Microstructure And Wear Resistance Of Laser Cladding Al_1.8CrCuFeNi₂ High Entropy Alloy Coating

In order to improve the wear resistance of soil contact parts of agricultural machinery,Al_1.8CrCuFeNi₂ high entropy alloy coating was prepared by laser cladding technology on 65Mn spring steel substrate.The effects of process parameters(including different cladding power and different cladding layers)on the microstructure and wear resistance of high entropy alloy coating were analyzed.TiC reinforced particles were added into the high entropy alloy powder,and the effect of TiC content on the microstructure and wear resistance of the coating was studied and its mechanism was analyzed.The microstructure,hardness and wear resistance of the coating were investigated by metallographic microscope(OM),X-ray diffractometer(XRD),scanning electron microscope(SEM),energy dispersive spectroscopy(EDS),micro hardness tester and ring-block sliding friction tester.The main results are as follows:The influence of cladding power(1100W,1500W,1900W)on the microstructure and wear properties of the coating was studied.The results showed that the three power cladding coatings all had BCC solid solution structure,and the grains were mainly equiaxed columnar crystals,among which the grains of 1100W coating were the smallest.The elements on the coating surface were evenly distributed without obvious segregation.The coating and matrix of three kinds of power were combined in metallurgical way,and the gradual change of elements on the bonding surface was relatively gentle.It was found that the hardness of the coating prepared by1100W power was the highest,which was 843.3HV.The hardness of 1500W and 1900W was681.9HV and 717.4HV,respectively.The friction coefficient of 1100W power coating was the lowest and the most stable,and the wear amount of 1100W,1500W and 1900W coating at30min was 11.7mg,12.6mg and 12.5mg,respectively.It could be seen that the hardness and wear resistance of the coating prepared by 1100W power were the best,which were related to the fine grain size and uniform distribution of elements.The influence of the number of cladding layers(single layer,double layer,three layer,four layer)on the microstructure and wear properties of the coating was studied.The four kinds of coatings were mainly BCC solid solution structure,and the phase structure was the same.It was found that the grain structure of monolayer and double layer cladding was more complete and the element distribution was more uniform.The grains of the three-and four-layer cladding coatings changed from equiaxed dendrites to petal-like dendrites,while the defects increase and elemente segregation occurs.The hardness of the coating was similar with the number of layers,but the wear amount was different.The hardness of double-layer cladding was 931.5HV.The hardness of single-layer,three-layer and four-layer cladding was 766.5HV,812.2HV and847.4HV,respectively.At 30min,the wear amount of double-layer cladding was 11.7mg,and that of single-layer,three-layer and four-layer cladding was 16.3mg,31.2mg and 29.5mg,respectively.Therefore,the coating prepared by double-layer cladding had the best wear resistance,due to the moderate thickness of the cladding layer and the uniform distribution of elements.The microstructure and wear properties of the coatings reinforced with 10%,20%and 30%TiC were studied.After the addition of TiC,the microstructure of the coating had a great change,especially when the TiC content reaches 20%and 30%,the massive dispersion phase was generated.The results showed that the hardness of coatings increased with the increased of TiC content.The hardness of BCC phase in 10%TiC,20%TiC and 30%TiC coatings were 865.2HV,947.9HV and 969.6HV,respectively,which were 145.3%,168.8%and 174.9%higher than that of matrix materials,respectively.The hardness of TiC dispersion phase precipitated from20%TiC and 30%TiC coating was 2645.4HV and 3408.5HV,respectively.The wear mechanism of the three TiC coatings with different content of TiC was abrasive wear,and the wear amount decreases with the increase of TiC content,and the wear amount of 10%,20%and 30%TiC coatings was 11.3mg,2.1mg and 2.2mg when worn for 30min.2 hours of 10%,20%,30%TiC coating wear 36.5mg,9.1mg,8.1mg.However,the 30%TiC coating had high brittleness and produces too many cracks,so the optimal TiC content was 20%.In general,the 65Mn spring steel matrix coating prepared with 1100W cladding power,double cladding,Al1.8Cr Cu Fe Ni2+20%TiC(wt.%)powder had the best wear resistance,the material had important application prospect in wear-resisting parts of agricultural machinery...