High Temperature Oxidation Behaviors Of New Heat-resistant Stainless Steels

With the rapid development of China's high-end equipment manufacturing industry,the demand for heat-resistant stainless steel used in high temperature environment is increasing day by day.At present,the service performance of heat-resistant stainless steel in China is more and more demanding,especially for the oxidation performance at higher temperature requirements are more stringent,because good oxidation resistance at high temperature is the key factor to ensure the life and safety of stainless steel in the use process.By studying the oxidation performance of heat-resistant stainless steel at high temperature,we can further improve the performance of heat-resistant stainless steel,expand its application field,and lay the foundation for improving the oxidation performance in the future.The experimental materials used in this paper are improved domestic austenitic stainless steels 309S,310S and ferritic stainless steels X10Cr Al Si18,which are named as 309SMOD,310SMOD and new ferritic heat-resistant stainless steels X10Cr Al Si18.Oxidation tests were carried out at high temperatures of 800?,900?and 1000?.By means of SEM,EDS and XRD,the structure,morphology and specific phase composition of the oxidation products of heat-resistant stainless steel were analyzed,and the oxidation mechanism at high temperature and the influence of different parameters on oxidation behavior were analyzed by using oxidation kinetics and oxidation thermodynamics theory.The main results are as follows:(1)The oxidation weight gain curve of the austenitic stainless steel309SMOD conforms to the parabola law,and it has oxidation resistance.With the increase of oxidation temperature and oxidation time,the weight gain of the sample increases gradually.According to the oxidation rate diagram,with the increase of oxidation temperature,the oxidation rate of the sample decreases gradually.Among the three oxidation temperatures,the minimum value of parabolic rate constant K_pat 800?is 0.0000374mg²·cm^-4h^-1,the maximum value of parabolic rate constant K_p at 1000?is 0.000286mg²·cm^-4h^-1,the antioxidant performance is poor.At 800?,the oxides are mainly plate-like and small spinel,while at 900?and 1000?,products are mainly spinel particles.With the increase oxidation temperature,platy oxide is transformed into spinel particles.(2)The oxidation weight gain curve of austenitic heat-resistant stainless steel 310SMOD also conforms to the parabolic law.The maximum oxidation rate of 310SMOD at 800?is 0.0021g/m²·h.The maximum oxidation rate at900?is 0.0032g/m²·h;the maximum oxidation rate at 1000?is 0.008g/m²·h,and the oxidation rate is less than 0.1g/m²·h.The oxidation resistance level belongs to the complete oxidation resistance level.At 800?,the oxides are mainly plate-like and small spinel.At 900?and 1000?,the oxide film falls off.With the increase of temperature,the spinel particles gradually increase.(3)The oxidation kinetics curve of the new ferritic heat-resistant stainless steel X10Cr Al Si18 conforms to the parabola law,it has antioxidant properties.The maximum rate at 800?was 0.0023g/m²·h,900?was 0.004g/m²·h,and1000?was 0.005g/m²·h.The oxidation rates were all less than 0.1g/m²·h.The antioxidant grade was complete antioxidant grade.At 800?and 900?,there are pits on the surface of the oxide film,and the oxides are mainly vermicular and spinel.At 1000?,there are cracks on the surface of the oxide film,and the oxides are mainly spinel particles.(4)The oxide film of austenitic stainless steel is divided into three layers,the outermost layer is the thick spinel structure of Mn Cr₂O₄,the middle layer is dense Cr₂O₃,the innermost layer is the oxidation of Si O₂ in the matrix.X10Cr Al Si18 oxide film is divided into three layers,the outermost layer is spinel structure of Mn Cr₂O₄ and Fe-Cr oxide,the middle layer is Al₂O₃,the innermost layer of oxide is Si O₂.(5)Under the same oxidation conditions,the oxidation rate constant K_p of309SMOD is smaller than that of 310SMOD,indicating that 309SMOD has better performance.By comparing and analyzing the new type of ferrite X10Cr Al Si18 and the common ferrite X10Cr Al Si18,it is found that the new type of ferrite stainless steel has better oxidation resistance at high temperature,and the effect is more obvious when the temperature exceeds 900?.