate-shaped, fibrous and rod-like Mo2C metastable phase precipitating along the grain boundaryat a large sizeand Cr7C3 carbide. The precipitates in the steel after forging were mainly Cr7C3, VC and Fe2Mo4C, whoseaverage size wasless than 10gm. The precipitates existed as the shape of square, sphere and small particle.The Mo2C carbides in M42 high speed steeldecomposed into a mixture of Fe2Mo,C and VC during forging process. Thermodynamic calcula- tion results reveal that Mo2C and VC precipitate in the solid-liquid zone at 1 229 and 1222℃, respectively. Cr7C3 precip- itates in the solid zone at 842℃.