Study On Microstructure And Strengthening Of Fe-36Ni Invar Alloy Cladding Coating By Laser Cladding On 42CrMo Steel

As the main part of the steel rolling equipment,the roll not only has to withstand huge extrusion stress and shear stress but also withstand huge thermal stress during the working process.In this working environment,rolls are prone to failure forms such as wear,peeling,and fracture.The failure of the roll will not only increase the production cost but also affect the production efficiency of the steel and the accuracy of the final product.To reduce the production cost of iron and steel enterprises,the use of laser cladding technology to repair the roll failure surface has broad application prospects.In the laser cladding process,internal stress is often generated due to the difference in thermal expansion coefficient between the cladding coating and the base material,which leads to the formation of cracks in the cladding coating.The low expansion performance of Invar alloy can effectively reduce the tendency of cracks in the cladding coating.In this paper,a low-crack invar cladding coating was prepared on the surface of42CrMo steel matrix by laser cladding technology,and the structure and performance of Fe-36Ni invar alloy cladding coating under different process parameters were studied.The Cr element and WC strengthening factors were further carried out.For the study of cladding coating of watt alloy,use optical microscope(OM),scanning electron microscope(SEM),energy spectrometer(EDS),and X-ray diffractometer(XRD)to analyze the microstructure and phase composition of the cladding coating,And analyzed the microhardness,friction and wear and corrosion resistance of the cladding coating.The main research contents and conclusions are as follows:1?First,the microstructure and properties of the laser cladding Fe-36Ni Invar alloy cladding coating were studied,and the effects of laser power and scanning speed on the microstructure and properties of the Invar alloy cladding coating were analyzed.The analysis results of sensitivity,microstructure,and mechanical properties are used for parameter optimization.The results show that the optimal process parameters are as follows:laser power 1400W,scanning speed 4mm/s,spot diameter 4mm.The crack sensitivity of the cladding layer is low.The microstructure of the cladding layer changes from plane dendritic to cellular and columnar dendritic to equiaxed from the bottom to the top.The phase of the cladding layer is mainly composed of Fe_0.64Ni_0.36phase of fcc structure and?-[Fe,Ni]austenite phase.Compared with 42CrMo steel matrix,the mechanical properties of Intile alloy cladding coating are poor.2?Then,the microstructure and properties of laser cladding coating strengthened by Cr element were studied.The effects of Cr element on the macroscopic morphology,microstructure,phase,microhardness,wear resistance,and corrosion resistance of the cladding coating was analyzed.The results show that with the addition of Cr,the dilution rate and wetting angle of intile alloy cladding coating change.When Cr content is 6%,the wettability of the cladding coating is the best.With the increase of Cr content,the grain size of the cladding coating decreases first and then increases.The grain structure is the smallest when the Cr content is 6%.The combined XRD and EDS analysis results show that the addition of Cr promotes the formation of ferrite in the cladding coating and affects the Invar effect of the cladding coating.The microhardness of the cladding coating increases with the increase of the Cr content,and the wear resistance and corrosion resistance performance are also improved with the increase of the Cr content.3?Finally,the microstructure and properties of WC/Fe-Ni-Cr alloy cladding coating enhanced by WC laser cladding were studied,and the effect of spherical WC content on the macroscopic morphology,microstructure,and properties of Fe-Ni-Cr alloy cladding coating was explored.The results show that the addition of spherical WC inhibits the formation of?-[Fe,Ni]and Fe_0.64Ni_0.36 phases in the fcc structure,and promotes the increase of Fe-W-C compounds in the cladding coating.With the increase of spherical WC content,the grain structure of the cladding coating becomes finer and finer.When the spherical WC content is 20%,the grain size in the middle of the cladding coating is the smallest.The microhardness of the cladding coating has been significantly improved with the increase of the spherical WC content.When the WC content is 20%,the microhardness of the cladding coating is 508HV_0.2,which is about2.1 times that of the 42CrMo base material.The friction coefficient and wear amount of the cladding coating decrease with the increase of the spherical WC content and the wear resistance is improved.The corrosion resistance of the cladding coating increases first and then decreases with the increase of WC content.When the spherical WC content is 10%,the corrosion resistance is relatively better.In this paper,the low crack Fe-36Ni alloy cladding coating was successfully prepared and strengthened.The purpose of this study is to solve the crack problem caused by thermal stress in the process of cladding coating and to provide reference for the research of laser cladding and strengthening of tile alloy cladding coating.