Analysis on black line defects in P91 steel welded joint aged at 650 ℃

doi:10.13251/j.issn.0254-6051.2020.01.049

Abstract

Abstract: P91 steel welded joints were aged at 650 ℃ for 210, 1000, 3000 and 5000 h, respectively. The variation of both the Cr, Mo distribution and the M ₂₃ C ₆ volume fraction were investigated along the welding “black line” defect and in the normal microstructure area by using SEM-EDS and MPST (multiphase separation technique). The results show that the microstructure of“black line” defect zone is composed of δ-ferrite and precipitated M ₂₃ C ₆, and some micro cavities and cracks can be found in the “black line”. Cr _eq is higher and promotes δ-ferrite formation in the “black line” zone. The depletion of Cr, the volume fraction and the coarsening of M ₂₃ C ₆ in the “black line” zone is severer than normal level with the increase of aging time.

Key words: P91 steel, welded joint, black line defect, M₂₃C₆ phase

CLC Number:

TG115

Sun Xiong, Liu Sheng, Wang Shutao, Yang Chao, Yang Qingxu, Li Xiqiang. Analysis on black line defects in P91 steel welded joint aged at 650 ℃[J]. HTM, 2020, 45(1): 254-258.

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