The effect of ultrasonic nanocrystal surface modification (UNSM) on the corrosion and stress corrosion cracking behavior of welded joint in district heating pipe were investigated. After UNSM treatment, the microstructure of welded joint was transformed from the grain boundary ferrite, widmanstätten ferrite to polygonal ferrite and grain refinement. In the electrochemical tests, the corrosion resistance of welded joint was increased after UNSM treatment. The grain refinement and microstructure change influence the oxide film stability, which cause the increase of corrosion resistance. The stress corrosion cracking behavior was measured by slow-strain rate tests with accelerated anodic and cathodic reactions. The results indicated that the UNSM treatment has a significant effect on the corrosion condition, whereas no effect appeared in the hydrogen embrittlement.

Subject
Water, Materials, Piping, Microstructure, Oxide formation, Oxide layers, Oxide films, Polarization curves, Welded joints, Corrosion resistance, Ferrite, Stress corrosion cracking, Ductility
Keywords:
weld, steel, corrosion, stress corrosion cracking, polarization
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2017
Association for Materials Protection and Performance (AMPP)
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