Service Performance Of Co_1.5CrFeNi_1.5Ti_0.5Mo_0.1 Alloy In Sour Oil And Gas Field Environment

"High depth,high temperature,high acid"and other harsh conditions of oil and gas exploration and development has become the current situation of China's oil and gas industry.So the research and application of new corrosion resistant alloy is still the focus of domestic and foreign oil and gas industry.At present,the research on the corrosion resistance of the new material-high entropy alloy mainly focuses on the influence of preparation method,alloy elements and solidification rate,and less on the behavior research in some specific application environments,Moreover,there is no research report on the corrosion of high entropy alloy by H₂S or CO₂.Based on a large number of domestic and foreign literature research on the corrosion performance of high entropy alloy,firstly,Co_1.5CrFeNi_1.5Ti_0.5Mo_0.1 high entropy alloy prepared by vacuum arc melting is used to characterize the microstructure and phase structure of as cast high entropy alloy by means of SEM,EBSD,TEM,etc The microstructure and phase structure are typical coarse grain structure and simple face centered cubic?FCC?structure.Secondly,the pitting corrosion resistance of as cast high entropy alloy was studied by FeCl₃ solution accelerated experiment.With the help of laser confocal microscope,the three-dimensional morphology of pitting pits was observed to determine the pitting resistance.The corrosion rate of high entropy alloy in simulated environment was calculated by weight loss method.SEM,BSE,XRD,XPS and EDS were used to observe the morphology and local corrosion characteristics of corrosion products.The results show that the high entropy alloy has strong pitting resistance,and the average corrosion rate increases with the increase of temperature under different temperature conditions.The composition of the corrosion product film is Cr?OH?₃,Cr₂O₃,COO and Co₃O₄ by XPS analysis,NiO,TiO₂,FeS₂,FeS;the average corrosion rate under different partial pressure conditions generally has little difference.With the decrease of H₂S partial pressure,the corrosion rate shows an upward trend,and the corrosion rate is the largest under CO₂ environment.The composition of the corrosion product film on the surface of the high entropy alloy is Cr?OH?₃,Cr₂O₃,COO,Co₃O₄,NiO,TiO₂,FeS₂,FeS,Fe₂O₃ under the condition of H₂S.For single CO₂ environment,the composition of corrosion products on the surface of high entropy alloy is Cr?OH?₃,Cr₂O₃,COO,Co₃O₄,NiO,TiO₂,FeCO₃and Fe₂O₃.Finally,the passivation behavior of as cast high entropy alloy in H₂S containing environment was studied by means of potentiodynamic polarization and electrochemical impedance spectroscopy.The results show that the high entropy alloy has strong passivation ability in the environment containing hydrogen sulfide,and the corrosion of the high entropy alloy is accelerated with the increase of H₂S concentration.In the presence of H₂S,the protection of passivation film of high entropy alloy decreases with the increase of applied potential,and the protection of passivation film is poor.XPS results show that the main components of passive film in H₂S free solution are Cr₂O₃,CoO,Fe₂O₃,FeO,Fe₃O₄ and TiO₂,while in H₂S solution,the main components of passive film are Cr₂O₃,CoO,TiO₂,FeS₂,FeS,NiO and Fe₂O₃.The appearance of NiO in the passivation film indicates that Ni participates in the formation of the passivation film in the presence of H₂S.