| High entropy alloy has high strength,high hardness,high wear resistance,high temperature oxidation resistance,corrosion resistance and excellent thermal stability,which has potential engineering application prospect.However,the high-entropy alloys developed by the industry are mostly bulk materials,which are not only limited in size,but also prone to various metallurgical defects,and the preparation process requires a large amount of high-value components such as Co and Ni,and the production cost is high.However,surface engineering technology can produce complex parts by preparing cladding layers with special properties on the surface of mechanical parts without expensive molds.Therefore,preparing high entropy alloy as cladding material in surface engineering technology can not only give full play to the excellent characteristics of high entropy alloy,but also greatly reduce the cost,improve the utilization rate,and greatly expand the application range of high entropy alloy.Based on this,this paper adopts plasma cladding technology to use nickel aluminium bronze(NAB)and 304 stainless steel as substrates and FeCoNiCrMnAl0.5(labeled Al)and FeCoNiCrMnAl0.5Si0.5(labeled AS1)high entropy alloys as cladding materials.The A1 and AS1 cladding layers were prepared respectively,and the optimum process parameters,organization and properties of the cladding layers were investigated.Finally,the feasibility of the AS1 clad layer in the application of engineering machinery seal ring surface repair was explored.Firstly,the process optimisation,microstructure,hardness and corrosion resistance properties of the melt clad layers were explored using NAB applied in corrosive environments as the substrate and A1 and AS1 as the melt clad layer materials.It was found that too little current leads to poor bonding of the powder to the base material and poor surface saturation;too much current results in an increase in the depth of melt,wider weld channels and signs of oxidation on the weld channel surface.Too little powder feed speed will result in a poorly saturated surface and a too thin weld thickness;too much powder feed speed will result in a too high weld thickness and a too saturated weld layer.The gun speed is too small,resulting in too high a weld channel thickness and too deep a melt pool;the gun speed is too large,resulting in too thin a clad layer and poor saturation.A1 and AS1 clad layers are both composed of the physical phase FCC+BCC+σ phase.The average surface hardness of the cladding layer is more than twice the average hardness of the NAB base material(1 82.5 HV).Frictional wear tests show that the wear mechanism of the A1 clad layer is adhesive wear and abrasive wear,while the wear mechanism of the AS1 clad layer is abrasive wear;the wear resistance of the A1 clad layer<NAB<AS1 clad layer.The electrochemical corrosion experiments revealed that the corrosion resistance of the melt layer was better than that of the NAB base material,and the self-corrosion current density was lower than that of the NAB base,with the A1 melt layer having the best corrosion resistance.Secondly,the process optimisation,microstructure,hardness and corrosion resistance of the clad layers were investigated using the common mechanical component material 304 as the substrate and A1 and AS1 as the clad layer materials.It was found that the physical phase of the 304-A1 clad layer is mainly FCC+BCC phase and that of the 304-AS1 clad layer is FCC+BCC+σ phase.The hardness of A1 cladding layer is low,which is equivalent to that of 304(187.67 HV),and the friction coefficient fluctuates greatly.The wear mechanism is mainly abrasive wear and adhesive wear,and the wear resistance is poor.The hardness of AS1 cladding layer is high(717.9 HV),the friction coefficient fluctuation is relatively stable,the wear mechanism is mainly abrasive wear,and the wear resistance is good.Due to the rapid quenching effect of plasma heating and cooling,the element segregation is effectively inhibited and the microstructure uniformity is improved,and the corrosion resistance of cladding layer is improved.The corrosion resistance is in the order of 304<AS1<A1 cladding layer.Finally,based on the high hardness and wear resistance of the AS1 cladding material,the feasibility of its application in the repair of sealing ring surfaces of construction machinery was explored.It was found that the hardness of the seal ring-AS1 melt clad layer is 721.3 HV,which is about twice the hardness of the seal ring base material and better than the hardness of the seal ring quenched layer;the wear resistance of the melt clad layer is 10 times that of the seal ring base material and about twice that of the seal ring quenched layer,and the main wear mechanism of the seal ring-AS 1 melt clad layer is abrasive wear;the surface inspection of the melt clad layer after grinding revealed no cracks,which meets the industrial safety production The surface of the clad layer was tested and found to be free of cracks and to meet the standards for safe industrial production. |
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