Influence Factors And Mechanism Of Fe-ni-based Alloy 028 On Stress Corrosion Cracking In High Temperature And High Pressure H₂S/CO₂ Environment

With the sharp increasing in demand for domestic oil and gas resources,a large number of nickel-base corrosion resistant alloy are applied to highly acidic oil and gas well equipment manufacturing,thus the domestic production of nickel-based alloys has major economic implications for the cost savings.For the corrosion of nickel-base alloys,the stress corrosion cracking,as the biggest potential threats,has drawn great attention in high acid sulfur gas fields.Currently the research on stress corrosion cracking of corrosion resistant alloys is rarely reported,especially there are many gaps about the corrosion of alloys in high temperature and high pressure sulfur environment.In this work,we study the hydrogen sulfide stress corrosion cracking sensitive and the effect of cold deformation,precipitate and Fe³⁺on stress corrosion cracking in HPHT environment.Finally we use the electrochemical methods to study the effects of different factors on electrochemical characteristics of nickel-based alloy.To begin with,using slow strain rate tension tests?SSRT?we study the stress corrosion cracking susceptibility of 028 Ni-base alloys in H₂S/CO₂ chloride environment at 130?and 205?.Research results show that the material has a very high stress corrosion susceptibility in this condition,and with the increase of temperature stress corrosion susceptibility have also increased.Cold deformation increases stress corrosion cracking sensitivity in the hydrogen sulfide environment.Precipitation is relatively little effect on SCC susceptibility,but from fracture analysis it can be seen that precipitates significantly weakening the grain boundary and grain boundary secondary cracks produced during the stretch.Further,using a standard four-point bending test,we study the stress corrosion cracking susceptibility of 028 Ni-base alloys?GR,9A?and the stress corrosion performance of materials after adding Fe³⁺in HPHT H₂S/CO₂ environment.There is lighter corrosion in the corrosion without Fe³⁺,and passing the stress corrosion test.There is severe corrosion in the corrosion with Fe³⁺,and GR sample passing the stress corrosion test,but 9A sample no passing the stress corrosion test.The polarization and electrochemical impedance spectroscopy analysis found that Fe³⁺speeds the cathode reaction,significantly reduce the electrochemical reaction charge transferring resistance to accelerate corrosion process.Finally using Electrochemical means we study the effect of cold deformation,precipitates,hydrogen sulfide,hydrogen,and load on electrochemical characteristics of nickel-based alloys.Cold deformation improves the corrosion resistance of nickel-base alloys,and corrosion potential increase,corrosion current density decrease,capacitance arc become large,carrier concentration decreases.Precipitation decrease corrosion resistance of nickel-based alloys,and corrosion potential reduces,corrosion current density increases,capacitance arc becomes small,carrier concentration increases.In conjunction with the fourth chapter concludes,it can be found that cold deformation improves the corrosion resistance of materials in a certain extent,but the stress corrosion performance is no better.Owe to the precipitates,the poor corrosion resistance of the material is not enough to cause the stress corrosion performance significantly reducing.