将两种Mo含量不同的Nb--Mo--V微合金钢在1200℃固溶0.5 h后淬火, 然后在450--650℃间不同温度回火4h, 研究Mo含量对其在回火过程中组织变化和碳化物形成的影响。结果表明：低Mo含量微合金钢样品的硬度峰值出现在550℃回火, 高Mo含量的出现在600℃回火；在650℃回火后, 高Mo含量样品中碳化物颗粒尺寸比低Mo含量的小。其原因是, Mo偏聚在碳化物外层抑制了Nb、V从铁素体基体扩散进入碳化物, 并降低了基体中C和合金元素向碳化物扩散的速率, 从而抑制了碳化物颗粒长大。
Nb–Mo–V micro–alloyed steels with different contents of Mo were tempered at 450–650℃ for 4 h after solution treatment at 1200℃ for 0.5 h, The Influences of Mo on the microstructureand the process of the carbides formation had been investigated by using three dimensional atom probe (3DAP) transmission electron microscopy (TEM). The results show that the hardness maximum of micro–alloyed steel with low Mo–contented appeared for tempering at 550℃, and that of high Mo–content sample appeared for tempering at 600℃; The carbides radius in high Mo–contented sample were smaller than that in low Mo–content sample tempering at 650 under TEM observation. That is due to Mo segregation at the carbides outer layer, inhibited the diffusion of the Nb and V from the matrix into the carbides, and also reduced the diffusion rate of C and alloyed element in matrix, so the growth of the particle was impeded.
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