Oil and gas pipelines are often used in harsh environments, and their welded joints are facing serious corrosion problems and great potential safety hazards. Laser-arc hybrid welding has become a promising welding method in the field of pipeline construction welding due to its high welding efficiency and small deformation. Hence, corrosion resistance of hybrid laser-MIG welded metal of X80 pipeline steel under different laser powers was investigated. Microstructure distribution in different zones in the welded joints was analyzed. Polarization curves, electrochemical impedance spectroscopy and SEM corrosion morphology of base metal and weld metal with different laser powers were also investigated. Influence of laser power on electrochemical corrosion properties was obtained. The results show that microstructures in hybrid laser-MIG welded metal are mainly composed of acicular ferrite, granular bainite and proeutectoid ferrite. Less granular bainite and more acicular ferrite/proeutectoid ferrite formed in the hybrid laser-MIG welded metal with increasing laser power. The polarization curves of both base metal and hybrid laser-MIG welded metal show no obvious passivation region. The base metal exhibits a higher corrosion current density and a lower charge transfer resistance compared with that of the hybrid laser-MIG welded metal. With increasing laser power, the corrosion resistance increases first and then decreases. The hybrid laser-MIG welded metal with a laser power of 3.0 kW shows the best corrosion resistance.
CHEN Yingchun， WANG Xinhua， WANG Cui， et al. Cathodic protection parameters of X65 and X80 pipeline steels in Dagang simulated soil solution［J］. Surface Technology， 2018， 47（06）： 218-223.
Wang Shuaixing， Yin Xiaole， Zhang Hao， et al. Coupling effects of pH and dissolved oxygen on the corrosion behavior and mechanism of X80 steel in acidic soil simulated solution［J］. Materials， 2019， 12（19）：3175.
CAO Rui， DING Yun， ZHAO Xiaokang， et al. Research Progress on Corrosion and Protection of Welded Joints of Pipeline Steels［J］. CORROSION SCIENCE AND PROTECTION TECHNOLOGY， 2017， 29（6）： 657-663.
Javidi M， Bekhrad S. Failure analysis of a wet gas pipeline due to localised CO2 corrosion［J］. Engineering Fai-lure Analysis， 2018， 89： 46-56.
Jafery K M， Embong Z， Othman N K， et al. Initial stage of corrosion formation for X70 pipeline external surface in acidic soil （peat） environmen［J］. Materials Today： Proceedings， 2022 ， 51： 1381-1387.
王晓香. 国内外超大输量天然气管道建设综述［J］. 焊管， 2019， 42（7）： 1-9.
WANG Xiaoxiang. Overview of the construction of super-large transportation capacity natural gas pipelines at home and abroad［J］. Welded Pipe and Tube， 2019， 42（7）： 1-9.
Ma Jing， Feng Fan， Yu Baiqing， et al. Effect of cooling temperature on the microstructure and corrosion behavior of X80 pipeline steel［J］. International Journal of Minerals， Metallurgy and Materials， 2020， 27（3）： 347-353.