LI Kejian, LI Xiaogang, ZHANG Yu, et al. Microstructure evolution and high temperature failure mechanism of dissimilar metal welded joints[J]. 2020,50(9):17-43. DOI： 10.7512/j.issn.1001-2303.2020.09.03.
使用镍基焊缝连接铁素体基耐热钢和奥氏体不锈钢(或镍基合金)形成的异种金属焊接接头(DMWs, Dissimilar Metal Welds)在核电、火电、石化等行业有着广泛的应用。DMWs在高温低应力服役条件下经常会出现早期失效,导致机组非正常停机,带来巨大的经济损失和安全隐患,故DMWs的早期失效问题一直受到工程界和学术界的重点关注。围绕DMWs的早期失效问题,回顾并总结了近几十年来该领域的相关研究成果。首先,介绍了DMWs的组织特点,重点关注了铁素体基耐热钢与焊缝界面附近区域的冶金特点,包括界面马氏体层、碳迁移、Ⅰ/Ⅱ型碳化物等;其次,简要总结了DMWs焊接残余应力的特点及其影响因素;再次,汇总了DMWs的高温蠕变数据,针对DMWs蠕变断裂位置转移的特点进行了分析,其中沿铁素体基耐热钢与焊缝界面断裂是DMWs失效的显著特征,这种失效方式与界面处应变集中、热应力、基体组织退化、碳化物粗化以及氧化等有关;最后,给出了若干种延长DMWs服役寿命的方法和建议。
Dissimilar metal welds（DMWs） formed by joining ferrite based heat-resistant steel and austenitic stainless steel（or nickel base alloy） with nickel base weld are widely used in nuclear power, thermal power, petrochemical and other industries. The early failure of DMWs often occurs under the condition of high temperature and low stress, which leads to the abnormal shutdown of the unit and brings huge economic losses and safety risks. Therefore, the early failure of DMWs has been focused by the engineering and academic circles. In this paper, the early failure of DMWs is reviewed and summarized. Firstly, the microstructure characteristics of DMWs are introduced, and the metallurgical characteristics of the region near the interface between ferrite based heat-resistant steel and weld are focused on, including martensite layer, carbon migration and type I/II carbides. Secondly, the characteristics of welding residual stress and its influencing factors are briefly summarized. Thirdly, the high temperature creep data of DMWs are summarized, aiming at the characteristics of creep fracture location transfer of DMWs, the fracture along the interface between ferrite based heat-resistant steel and weld is a significant feature of DMWs failure. This failure mode is related to strain concentration, thermal stress, matrix structure degradation, carbide coarsening and oxidation. Finally, some methods and suggestions for prolonging the service life of DMWs are given.
dissimilar metal welded jointheat resistant steelnickel base alloyaustenitic stainless steelmicrostructurecreepearly failure