Research On The Effect Of Adding High-carbon Ferrochrome On The Structure And Properties Of Laser Cladding Nickel-based Alloy Coatings

In the engineering application of most metal materials,wear,corrosion and other damage are easy to appear on the surface.To a certain extent,the using conditions and scope of materials are limited,and the service life of materials is shortened.Laser cladding technology can be used to improve the hardness and wear resistance of metallic materials by adding alloy powder with specific composition.A high power fiber laser combined with the coaxial powder feeding cladding method is adopted to obtain multichannel clad coating on the surface of metallic materials in order to improve the surface hardness,wear resistance and corrosion resistance,It has been paid much attention by scholars at home and abroad..In this paper,45#steel was used as the matrix,and the high carbon ferrochrome powder with the mass fractions of 0%,10%,20%,30%,40%,and 50%was added as the cladding powder in the Ni45 powder.The six laser cladding coatings were prepared by optimizing process parameters.The microhardness,microstructure,phase composition,wear resistance and corrosion resistance of the cladding layer were tested by microhardness tester,X-ray diffractometer,scanning electron microscope,transmission electron microscope,friction and wear tester,electrochemical workstation,etc.The main research results are as follows:Laser cladding of Ni45 powder was carried out with different process parameters,the hardness,dilution rate,thickness and lap ratio of the coatings were tested.The results show that the hardness of the coating is up to 386.1 HV,the dilution rate is 19.4%,the coating thickness is 0.48 mm,and the microstructure is even fine at the power of 2000 W,the melting rate of 6 mm/s,the powder feeding rate of 14g/min and the lap ratio of 35%.Therefore,it is determined that the above parameters is the best parameter for the later laser cladding experiments with high carbon ferrochrome powder.Under the best experimental parameters,a high proportion of high carbon ferrochrome powder cladding was prepared by multi-channel lap.The bonding between coating and substrate is metallurgical bonding,whose strength is high.The microstructure of the cladding layer is followed by planar crystal,cellular crystal,columnar dendrite,fine dendrite and fine equiaxed crystal.The main phases are?-Ni solid solution,Cr₂₃C₆,CrB.With the increase of the content of high carbon ferrochrome,the hardness of cladding layer is also increasing.When the added content is 30%,the average hardness reaches a certain peak value of about 483 HV,which is 1.26 times for unadded cladding layer?384HV?and 2.54 times for matrix?190 HV?.At this time,the grain structure is also the smallest.It indicates that adding a certain amount of high carbon ferrochrome can refine grain and increase hardness.Hardness almost no longer increase and the grain begin to coarsen by continuing to add high carbon chromium iron.Through TEM analysis,it is known that the hard phase particles in the cladding layer are Cr₂₃C₆,and the microhardness value is about1650 HV,which improves the hardness of the cladding layer to a certain extent.The wear resistance of the prepared cladding layer is excellent.When the content of high carbon ferrochromium is 30%,the roughness and depth of wear marks are the smallest.The weight loss of the cladding layer is 2.1 mg,and the weight loss of the pure Ni45cladding layer is 6.1 mg,so the loss weight is about 34.4%of the Ni45 cladding layer,that is,the wear resistance is about 2.9 times higher than that of the Ni45 cladding layer.But when the content of high carbon ferrochrome continues to increase,the weight loss will increase.This indicates that the content of high carbon ferrochrome is not the more,the better.There is a best value,in this experiment,the best addition is 30%.The electrochemical test shows that the corrosion resistance of the coating obtained when adding 30%high carbon ferrochrome is best.It has the lowest corrosion current density?2.03E-7 A/cm²?;Salt spray test results show that the 30%addition of the cladding layer has the smallest corrosion area,and its corrosion rate is 0.2 mg·dm^-2 h^-1,which is lower than the corrosion rate of the Ni45 cladding layer(0.5 mg·dm^-2 h^-1).