| Current energy demand is strong.In order to fulfill the urgent needs of the national economy and to meet the requirements and challenges of environmental protection,it is necessary to develop high-capacity and high-parameter ultra supercritical power generation technology.Ferritic heat-resistant stainless steel has the advantages of low cost,small thermal expansion coefficient,high thermal conductivity and good comprehensive mechanical properties.However,with the continuous development of thermal power technology,the existing ferrite heat-resistant stainless steel has been unable to fulfill the future large-capacity and high-parameter ultra supercritical power generation technology requirements,people are trying to develop new ferrite heat-resistant stainless steel through various ways to improve its performance.X10CrAlSi18 steel is a high-Cr ferrite heat-resistant stainless steel with 18% Cr content and the addition of Al and Si elements in the steel can form a dense chromium,has been put into production in foreign countries.But the domestic application of the same kind of material depends entirely on imports,and in China and abroad on the steel structure and performance has less research,it is necessary for the steel systematically studied in order to more secure use.In this paper,ferritic heat-resistant stainless steel X10CrAlSi18 was used as experimental materials and scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),X-ray diffraction(XRD)and tensile experiments were used to study the microstructure and properties.The study mainly includes the effect of heat treatment system on the organization and properties and the anti-high temperature oxidation behavior of X10CrAlSi18.The experimental results were as follows:The thermodynamic equilibrium phase diagram is calculated by Thermo-Calc software,which can help to analyze the microstructure changes under different heat treatment conditions.The results show that X10CrAlSi18 heat resistant steel in the heat treatment process,AlN phase,M7C3 carbide,M23C6 carbide and Sigma phase will produce in the matrix.In order to adjust the organization and relieving of internal stress,improve the processing performance of the material,so the steel should be annealed and tempered treatment.When annealing between 800?950 ?,the microstructures are mainly ferrite phase,M23C6 carbide,Sigma phase and AlN phase.When the annealing temperature is 850 ?,the steel structure is more uniform,the average grain size is 48.91 ?m,and it has excellent structure and properties.As the ferrite stainless steel with low temperature brittleness,to master its ductile and brittle transition temperature can provide a reference for the actual production and processing,so the steel ductile ductile transition temperature test.The ductile-brittle transition temperature test shows that the ductile-brittle transition temperature of X10CrAlSi18 steel is about 87 ?.High temperature oxidation resistance is an important indicator of the performance of heat-resistant steel.In this paper,the steel was subjected to high temperature oxidation test by constant temperature oxidation,the test temperature is 800 ?,900 ? and 1000 ?,and the sampling time interval is 20 h.The oxidation weight gain curve of X10CrAlSi18 steel is in accordance with the typical parabolic law.The oxidation weight gain at 1000 ? is significantly higher than that of 800 ? and 900 ?.The oxidation resistance of ferritic heat-resistant stainless steel X10CrAlSi18 at 800 ? and 900 ? is completely antioxidant and the oxidation resistance of 1000 ? is antioxidant.The morphology and phase composition of the oxide layer were analyzed by XRD,SEM and EDS.It shows that the oxide layer is composed of MnCr2O4,SiO2,Al2O3 and(Fe0.6Cr0.4)2O3 oxide at 800~1000 ?,but the oxide layer is mainly spinel structure MnCr2O4 oxide at 800 ? and 900 ?.While the oxide layer is mainly composed of spinel structure(Fe0.6Cr0.4)2O3 oxide at 1000 ?.The conversion from Cr/Mn oxides to Fe/Cr oxides is the main reason for the decrease of oxidation resistance. |
PDF Full Text Request