激光冲击处理对X70管线钢焊接接头应力腐蚀的影响

Effects of laser shock processing on stress corrosion of X70 pipeline steel welded joints

利用激光冲击波对X70管线钢焊接接头进行了表面改性处理,通过SSRT分析了激光冲击处理对试样在NACE饱和H2S溶液中应力腐蚀的影响。采用扫描电镜观察了激光冲击处理前后试样表面腐蚀产物形貌、断口形貌和应力腐蚀裂纹形貌等,并用能谱分析仪分析了腐蚀产物化学成分组成,探讨了激光冲击处理对试样SCC的影响机理。结果表明:激光冲击处理后焊接接头抗拉强度、伸长率和断面收缩率分别提高了5.1%、4.5%和28.7%,内积功的SCC敏感性指数Iscc从50.94%下降至45.10%,降低了11.64%,断口形式由脆性断裂转变为韧性断裂。激光冲击处理改善了焊接接头表面应力状态和材料组织结构,减缓了裂纹的萌生和扩展,增强了其抗SCC的性能,但不能消除明显的应力腐蚀倾向;激光冲击处理降低了氢致开裂的倾向,有利于提高焊接接头抗H2S应力腐蚀的性能。

Surface of X70 pipeline steel welded joint was processed by laser shock wave,and SSRT( slow strain rate test) was used to investigate the effects of LSP( laser shock processing) on stress corrosion of the welded joint samples in NACE solution with saturated H2 S. The morphology of surface corrosion,fracture surface and stress corrosion cracks of the samples before and after LSP was observed by SEM,and chemical components of corrosion products were analyzed with EDS,and the mechanism of LSP on SCC was discussed. The results show that the tensile strength,the elongation and the reduction of area of the welded joint after LSP increase by 5. 1%,4. 5% and28. 7%,respectively,while the SCC sensibility index Isccof inner product powers after LSP decreases from 50. 94% to 45. 10%,and the fracture mode changes from brittle fracture to ductile fracture. The surface stress state and micro structure of the welded joint are improved after LSP,the crack initiation and propagation are slowed down,and the performance of SCC resistance is enhanced,but LSP can not eliminate the obvious tendency of stress corrosion. The tendency of HIC( hydrogen induced corrosion) is reduced by LSP,which is beneficial to improving the H2 S stress corrosion resistance of the welded joint.