Study On The Structure And Wear Resistance Of Laser Cladding Fe60/WC Composite Coating On 65Mn Steel Surface

Wear is one of the main factors leading to the failure of soil contact components in agricultural machinery.The rotary tiller blade is susceptible to wear and tear from soil,sand,and weeds during operation,resulting in the blade being prone to failure due to wear and tear.This not only reduces the efficiency of tillage,but also increases the cost of tillage.With the advancement of agricultural mechanization,more and more attention has been paid to the surface wear resistance treatment of agricultural machinery contact parts both domestically and internationally.Therefore,improving the wear resistance of the surface of rotary tillers is of great significance for improving the production efficiency of agricultural mechanization.This article selects 65Mn steel commonly used in domestic rotary tillers as the matrix material,and uses laser cladding method to prepare Fe60/WC composite cladding layer on its surface.We studied the effects of three main process parameters in laser cladding technology:laser power,scanning speed,and overlap rate on the microstructure and properties of the cladding layer,and optimized the process parameters.And using WC ceramic particles as the reinforcing phase,a Fe60/WC composite cladding layer was prepared on the surface of 65Mn steel under optimized process parameters.The microstructure,microhardness,wear resistance,strengthening mechanism of WC particles,and wear mechanism of the coating were discussed using metallographic microscopy,laser confocal microscopy,Vickers microhardness tester,scanning electron microscopy,X-ray diffractometer,and friction and wear tester.The main research content and conclusions are as follows:（1）In order to explore the influence of process parameters on the cladding layer,9experimental schemes with different laser power and scanning speed combinations were designed.The experimental results show that laser power and scanning speed have a significant impact on the dilution rate and microstructure of the cladding layer,and the effect of laser power is more significant.The dilution ratio and grain size increase with the increase of laser power,and decrease with the increase of scanning speed.Based on the experimental results of surface forming quality,elastic modulus,and surface microhardness,the appropriate experimental parameters were determined:laser power of1200 W,scanning speed of 7 mm/s.（2）Under the above experimental parameters,different lap rates were selected for multi pass cladding of 65Mn steel.The experimental results show that as the overlap rate increases,the grain size of the cladding layer gradually increases,the surface hardness gradually decreases,and the powder utilization rate increases.Through comprehensive evaluation,50%overlap rate is the most suitable choice,and its surface forming quality is the best.There is no obvious accumulation or groove,and the microhardness is 1118.71HV.（3）By characterizing the distribution and dissolution of WC particles,as well as analyzing the microstructure inside the cladding layer and the distribution of elements around WC,it was found that excessive WC content can lead to sedimentation in the middle and lower parts of the cladding layer.WC particles will dissolve in the molten pool,and the dissolved WC will serve as the nucleation substrate to promote grain refinement.The decomposed W and C elements will react with other elements in the molten pool to form new hard phases（WC,W₂C,and Fe₃W₃C）,which strengthen the cladding layer.The hardness of the composite cladding layer increases with the increase of WC content.（4）The wear resistance of Fe60/WC composite cladding layer was studied using the experimental method of reciprocating friction and wear.Under the same wear conditions,the friction coefficient and wear volume of the composite cladding layer first increase and then decrease with the WC content.They are the smallest at a WC content of 30%,with a friction coefficient of 0.563 and a wear volume of 0.0109 mm³,which is 14%of the matrix wear amount.（5）Analyze the morphology and elements of the wear marks to determine the wear mechanism of the composite cladding layer.The wear mechanism of Fe60 cladding layer is oxidation wear and adhesive wear,accompanied by a small amount of fatigue wear.Compared with the Fe60 cladding layer,the wear behavior of the 20 wt.%WC cladding layer is mainly oxidation wear and a small amount of adhesive wear.The wear behavior of 30 and 40 wt.%WC cladding layers is oxidation wear,adhesive wear,and a small amount of abrasive wear.