H13钢热疲劳后碳化物形态和组分的变化

采用薄膜电子衍射和萃取复型方法研究了压铸模具用钢H13钢经热疲劳后的碳化物形态和组分变化.结果表明,H13钢在热疲劳过程中表层硬度发生循环软化,循环软化主要与富铬的M23C6碳化物粒子的粗化和位错密度的降低有关.H13钢中富Cr的球状的M23C6碳化物在热疲劳过程中的成分变化是影响材料表层热疲劳循环软化的一个重要因素.球状的M23C6碳化物在热疲劳过程中,Cr和Mo等合金元素的含量在增加,而V的含量相对减少.

Changes of morphology and composition of carbides in H13 steel after thermal fatigue

The changes of morphology and composition of carbides in H13 steel used as casting die material were investigated by transmission electron microscopy after thermal fatigue. The results show that the surface layer of the H13 steel exhibits cyclic softening during thermal fatigue. The cyclic softening of surface layer is caused by the decrease of dislocation density in matrix and the coarsening of Cr-rich carbides, i.e. M23C6 carbide, during fatigue test. The changes of composition of M23C6 carbide play an important role to the cyclic softening of surface layer in H13 steel during thermal fatigue. Cr and Mo content of sphere-like M23C6 carbide is higher than that of square-like M23C6 carbide after thermal fatigue for 2000 cycles. In addition, the V content of sphere-like M23C6 carbide is lower than that in square-like carbide.