| Hydraulic column plays the significant role in supporting and bearing the pressure of the coal seam.However,the harsh environment in the mine have seriously damaged the usage of hydraulic column,corroding the surface of the hydraulic column and making them unusable.Therefore,the surface of the column surface has to be treated before using.Traditional surface treatment methods are electroplating,electroless plating and laser cladding.However,the former method is easy to produce electroplating waste water,which contains heavy metal ions and all kinds of acid mist exhaust,seriously polluting environmental.And the manufacture of laser cladding alloy powder is costly and difficult,also it will increase the air suspended particles.So,in this paper,it puts forward a new method to deal with the pillar surface,by using laser welding instead of laser cladding,thin strip instead of powder.In this paper,high-entropy alloy AlCoCrFeNi and 27 SiMn steels have been studied,which is welded by single channel laser lap welding and multi-channel laser lap welding.The influence of solidification mode,process parameters on the welding seam,and the mechanical properties,wear resistance and corrosion resistance of prepared laser remelting layers have been investigated using the optical microscope,scanning electron microscope,X-ray diffraction analyze,integrated test system of nanomechanics,wear tester and electrochemical test station.The obtained results are shown as follows: AlCoCrFeNi high-entropy alloy is mainly composed of single-phase BCC structure solid solution.Its microstructure is large equiaxed crystals with petal-like polygonal dendritic structure inside the equiaxed crystals.The structure of the weld center of 27 SiMn steel is lath martensite and retained austenite.A good metallurgical bonding was obtained by single pass laser overlap welding of the two materials.The structure of the transition zone is columnar dendrite at the edge of the high-entropy alloy AlCoCrFeNi weld,equiaxed dendrite at the center and lath martensite formed by martensite transformation in 27 SiMn.The average microhardness of high-entropy alloy AlCoCrFeNi base metal is 543.2±3.4 HV,the average microhardness of weld metal is 626.1±2.7 HV,the average microhardness of 27 SiMn steel base metal is 263.2±4.2 HV,and the average microhardness of weld metal is 386.9±6.8 HV.In the condition of different laser power and welding speed,it can obtain smooth,compact and defect-free welds.With the increase of laser power,weld penetration,weld width and microhardness increase,while the waist height and waist width change little.With the increase of welding speed,the weld penetration,weld width,waist height and waist width decrease,and the microhardness also decreases but does not change much.The influence of laser power on penetration is more obvious,and the influence of welding speed on fusion width,beam waist height and beam waist width is more obvious.In the condition of different laser power and welding speed,it can obtain good-quality welding composite layer.The yield strength of the welding compound layer is higher than that of parent metal,which are 608.08±36.24 MPa and 482.38±19.62 MPa,respectively.The friction coefficient of the welding compound layer is less than that of the as-cast base metal.The wear amount of the composite layer is closely related to its surface hardness.When the hardness is higher,the wear amount is smaller.The wear amount of welding compound layer is lower that of parent metal,which are 7.65±0.32 mg and 8.62±0.41 mg,respectively.The wear mechanism is dominated by adhesive wear and abrasive wear.The self-corrosion potential of the welding compound layer is higher than that of the base metal,and its self-corrosion current density is lower,which indicates that the corrosion resistance of the welding compound layer is slightly better than that of the high-entropy alloy AlCoCrFeNi base metal. |
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