关键词: 双相不锈钢, HAZ, 孔蚀, Cr_2N

Abstract: The effects of nickel content and Gleeble simulated heat affected zone(HAZ) of 2205 stainless steel on pitting corrosion were investigated in this paper. The results showed that nickel content, ranging from 4.5 wt% to 6.5 wt% in base metal, had only a minor effect on the electrochemical polarization curves, with all Enp's and Epp's falling in the rang of 1 1001200 mV. Comparing with the base metal, the simulated HAZ microstructure caused an increase in the anodic current density, a distinct decrease in both Enp and Epp , and a reduction in the passive range. Furthermore, hysteresis behavior was found as revealed in each cyclic polarization curve with different cooling cycle. It indicated that the pitting corrosion resistance and repassivation ability of duplex stainless steels were deteriorated by thermal cycling. Electrolytic extraction method proved that the Q values of integral cyclic polarization curves markedly increased while the nitrogen as Cr2N exceeded 20010-6. The susceptibility to pitting corrosion of HAZ was colsely related to the amount Cr2N precipitete. The higher the amount of Cr2N precipitated, the faster the rate of pitting propagation. However, in the nitride precipitate_free zones(PFZ), no pitting corrosion resistance was observed.

Key words: Duplex stainless steel, HAZ, Pitting, Cr2N