Microstructures and corrosion properties of laser welded joint of 960 high-strength steel

The corrosion property of 960 high-strength steel joint by high power laser welding was studied. The microstructure of the welded joint was analyzed by scanning electron microscope(SEM) and optical electron microscopy. The corrosion behavior of the welded joint was investigated by potentiodynamic polarization. Stress corrosion sensitivity of the welded joint was investigated in simulated seawater at constant load. The results show that the corrosion process of 960 high strength steel starts with uniform corrosion, then the corrosion products drops off and the uniform corrosion forms at last. The electrochemical corrosion results show that the corrosion rate increases from weld, HAZ to base metal, and it decreases gradually with longer corrosion time. The fracture occurs at the heat affected zone due to the coarse grain of this zone in tensile test. Stress corrosion resulted in that the tensile strength of specimens decreased by 12%, and the fracture mode changed from ductile fracture to quasi-cleavage fracture.