Abstract:The pure nickel N6 plasma arc weld was subject to U-shaped bending deformation heat treatment.The grain boundary characteristic distribution (GBCD) of Non GBE and GBE samples and its influence on corrosion behavior were studied by grain boundary character distribution (EBSD) and orientation image microscopy (OIM). The results show that the proportion of lowΣCSL grain boundaries increase to more than 54.1% by the TMP after U-shaped bending deformation and subsequent annealing at 900℃ for 10 min, and simultaneously the large-size highly-twinned grain-cluster microstructure is formed.The recrystallization nucleation point increased and the grain size decreased to 146 um during annealing.The corrosion resistance of GBE sample is higher than that of Non GBE sample. The self corrosion current density of GBE sample is less than that of Non GBE sample, and the capacitive arc radius, impedance modulus and phase angle of GBE sample are greater than those of corresponding Non GBE samples.Pitting corrosion occurr on the surface of samples.The passivation film on the surface of the coating is destroyed by C1-in the solution and forms pitting pits at the initial stage.With the prolongation of immersion time, the concentration of Ni2+near the anode metal reaches saturation or supersaturation. the bound water in the corrosion product film reacts with Ni2+ forms Ni(OH)2, and then the Ni(OH)2 are dehydrated and decomposed into NiO.Corrosion products cover the surface of the sample and form a corrosion product film, which are composed of NiO and Ni(OH)2. The corrosion product film has a protective effect,which prevents Cl- from penetrating through the corrosion products to the sample surface and the pitting is controlled.