Study On The Precipitation Behavior Of Carbides On The Grain Boundary Of 5Cr15MoV Martensitic Stainless Steel

Carbide is an important constituent phase in martensitic stainless steel.The distribution of carbide in steel has an important effect on the properties of steel.At present,the control of carbide precipitation and growth has been studied at home and abroad,but there are few reports on the study of carbide orientation and control.Therefore,this paper takes 5Cr15MoV martensitic stainless steel as the research object,studies carbide precipitation and growth by changing single factor variables,and explores the relationship between orientation information and carbide precipitation evolution at grain boundary by using electron backscatter diffraction?EBSD?technology.The main contents and conclusions of this paper are as follows:The static continuous cooling transition curve of 5Cr15MoV steel was obtained by gleeble-3800 thermal simulation machine experiment,and the final solidification structure of 5Cr15MoV steel was ferrite,martensite,residual austenite,M₂₃C₆ and M7C3 carbides,mainly grain boundary carbides M₂₃C₆.In addition,with the increase of cooling speed during the cooling and solidification process,the width of the poor Cr area near the grain boundary of 5Cr15MoV stainless steel was shortened from 0.871 ?m to 0.569 ?m,the concentration gradient was reduced from 36.422% to 12.667%,and the growth rate of carbide nuclei was reduced by 66%.The size of carbide M₂₃C₆ at grain boundary was refined.The corrosion test shows that with the increase of the cooling rate,the corrosion current density decreases from 13.29 ?A/cm² to 2.42 ?A/cm²,and the corrosion rate decreases from 218.339 mm/a to 158.488 mm/a,which weakens the intergranular corrosion and pitting corrosion and improves the corrosion resistance of 5Cr15MoV steel.In the process of inhomogeneous nucleation,the interface energy will be generated,which will affect the size of the new nucleation.Through the collection and analysis of the contra-directional difference,it is found that the optimal small-angle grain boundary of carbide nucleation is 3.05°,that is,the interface can be 0.2697 J/m2.Under the condition of 50% deformation,the proportion of small Angle grain boundary of precipitated carbide is the highest,the amount of carbide precipitation is the least,and the carbide size is the smallest.The grain size is also reduced to 0 ?m?10 ?m.