The Effect Of Temperature On The Behavior Of Stress Corrosion Cracking Of 316L Stainless Steel In Wet H₂S Environment

Oil and gas equipments are suffering from serious corrosion problems during the exploitation and refining of petroleum,especially in high temperature and high pressure H₂S environment that widely exists in the oil and gas.So the corrosion problems are increasingly prominent so that it is a top priority topic to make a reasonable material selection in a special situation.316L austenitic stainless steel is provided with great corrosion resistance and controlled physical properties which is largely applied in the industrial system.Stress corrosion cracking（SCC）severely threaten austenitic stainless steel in acid Cl^-environment.Although a large number of predecessors made sufficient study on SCC of 316L austenitic stainless steel,some mechanism of SCC,especially in a handful of H₂S environment,is still ambiguous.Based on above condition,this project mainly explores the SCC behavior of 316L in H₂S environment in order to distinguish the mechanism of SCC on H₂S environment and discover improvement of 316L service in H₂S circumstance.First of all,Slow Strain Rate Testing（SSRT）were conducted here to study and compare SCC sensitivity of 316L in two environments（H₂S and acid Cl^-）.Results in the H₂S show that SCC sensitivity of 316L is obvious.It increases with increasing temperature until 200℃reaches its peak.However,the sensitivity decreases with continuously increasing temperature.There are two different types of fracture surface morphology here.When in the 200℃and 250℃the fracture is intergranular surface,the remaining temperatures are transgranular type.The SCC sensitivity in acid Cl^-environment is less clear than H₂S,so the role of hydrogen should not be overlooked in H₂S environment.Secondly,X-ray Diffraction（XRD）and Transmission Electron Microscopy（TEM）were conduct here to explore effect of hydrogen on microstructure and organization of316L.Results elucidate thatε-martensite and stacking fault and other organizations that are conductive to phase transformation are observed after hydrogen charging.This undoubtedly and greatly increase the hydrogen embrittlement susceptibility.At last,Transmission Electron Microscopy in situ stretching technology was conducted to explore effect of hydrogen on cracking propagation of 316L.Results demonstrate that hydrogen not only increases the tendency of martensitic transformation,but also reduces the size of deformed area in front of the crack tip.Hydrogen increases hydrogen embrittlement susceptibility in different ways.The above conclusions show that hydrogen plays an important role in the behavior of SCC in 316L in wet H₂S environment.