高温短时时效对TP347HFG钢组织和力学性能的影响

Effects of High Temperature Short-term Aging on Microstructure and Mechanical Properties of TP347HFG Steel

为探究高温短时时效处理后TP347HFG钢组织、性能的变化特点,采用金相显微镜、扫描电镜观察、布氏硬度测试、拉伸测试等试验手段研究了720℃下48、72、96和120 h时效处理后的试样。结果表明,和未时效的相比,时效后材料强度和硬度有明显的提高,变化趋势是随时效时间增加先增加后降低,在72 h时达到最大值。72 h时效处理后,原始粗大的未溶解第二相消失,基体中弥散析出的细小第二相(主要是NbC)逐渐增多,晶界也有少量第二相(主要是Cr23C6)析出,晶粒大小变化不明显,平均尺寸维持在30μm左右;时效96 h后晶界处第二相数量增多,开始聚集、熔合、粗化,有一部分晶粒异常长大,至时效120 h时晶界处可见大量粗大的第二相,晶粒的平均尺寸约为35~40μm。说明时效处理后TP347HFG的性能的改变与时效后组织的变化(第二相的析出、晶粒的长大)有关。

In order to investigate the change of microstructure and properties of TP347HFG steel after high temperature and short time aging treatment,the metallographic microscope and scanning electron microscope obser vation,Brinell hardness test and tensile test were used to study the aging samples treatment at 720℃for 48 h,72 h,96 h and 120 h.The results show that,compare with the unaged materials,the strength and hardness of the materials increase obviously after aging,and the change trend is first increases and then decreases with the increase of aging time,and it reaches the maximum value at72 h.After aging treatment for 72 h,the coarse undissolved second phase disappears,and the fine second phase(mainly Nb C)in the matrix gradually increases.A small amount of second phase(mainly Cr23C6)is precipitated at grain boundary,and the grain size does not change obviously,the average size is about 30μm.After 96 h aging,the number of the second phase at grain boundary increases,and the second phase begins to gather,fuse and coarsen.Some of the grains grow abnormally.After aging for 120 h,a large number of coarse second phases are observed at the grain boundary,and the average grain size is about 35-40μm.It shows that the change of the properties of TP347HFG after aging treatment is related to the change of microstructure(precipitation of the second phase,grain growth)after aging.