T91/TP347H异种钢焊接接头高温时效组织对性能的影响

Effect of High Temperature Aging Microstructure of T91/TP347H Dissimilar Steel Welded Joints on Properties

异种钢焊接接头广泛应用于超超临界电站锅炉结构中。采用光学显微镜、扫描电子显微镜、显微硬度计、拉伸试验机等设备对服役10年并在750℃下进行不同时间时效处理的T91/TP347H异种钢焊接接头的组织与性能进行了分析。结果表明,随着时效时间的延长,焊缝组织基本稳定,T91和TP347H的热影响区晶粒尺寸逐渐增大,析出物逐渐聚集长大,发生粗化,TP347H热影响区析出物呈断续的链状分布,割裂基体,且TP347H热影响区组织老化程度更严重。时效处理450 h的TP347H热影响区内析出物主要有M7C3型、M23C6型和MX型。力学性能测试表明,随着时效时间的延长,焊接接头显微硬度逐渐降低,屈服强度和抗拉强度逐渐减小,断裂位置均在TP347H热影响区。

Dissimilar steel welded joints are widely used in ultra-supercritical power station boiler structure. The microstructure and properties of the T91/TP347 H dissimilar steel welded joints which have been in service for 10 years and aged at 750℃ for different time were analyzed by optical microscopy, scanning electron microscope, microhardness tester and tensile tester. The experimental results show, as aging time goes on, the microstructure of weld was generally unchanged, the grain size of T91 and TP347 H in the heat affected zone becomes gradually larger, precipitates gradually accumulate, grow,coarsen, the precipitates of heat affected zone of TP347 H presents a discontinuous chain distribution and split the matrix, and the aging microstructure of TP347 in heat affected zone is more serious. The precipitates in the TP347 H heat affected zone for450 h aging time mainly include M7 C3 type, M23 C6 type and MX type. The mechanical properties test results show that, with the aging time increasing, the microhardness of welded joints gradually decreases, the yield strength and tensile strength of welded joints gradually decrease. The fracture position of all the welded joints is located at the TP347 H heat affected zone.