| High entropy alloys(HEAs)are generally composed of 5 to 13 elements,and the molar percentage of each element is between 5%and 35%.High entropy alloy is an ideal coating materials which has excellent properties on strength hardness and wear resistance.FeCoNiCrxAl(x=1,1.5,2,2.5)and ceramic particles reinforced FeCoNiCri.sAl HEAs cladding coatings were produced by laser cladding processing on the surface of Q345 mild steel.The phase and microstructure of the cladding coatings were characterized by SEM,XRD.The corrosion resistance was tested by electrochemical workstation.The wear property was tested by friction and wear equipment.The experiment of laser cladding technology was carried out on the substrate of Q345 mild steel,and the parameters were optimized in the text.The results showed that with the increase of laser power,the depth and dilution ratio of the cladding coatings increased at certain conditions of other process parameters.With the increase of laser scanning speed,The height and depth of the cladding coatings decreas.With the increase of powder feeding rate,the cladding height increases,but the depth and dilution ratio decreases;with the increase of overlap ratio,the width and thickness of cladding coatings decrease.furthermore,the dilution ratio also decreases.The well-formed and defect-free(such as porosity and cracking)cladding caotings can be obtained while the laser parameters are laser power 1600 W,laser scanning speed 8mm/s,powder feeding 7.5 g/min and overlap ratio 50%.The cladding coatings of FeCoNiCrxAl(x=1,1.5,2,2.5)prepared by laser cladding have typical equiaxed grain structure and single BCC structure.The results of electrochemical test showed that the corrosion resistance of the cladding coating is greatly improved compared with Q345.With the increase of Cr mole fraction,the corrosion resistance of the cladding coating increases firstly and then decreases.While mole fraction of Cr is 1.5,the coating has the best corrosion potential and lowest corrosion current,and the lowest corrosion rate.It implied that the cladding coating with 1.5 mol Cr possessed the best corrosion resistance.With the increase of Cr content,the hardness of cladding coating increases,however,the friction coefficient of the coatings decreases.As the result,the cladding coatings had higher wear resistance than that of substrate of Q345 steel.The TiC ceramic particles in the cladding coating are mainly in the form of small particles,petals and fishbones.The small granular and fishbone-like granules were formed.By means of non-heterogeneous nucleation mechanism.But the petaloid granules were formed by heterogeneous nucleation.With the addition of Ti Element,the lattice distortion increases and the lattice constant of cladding coating increases.The cladding coating phase structure consist of BCC1、BCC2and TiC.The micro-hardness of the cladding coating increases from 550 HV0.2 to 810 HV0.2 with the introduction of ceramic particles.With the increase of the hardness of the cladding coating,the friction coefficient of the cladding coating decreases.Under the same friction and wear condition,the wear loss of the cladding coating is reduced by half,and the wear resistance of the cladding coating is improved effectively. |
