Study On Microstructure And Properties Of Fe-Cr-M Alloy And Coatings Prepared By Laser Modification

Using high-carbon ferrochrome as doped component,Fe-Cr-M alloy and coatings were prepared by laser rapid processing technology.The microstructure,morphology and phase structure of the sample were analyzed by optical microscope,X ray diffractometer,scanning electron microscope and energy spectrum analyzer.The micro-hardness,wear resistance and corrosion resistance of the coatings and sintered alloy were analyzed by means of micro-hardness tester,wear test machine and electrochemical workstation.The main contents are as follows:(1)The high-carbon ferrochrome powder with mass fraction of 0%,25%,50%,75%and 100%were uniformly mixed with the Ni35 self-fluxing powder.The Fe-Cr-Ni coating was prepared on the surface of 27SiMn steel by laser cladding.The effects of coating composition,laser scanning speed and laser power on the microstructure and properties of the coatings were investigated.The experimental results show that:from the outside to the inside,the coatings are respectively fine grain zone,the columnar zone,bonded zone and heat affected substrate.The coating and the substrate are metallurgical bonded.When the content of high-carbon ferrochrome is 50%,the content of lath shaped tissue in the middle zone of the cladding layer become more and its distribution is uniform.The coating phase mainly consists of ?-Ni??-Cr?FeNi3?Fe3Ni2?Cr2Ni3 and(Cr,Fe)7C3.When the content of high-carbon ferrochrome is 50%,the micro-hardness of coating is higher and the distribution is uniform.At the same time,the corrosion current density is minimum.When the content is 100%.the wear rate is the lowest.With the increasing of scanning speed,the micro-hardness increases and the wear rate decreases.When the scanning speed is 3 mm/s,the corrosion current density of cladding layer is the smallest.With the increase of laser power,the micro-hardness of the cladding layer changes little,and the wear rate reaches the maximum at 1900 W.(2)The high-carbon ferrochrome powder with the atomic fraction of 5%,10%,15%,20%and 25%were mixed with aluminum powder evenly and pressed compact.Fe-Cr-Al alloy is prepared by laser induced self-propagating sintering.The effects of different content of high-carbon ferrochrome on the sintered alloy microstructure and properties and the change of microstructure and properties of upper layer,middle layer and bottom layer were studied.The experimental results show that:When the content of high-carbon ferrochrome is 20%,the porosity is the smallest and the density of sintered alloy is the biggest.The phases of sintered alloys mainly consists of ?-Al,Fe2AlCr,Al13Fe4,Al13Cr2 and Al2O3.With the increase of the content of high-carbon ferrochrome,the microstructure of middle layer changes from nonuniform block to fine uniform granular.When the content is 20%,the microstructure of the middle layer of the alloy is fine and uniform,and the pores are less.And the micro-hardness values of each layer of the sintered alloy have the maximum value,the wear rate of each layer reaches the lowest value and the corrosion current density is the smallest.