316L钢在超临界水拟临界区内的 蚀行为特性研究

To study the corrosion behavior of metal materials in the pseudocritical region of supercritical fluid and explain the corrosion intensification mechanism in such a region, the corrosion experimental platform of supercritical fluid reactor was used for the static corrosion test of 316L austenitic stainless steel for 200h under three supercritical conditions(375.6 ℃-22.5 MPa, 405.6 ℃-22.5 MPa, and 405.6 ℃-28.6 MPa). The corrosion behaviors of the 316L stainless steel were analyzed by weighing with electronic balance, scanning electron microscope, energy dispersive X-Ray spectroscopy and X-Ray diffraction. The results show that 316L stainless steel has the highest corrosion rate and the most complex corrosion products in the pseudocritical region(375.6 ℃-22.5 MPa). The corrosion products in such a region are two layers, of which the outer layer is Fe₃O₄and Fe₂O₃and the inner layer is FeCr₂O₄. However, only one layer of Fe₃O₄is formed in the supercritical high pressure parameter region(405.6 ℃-28.6 MPa), and the inner product film has not been formed. Through the analysis of corrosion mechanism, it is found that the physical properties of supercritical water change dramatically and the dynamic effect is enhanced in the pseudocritical region. This phenomenon accelerates the migration of corrosive media such as oxygen to the material matrix, and intensifies the abscission and dissociation of corrosion products. Therefore, the corrosion of materials in the pseudocritical region is intensified. This study provides a scientific basis for improving the corrosion resistance of materials in supercritical fluid environment and the safe operation of supercritical system in China.