Cross-scale Study On Local Failure Behavior Of Duplex Stainless Steel

2205 duplex stainless steel(DSS)consists of ferrite phase and austenite phase.It has excellent mechanical properties and corrosion resistance and is widely used in marine and petrochemical industries.Duplex stainless steel has excellent resistance to uniform corrosion,but it is prone to local corrosion such as pitting corrosion and stress corrosion cracking under certain circumstances.Pitting and stress corrosion cracking,due to their unpredictability,often leads to difficulties in estimating property damage.Therefore,it is of great practical and theoretical significance to study the local corrosion failure of duplex stainless steel.In this thesis,the effects of microstructure on the corrosion resistance of 2205 duplex steel were studied by macroelectrochemistry,scanning Kelvin probe,scanning vibration reference electrode and slow strain stress corrosion test(SSRT).The local corrosion resistance of duplex stainless steel after different solution treatment was studied by electrochemical workstation and scanning Kelvin probe.The results show that when the solid solution temperature is 950°C,the precipitation ofσphase leads to the decrease of local corrosion resistance of duplex stainless steel.When the solution temperature is between 1000°C and 1200°C,there is only two phases of ferrite and austenite in the duplex stainless steel,and the local corrosion resistance is not much different.Further studies on the results of scanning Kelvin probes have shown that local corrosion resistance is related to the partition coefficient of the two comparative examples and alloying elements in duplex stainless steel.The pitting corrosion resistance of duplex stainless steel was studied by electrochemical workstation and scanning vibration electrode.The results of cyclic voltammetry showed that the pitting corrosion of the solution treated at 1050°C was lower,while the other solution treated stainless steel withstand resistance The corrosion performance has decreased.The solution treated at 950°C was greatly affected by the Cl~-concentration,and the pitting potential decreased nearly linearly.The results of scanning the vibrating electrode show that at 950°C,the total potential of the anode reaction is the largest,and pitting is most likely to occur.The stress corrosion resistance of duplex stainless steel was studied by slow stress tensile analysis.The results show that the toughness loss of the solution treated at 950°C is large,and the toughness loss of the remaining samples in 3.5%NaCl solution is small.Further studies on cracks have shown that austenite has an inhibitory effect on crack propagation.The fast and slow polarization results indicate that there is no obvious stress corrosion sensitive range in the anode range.