淬火保温时间对FB2耐热钢组织与性能的影响

Effect of quenching holding time on microstructure and properties of FB2 heat-resistant steel

利用光学显微镜(OM)、扫描电镜(SEM)和透射电镜(TEM)对不同淬火保温时间下淬火及回火后的FB2马氏体耐热钢进行显微组织观察,并通过室温拉伸和冲击试验对不同淬火保温时间下热处理后FB2钢的强度、塑性、冲击吸收能量及硬度进行了测试。结果表明,在1100℃淬火,保温时间为1~8 h时,FB2钢的强度、塑性及硬度变化不大,冲击吸收能量随着保温时间的延长而降低。淬火保温时间为8~16 h时,随着保温时间的延长,FB2钢的强度和塑性变化不大,硬度下降,冲击吸收能量上升。随着淬火保温时间在1~8 h范围内增加,FB2钢的原奥氏体晶粒尺寸不断增加,未溶碳化物数量减少,合金元素扩散不均匀,回火后的晶界碳化物粗化程度增加,而当保温时间延长为16 h时仍有碳化物未固溶,晶界及晶内各级界面上碳化物尺寸没有明显差异。

Microstructure of FB2 martensitic heat-resistant steel after quenching and tempering under different quenching holding time were observed by means of optical microscope(OM),scanning electron microscope(SEM)and transmission electron microscope(TEM).The tensile properties,impact absorbed energy and hardness of the heat treated FB2 steel were tested at room temperature.The results show that when quenching at 1100℃,the strength,plasticity and hardness of the FB2 steel after quenching and tempering have no apparently change with the quenching holding time increasing from 1 h to 8 h,while the impact absorbed energy decreases.When the quenching holding time is increasing from 8 h to 16 h,the strength and plasticity change little,the hardness decreases and the impact absorbed energy increases.With the increase of quenching holding time in the range of 1-8 h,the prior austenite grain size of the FB2 steel is increased,and the number of undissolved carbides is decreased,meanwhile,the alloying elements diffuse unevenly and the grain boundary carbide coarsening increases after tempering.However,there are still carbides undissolved when the quenching holding time is extended to 16 h,and no significant difference in the carbide sizes at grain boundaries and the intragranular boundaries.