【摘要】 研究了X80管线钢焊接接头组织对其超临界CO₂腐蚀行为的影响。采用金相显微镜观察高温回火后X80管线钢焊接接头的不同区域（基材区、细晶热影响区、粗晶热影响区和焊缝区）的组织特征。采用扫描电镜（SEM）观察该焊接接头不同区域在含饱和水的超临界CO₂（40℃,10 MPa）气相环境中腐蚀后的形貌，并采用X射线衍射仪（XRD）分析腐蚀产物物相。结果表明：基材区和焊缝区主要由多种形式铁素体构成；细晶热影响区和粗晶热影响区组织为多种形式铁素体和珠光体；在含饱和水的超临界CO₂环境中焊接接头各区域都发生明显的CO₂腐蚀，花型碳酸亚铁腐蚀产物岛分散在致密腐蚀产物表面，且腐蚀产物膜下出现腐蚀坑；基材区、焊缝区、粗晶热影响区的M-A岛主要在晶界析出，故膜下局部腐蚀严重，而细晶热影响区的M-A岛在晶体内弥散析出且晶粒细小，故膜下局部腐蚀轻微。更多还原

【Abstract】 The effect of microstructure of X80 pipeline steel welded joint on its corrosion behavior in supercritical carbon dioxide（SC-CO₂） environment was studied. The microstructure of base metal（BM）, fine grain heat affected zone（FGHAZ）, coarse grain heat affected zone（CGHAZ）, and welding metal（WM） of X80 pipeline steel welded joint after high temperature tempering were observed by metallurgical microscopy. The corrosion morphology of different zones in the welded joint corroded in gas phase environment of SC-CO₂ containing saturated water under condition of 40 ℃ and 10 MPa were observed by scanning electron microscopy（SEM）, and the phase composition of the corrosion scale was analyzed by X-ray diffraction（XRD）. The results show that the BM and WM consisted of different forms of ferrites. The microstructure of FGHAZ and CGHAZ were different forms of ferrites and pearlites. CO₂ corrosion could be found in all zones of the welded joint obviously in SC-CO₂ environment containing saturated water, and flowerlike iron carbonate corrosion scale islands dispersed on the surface of dense corrosion scale. Corrosion pits under the corrosion scale appeared at all zones. Localized corrosion under scale was heavy at BM, WM, CGHAZ due to Martensite-austenite（M-A） islands precipitating at grain boundaries, while it was slight at FGHAZ due to the dispersive precipitation of M-A islands in grain and grain refinement.更多还原