Study On Corrosion Resistance Of Nitrogen-containing Austenitic Stainless Steel

Nitrogen-containing austenitic stainless steel has a good application prospect in the fields of aerospace,marine engineering and petrochemical industry.With the continuous reduction of global nickel resources,the use of nitrogen instead of nickel to produce nitrogen-containing austenitic stainless steel has become a research hotspot.In this paper,optical microscopy?OM?,X-ray diffraction?XRD?,scanning electron microscopy?SEM?,Thermo-Cala software,electron backscatter diffraction?EBSD?and electrochemical test systems are used to analyze the temperature through sensitization.At 750?and 900?,grain boundary corrosion was carried out in oxalic acid and sulfuric acid-sulfur iron solution respectively,and the corrosion properties and mechanical properties of different nitrogen content austenitic stainless steels were studied.The results show:?1?The corrosion performance of nitrogen-containing austenitic stainless steel is affected by the nitrogen content.The corrosion performance of nitrogen-containing austenitic stainless steels with different sensitization treatments?temperature 750?,900??increases with the increase of nitrogen content.Nitrogen increases the stability and compactness of the passivation film at the grain boundary and lowers the grain boundary.The tendency of the precipitate to precipitate out increases the overall corrosion resistance of the substrate.?2?The mechanical properties of nitrogen-containing austenitic stainless steels are affected by the nitrogen content.The yield strength of austenitic stainless steel increases with the increase of nitrogen content.The austenitic stainless steel with a nitrogen content of 0.59%?550.7MPa?has a higher yield strength than the nitrogen austenitic stainless steel with a nitrogen content of 0.31%?524.7MPa?,the formation of a large number of annealed twins reduced the tensile strength and elongation of austenitic stainless steel with a nitrogen content of 0.59%to 10MPa and 12.4%,respectively,compared to a nitrogen content of 0.31%austenitic stainless steel.?3?The effect of compression interval on the corrosion performance of high nitrogen austenitic stainless steel.The austenitic stainless steel with 0.59%nitrogen content was subjected to compression test at 1100?for two different times?10s,60s,120s,180s,300s?.During the compression process,the deformation temperature was 1100?,which was not good for austenite.The stability of the structure,and the longer the compression time,the lower the ratio of the low angle“coincidence lattice”of the low-angle grain boundary from 79.46%to 41.95%,and the occurrence of a small amount of?-?transition and the precipitation of precipitation of M₂₃C₆along the grain boundary.The corrosion resistance was the worst at intergranular corrosion at 300 s,resulting in an increase in the interval.The lower proportion of low-angle grain boundaries can not effectively interrupt the connectivity of corrosion-resistant grain boundaries and weaken the corrosion resistance of the intergranular.?phase and M₂₃C₆ are mainly precipitated by thermal exposure for a long time,while M₂₃C₆ is the main factor leading to intergranular sensitivity.The carbon of M₂₃C₆ will transfer the chromium atom near the grain boundary to the grain boundary,so that the vicinity of the grain boundary is in the chromium-depleted zone.It is not conducive to the stability of the inert passivation film and prevents the continued erosion of the corrosive medium.