异质接头宏观偏析及其对持久性能的影响  

Macro⁃Segregation Structure in Dissimilar Metal Welds and Its Impact on Creep Resistance

作　　者：范曼杰 李松林 李克俭[2,3,4] FAN Manjie;LI Songlin;LI Kejian(Shanghai Electric Power Generation Equipment Co.,Ltd.Turbine Plant,Shanghai 200240,China;Department of Mechanical Engineering,Tsinghua University,Beijing 100084,China;Key Laboratory for Advanced Materials Processing Technology,Tsinghua University,Beijing 100084,China;State Key Laboratory of Tribology in Advanced Equipment,Tsinghua University,Beijing 100084,China)

机构地区：[1]上海电气电站设备有限公司汽轮机厂,上海200240 [2]清华大学机械工程系,北京100084 [3]清华大学先进成形制造教育部重点实验室,北京100084 [4]清华大学高端装备界面科学与技术全国重点实验室,北京100084

出　　处：《热力透平》2024年第4期276-283,共8页Thermal Turbine

基　　金：上海市科学技术委员会科技创新行动计划项目(20dzl205101)。

摘　　要：某异种金属焊接接头采用617镍基焊缝将617B镍基合金和10%Cr马氏体耐热钢焊接而成,对该接头开展了高温持久测试、失效机理分析和界面微观组织演化分析工作。高温持久测试的温度为600℃,应力测试水平为100、120、140 MPa。试验结果显示,断裂主要发生在镍基焊缝与10%Cr马氏体耐热钢界面处,并且随应力水平降低,界面处断裂的占比增加。进一步研究发现,发生于界面处的断裂主要与界面附近区域的宏观偏析带有关,宏观偏析带内的微观组织以高镍马氏体为主,其在高温持久条件下会发生局部奥氏体化,使得宏观偏析带与10%Cr马氏体耐热钢界面处形成多向拉应力状态,导致界面处形成蠕变孔洞,从而发生断裂。此外,还探究了宏观偏析带在焊接冷却过程中的固态相变过程,提出了奥氏体顺序析出的模型,成功地解释了焊缝同一柱晶根部的晶体取向可以“透过”宏观偏析带“传递”至另一侧柱晶的现象。研究成果可以为铁⁃镍基异种金属材料的焊接及蠕变性能评价提供参考。For dissimilar metal welded joint between 617B nickel⁃based alloy and 10%Cr martensitic heat⁃resistant steel filled with 617 nickel⁃based filler metal,analysis was carried on its high⁃temperature creep resistance,failure mechanism and interfacial microstructure evolution behavior.The high⁃temperature creep tests were conducted at 600℃with stress levels of 100,120 and 140 MPa.The test results showed that fractures mainly occurred at the interface between the nickel⁃based weld metal and the 10%Cr martensitic heat⁃resistant steel,and the proportion of fractures at the interface increased as the stress level decreased.Further research found that fractures at the interface were primarily related to the macro⁃segregation zone near the interface.The microstructure within the macro⁃segregation zone was mainly high⁃Ni martensite,which would undergo local austenization under high⁃temperature creep conditions,leading to a multi⁃directional tensile stress state at the interface between the macro⁃segregation zone and the 10%Cr martensitic heat⁃resistant steel.Thus,creep voids and fractures at this interface were formed.Additionally,exploration was carried out for the solid⁃state phase transformation process of the macro⁃segregation zone during the welding cooling process,and a model of sequential formation of austenite was proposed,by which the phenomenon could be explained that the crystal orientation of the columnar grain at the root could“transmit”through the macro⁃segregation zone to the columnar grain on the other side.The research findings can provide a reference for welding and creep performance evaluation of iron⁃nickel⁃based dissimilar metal welds.

关 键 词：异种金属焊接接头 高温持久 界面失效 宏观偏析 高镍马氏体 

分 类 号：TG407[金属学及工艺—焊接]