| Stainless steel is widely used in industries such as food,medical,and marine engineering due to its excellent corrosion resistance,excellent mechanical properties,and relatively low cost.Among them,the 304 and 316 series austenitic stainless steel still lacks resistance to chloride ion corrosion.Therefore,adding elements such as Mo and N to 316 stainless steel yields a super austenitic stainless steel that is resistant to chloride ion corrosion.This project uses 0Cr17Ni13Mo5 stainless steel as the material and regulates the microstructure of the stainless steel through rolling and annealing processes.Secondly,corrosion resistance tests such as potentiodynamic polarization curve,EIS test,and Mott schottky curve were conducted on austenitic stainless steel in different states in simulated seawater.The focus is on studying the changes in corrosion resistance caused by grain size,dislocation density,and precipitates,in order to reveal how the microstructure affects the passivation behavior of stainless steel and its impact on its corrosion resistance.Finally,austenitic stainless steel with good corrosion resistance is obtained.(1)0Cr17Ni13Mo5 austenitic stainless steel was rolled at room temperature with different deformation amounts(30%,50%,and 70%),and then annealed at different temperatures for 60 minutes.The microstructure of 0Cr17Ni13Mo5 austenitic stainless steel was studied as a function of cold rolling deformation and annealing temperature,and the phase composition and recrystallization of the stainless steel were analyzed.The research results indicate that during the cold rolling process of 0Cr17Ni13Mo5 austenitic stainless steel,the austenite grain boundaries gradually blur or even disappear with the increase of deformation.At the same time,the energy accumulated by deformation leads to the formation of a large number of shear bands,increasing the degree of deformation of grains,and increasing the number of structural defects.Some grains are broken.After cold rolling,0Cr17Ni13Mo5 austenitic stainless steel exhibits recrystallization behavior during annealing at 900 ℃,and after annealing at 1000 ℃,a grain characteristic with a significant difference in grain size is formed,exhibiting a distinct bimodal structure.(2)Conduct relevant corrosion performance tests on 0Cr17Ni13Mo5 austenitic stainless steel.Exploring the corrosion resistance of stainless steel from multiple aspects through potentiodynamic polarization curves,electrochemical impedance spectroscopy,electrostatic potential polarization curves,and immersion corrosion,and analyzing its patterns.The research results are as follows: Cr17Ni13Mo5 austenitic stainless steel has good corrosion resistance,can quickly passivate in chloride ion environments,and has a high passivation range(-0.2V-1.2V).The Nyquist plot of electrochemical impedance spectroscopy shows a large impedance radius,and has excellent resistance to pitting corrosion.Cold deformation can reduce the corrosion resistance of 0Cr17Ni13Mo5 austenitic stainless steel,but the sample with 70% deformation has a larger impedance radius and good passivation film stability.Annealing 70% of the cold-rolled samples at different temperatures showed that the annealed samples had a higher corrosion potential.The CR70-1000 sample has the highest impedance,the best passivation stability,and the best corrosion resistance.(3)The dislocation density between CR70-500 and CR70-700 samples is not significantly different,and the grain orientation transitions from<111>to<101>.Through comparison,it was found that dislocation density and crystal orientation have little effect on the corrosion resistance of the samples in this experiment.However,the CR70-1000 sample exhibits a clear bimodal structure and is distributed in two relatively concentrated forms to form galvanic corrosion and achieve good corrosion resistance.The precipitation phase uniformly distributed in the CR70-900 sample is abundant,which reduces the passivation ability of the metal matrix and causes serious corrosion around the precipitation phase.The precipitation phases in CR70-1000 samples are small and concentrated,which promotes metal passivation. |
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