Study On High Temperature Oxidation Behavior And Mechanism Of 310S Stainless Steel Screen Wire Mesh

Because of its highly chromium&nickel contents,excellent corrosion resistance,acid and alkali resistance,especially resistance to high temperature oxidation above800?temperature,310S austenitic stainless steel wire mesh has been widely used as screening filters and protective devices of special service environments in the industries of petrochemical,food and medicine,aerospace,automotive ships,nuclear power and military industries,etc.With the strengthening of environmental protection and increasing the automobile exhaust emission standards,higher working temperature for the exhaust system is required.So that higher requirements are put forward for the high temperature oxidation resistance of 310S SS sreeen wire mesh used in the exhaust systems.In order to ensure the excellent high temperature oxidation resistance and reliability of 310S SS wire mesh in service,cyclic oxidation methods at 1050?constant temperature were used to analyze and evaluate high temperature oxidation resistance of samples which are the same specification and different batches,and factors affecting the difference in high-temperature oxidation resistance were explored in this paper.The influences of alloying elements on the precipitation and contents of equilibrium phases at different temperatures were simulated and analyzed by JMatPro software.The continuous oxidation method was used to study the kinetic curve of continuous oxidation of the wire mesh at different temperatures,and the kinetic equation was established.SEM,XRD,EDS and other methods were used to characterize oxide films in order to study high temperature oxidation behavior and oxidation mechanism of 310S SS wire mesh.The main conclusions are as follows.High-temperature cyclic oxidation experiments showed that oxidative weight gains of P1 and P3 specimens after two cycles at 1050? were less than 3.5%indicating qualified products.Weight gains of the other four samples in the two cycles exceeded 3.5%meaning unqualified products.Among them,P2 sample had the largest oxidation weight gain in the two cycles,reaching 7.74%,which was more than 1.3 times above the limit of qualified specification.SEM microscopic morphological characterization showed that the oxide film formed on the surface of P1 qualified mesh after the first cycle at 1050? was flat,very fine and homogeneous.It's very dense and evenly covered after the second cycle,and crystal grains grow slightly which the oxide film being densely arranged tetrahedrons and flakes.Grain sizes of the oxide film formed after the first cycle for unqualified P2 sample is comparable to that of the qualified screen in the same cycle,but the surface flatness is slightly worse.The morphology of oxide film after the second cycle was porous and honeycomb with loose oxide film and somewhere peeling.XRD,EDS and chemical composition analyses indicated that the surface oxide film of P1 sample is mainly composed of fine uniform Cr₂O₃ particles after the first oxidation cycle at 1050?,which a dense oxide film of MnCr₂O₄ and NiCr₂O₄ with spinel structure was formed during the second oxidation cycle.However for P2 unqualified sample,the surface oxide film is mainly composed of loose,porous and poorly stabilized Fe₂O₃ and Fe₃O₄ during two oxidation cycles.The main reasons for the poor high temperature oxidation resistance of P2 sample is related to the chemical compositions with slightly higher carbon content and lower Cr,Si,Ni and Mn content in it,resulting in the formation of unstable oxide film due to the element lack of chromium,and its high temperature oxidation resistance decreases.The appropriate content of Si in materials may be combined with oxygen to form a more stable SiO₂ oxide film in the inner layer could prevent oxygen atoms attacking the matrix and plays a positive protective role for high temperature oxidation resistance.Continuous oxidation experiments for qualified P3 and unqualified P6 samples at different temperatures showed that they were both possessing good high temperature oxidation resistance during the experiment period at 850? and 950?.The oxidation kinetic curves of samples at 850? were in accordance with the straight line rule which meaning the oxide film growth mainly controlled by the interfacial reaction rate between the alloy and oxygen atoms,and the oxidation rate is very low.Oxidation kinetic curves during 950? and 1050? continuous oxidation were in accordance with the parabolic rule which oxidation kinetics were mainly affected by the diffusion rate of the elements through the oxide layer.The weight gain of the oxide film is mainly affected by the diffusion reaction rate of oxygen atoms through the oxide film.With the temperature rising,the oxidation reaction rate increases significantly.The parabolic constant of of P6oxidation kinetic curve at 1050? was more than twice that of P3 curve.The main reason was the loose,porous and non-compact iron oxide fime formed at 1050? for P6 wire mesh which increasing the diffusion of oxygen atoms,and resulting in a sharp increase in weight gains and poor oxidation resistance,while the dense and spinel structure of rich Cr oxide film formed for P3 sample making it better high temperature oxidation resistance.JMatPro thermodynamic simulation results show that the basically phase for both qualified sample P1 and unqualified one P2 is a single-phase austenite in the range of temperature 1000? to 1050?.The increasing of carbon content leads to the presence of a small amount of M₂₃C₆ carbides in high temperature phase region,which would reduce the Cr content in austenite and affect its high temperature oxidation resistance.When the temperature is lower than 890?,the brittle?phase and M₂₃C₆ carbide increase as the temperature decreasing,,and the brittleness of SS wire meshes increasing.The increase of Si element content delays the complete austenitization temperature of 310S SS to higher temperature which improving the high-temperature oxidation resistance of 310S stainless steel.Ni,Mn alloying elements also affect the stability of the austenitic phase at high temperatures,resulting in differences in the high temperature oxidation resistance of wire meshes.