P91钢焊缝650 ℃时效黑线缺陷分析

将P91钢焊缝在650 ℃分别时效210、1000、3000和5000 h,采用扫描电镜-X射线能谱分析(SEM-EDS)和复相分离技术(MPST)研究了焊缝黑线/正常组织区域的合金元素(Cr、Mo)的分布变化以及M₂₃C₆体积分数变化。结果表明,焊缝黑线缺陷区域组织由δ-铁素体和周边析出相M₂₃C₆组成,黑线组织上有显微裂纹和显微孔洞;黑线组织区域的Cr_eq较大,促进了δ-铁素体的生成;随着时效时间的延长,黑线组织区域基体中贫Cr较正常区域严重,M₂₃C₆相所占体积分数更多,且颗粒更易粗化。

Analysis on black line defects in P91 steel welded joint aged at 650℃

P91 steel welded joints were aged at 650 ℃ for 210,1000,3000 and 5000 h,respectively. The variation of both the Cr,Mo distribution and the M23C6 volume fraction were investigated along the welding"black line"defect and in the normal microstructure area by using SEM-EDS and MPST( multiphase separation technique). The results show that the microstructure of"black line"defect zone is composed of δ-ferrite and precipitated M23C6,and some micro cavities and cracks can be found in the "black line". Creqis higher and promotes δ-ferrite formation in the"black line"zone. The depletion of Cr,the volume fraction and the coarsening of M23C6 in the "black line"zone is severer than normal level with the increase of aging time.