P91和P92马氏体耐热钢焊缝中的黑线

Black lines in welds of P91 and P92 martensitic heat resistant steels

借助光学显微镜、扫描电镜、能谱仪、聚焦离子束和透射电镜等设备,研究了P91和P92马氏体耐热钢埋弧焊焊缝中黑线的分布特点、结构特征和形成原因。结果表明:黑线长短不一,主要位于焊缝的柱状晶之间,由线状排列的面心立方M_(23)C_(6)碳化物组成,形成原因是焊接过程中Cr和Mo等元素在柱状晶间偏聚,焊后热处理时M_(23)C_(6)碳化物在柱状晶晶界析出,腐蚀后在光学显微镜下呈黑色线状。

By means of optical microscope, scanning electron microscope, energy spectrometer, focused ion beam and transmission electron microscope, the distribution characteristics, stuctural characteristics and formation reason of black lines in submerged arc welding welds of P91 and P92 martensitic heat resistant steels were studied. The results show that the black lines were different in length, mainly located between the columnar crystals of the weld, and were composed of M_(23)C_(6)type carbides with a linear arrangement of face centered cubic. The reason for their formation was that Cr and Mo elements segregated between the columnar crystals during welding, M_(23)C_(6)carbides precipitated on the columnar crystal bondary during post weld heat treatment, and appearred as black lines under the optical microscope after corrosion.