Effect Of Bending Deformation On Pitting Behavior Of 2205 Duplex Stainless Steel Under Wet-dry Cycling Condition

2205 duplex stainless steel?DSS 2205?is widely used due to its high strength,good plasticity and excellent corrosion resistance.However,various deformation modes such as bending,rolling,and stretching are usually involved in practical applications,.The material will corrode under these deformation conditions,causing serious damage.At the same time,whether the 2205 duplex stainless steel has pitting corrosion and its pitting corrosion in high temperature and high salt atmosphere is the key parameter for the wide application of this type of steel.In the laboratory electrochemical evaluation and analysis of the traditional reference electrode and three-electrode system,it is difficult to take into account the contradiction between pitting electrochemical process analysis and big data statistics.Therefore,the multi-droplet potential monitoring method is used to simulate the harsh environment of the ocean atmosphere,and the pitting behavior of DSS 2205 under various strain conditions is studied.The experimental temperature is 50?,The strain is controlled by U-bending machining.The cold rolling DSS2205 includes unstrained,6.3%tensile strain,7.1%compressive strain and sensitized samples;hot rolling DSS 2205 includes no strain,6.3%tensile strain,16.7%tensile strain,7.1%compressive strain and 25.0%compressive strain specimen.The main findings are as follows:?1?Statistical analysis of pitting and repassivation critical parameters of different states of DSS 2205 under MgCl₂ droplet dry-wet cycle.The results show that compared to the sample without strain,the cold rolling state of 6.3%tensile strain,7.1%compressive strain,sensitization treatment and hot rolling state of 6.3%tensile strain and 7.1%compressive strain all promoted the pitting process,inhibiting the repassivation process,and reducing the corrosion resistance of the sample;the hot rolling state of 16.7%tensile strain and 25.0%compressive strain have an inhibitory effect on the pitting process,the repassivation process is promoted,and the corrosion resistance of the sample is improved.?2?Observing and statistics on the pitting morphology of different states.The length and width of the pits of the hot rolling samples are generally smaller than those of the cold rolling sample;The morphology of pits in hot rolling samples showed a regular hemispherical shape under different strain conditions.The pits in the cold rolling state without strain,7.1%compressive strain and sensitized samples also showed a relatively regular hemisphere.However,the morphology of the pits in the cold rolling state of 6.3%tensile strain state is extremely irregular.After the study,it was found that the formation of such irregular morphology may be due to the difference in the degree of deformation of the two phases.The austenite phase of DSS 2205 preferentially corrodes under the action of 6.3%tensile strain.?3?The pitting behavior of MgCl₂ droplets and solution in cold rolling DSS 2205 under three conditions of no strain,6.3%tensile strain and 7.1%compressive strain was compared.The results show that the pitting potential obtained by the three state samples in the dry and wet cycle of the droplets is consistent with the trend of pitting potential measured by the potentiodynamic polarization curve in the solution.Among them,the 6.3%tensile strain has the most obvious reduction of pitting potential.7.1%compressive strain also reduces the corrosion resistance of cold rolling DSS 2205;6.3%tensile strain and 7.1%compressive strain state increase the probability of pitting corrosion,It also increases the range of pitting corrosion critical chloride ion concentration.