Wear Behavior of CO2 Corrosion Scales on Well Tube Steel N80 in Water-Sand Two-Phase Fluid Medium

An autoclave was used to simulate the corrosion behavior of N80 steel in CO_2 atmosphere at elevated temperature and pressure. The wear behavior of the resulting CO_2 corroded product scales on the N80 steel in a water-sand two-phase fluid medium was examined on a test rig designed in our lab. The correlations among the wear behavior of the scales and the temperature and CO_2 pressure at which the scales were formed, and the flowing velocity and sand granularity of the two-phase fluid medium, were investigated. Thus the surface roughness of the original scales was determined using a profilometer, while the worn surfaces and cross-sections of the scale were observed using a scanning electron microscope. Results indicated that the surface roughness of the original corrosion product scales was dependent on the temperature and CO_2 pressure for the simulating corrosion tests, and the morphologies of the worn surfaces and cross-sections of the scales varied with varying wear depths, which corresponded to the differences in the microstructures, especially the grain granularity and compactness of the scales. Moreover, the erosion-wear behavior of the scales was also dependent on the flowing velocity and sand granularity of the two-phase fluid.