Tribological Characterization Of High Entropy Alloy Gradient Coating On Friction Subsurface Of Plunger Pump By Laser Cladding

The plunger vice is the key friction vice of the plunger pump when the plunger pump is applied in the seawater environment,because the marine environment contains a large number of sand particles and seawater itself with the corrosive properties of the plunger vice surface of serious wear and tear at the same time the outer surface will also occur electrochemical corrosion,in the corrosion and wear interaction,will accelerate the failure of the plunger,resulting in the plunger pump in the seawater leakage,affecting the efficiency of the plunger pump and Service life.By reading the literature and reviewing the data,we found that the preparation of a layer of metal protective coating on the surface of the plunger using laser melting technology is a very effective method.In this paper,three kinds of alloy coatings,FeCoCrNi Cu_0.3,FeCoCrNi Al Cu_0.3 and FeCoCrNi Ti Cu_0.3,were prepared by Laser cladding technique based on the commonly used FeCoCrNi alloy system with a small amount of Cu elements,followed by the addition of Ti and Al elements,respectively,to study the effects of the addition of Ti and Al elements on the high-entropy alloy coatings.The effects of adding Ti and Al elements on the microstructure,phase structure,microhardness,wear resistance and corrosion resistance of the alloy coatings were investigated.Subsequently,the high-entropy alloy coatings were prepared based on continued experiments using Laser cladding technology for multi-layer and multi-pass,and additive materials manufactured the high-entropy alloy gradient coatings and the evolution of their microstructure and their microhardness were investigated.Finally,the static and dynamic simulations of the untreated plunger and the plunger with gradient coating were carried out using Ansys simulation analysis software.The specific results of the study are as follows:Three high-entropy alloy coatings,FeCoCrNi Cu_0.3,FeCoCrNi Al Cu_0.3,and FeCoCrNi Ti Cu_0.3,were prepared on 38Cr Mo Al substrate by laser melting technique with suitable processing parameters.FeCoCrNi Al Cu_0.3 showed the highest microhardness of 683.5HV_0.3.The thickness of all three coatings was about 1 mm,and the coatings achieved good metallurgical bonding with the substrate,with dense structure and no defects such as cracks and porosity,which ensured the excellent bonding of the coatings.The microstructure of the coating is from the bonding surface to the surface with plane crystals,columnar crystals,dendrites,and equiaxed crystals,and the grains are refined to a certain extent with the addition of Ti and Al elements.After the addition of the Al element,the main diffraction peak of the coating phase structure changed to the BCC phase.The electrochemical tests showed that FeCoCrNi Al Cu_0.3 exhibited a higher self-corrosion potential and a minimum corrosion current density,which indicated that it had better corrosion resistance.Subsequently,neutral salt spray tests were conducted to further test the corrosion resistance of the alloy coating for168h,360h,and 720h.The neutral salt spray test results further proved that FeCoCrNi Al Cu_0.3has better corrosion resistance.Under the dry friction test,FeCoCrNi Al Cu_0.3 showed better wear resistance as well as minimal friction coefficient.Based on the dry friction test,a saturated Na Cl solution was selected as the medium,and the temperatures were chosen as room temperature and 50°C.The friction coefficient of the coating showed a significant decrease under the lubrication effect of the solution,and the FeCoCrNi Al Cu_0.3 coating still showed better wear resistance.FeNi alloy,FeCoCrNi,FeCoCrNi Cu_0.3,and FeCoCrNi Al Cu_0.3 were selected as the materials for each layer of the gradient coating,and multilayer and multichannel laser cladding technology was chosen as the preparation method.The EDS line scan analysis of the element distribution indicates that the design of the gradient coating is reasonable,and a certain degree of diffusion penetration between the elements is observed,proving that the gradient coating achieves good metallurgical bonding.The microstructure of the gradient coating is in the order of plane crystals,columnar crystals,dendrites and equiaxial crystals from the bond between the coating and the substrate.Very obvious remelting lines are observed.The grain size in the remelted area grew up to a certain extent,with columnar crystals,dendrites to equiaxial crystals above the remelting line,and no fine equiaxial grains below,and the microstructure of the entire gradient material shows such periodic changes.The microhardness of the gradient material also shows an obvious gradient change from282HV_0.3 at the bottom to 678HV_0.3 at the surface.In hydrostatic simulation analysis,it was found that the maximum stress value of the untreated plunger and the plunger with gradient coating were concentrated at the contact between the plunger and the plunger head when they were subjected to a certain degree of static pressure.Still,after observing the maximum deformation and the maximum stress value,it was found that the maximum stress value of the plunger with gradient coating was significantly reduced by 28.1%.The maximum deformation was reduced by 19.6%.The kinetic simulation results showed that the gradient coating on the plunger surface could effectively improve the stress distribution on the plunger surface during the reciprocating motion.The observation of the stress-strain cloud showed that the plunger with the gradient material was also improved in terms of strain resistance,which was 27%higher than before the treatment and 13%higher than before the treatment.In summary,combined with the results of physical experiments and simulation analysis,the preparation of high-entropy alloy gradient coating on the plunger surface by laser additive manufacturing technology can significantly improve the performance of the plunger and increase the service life of the plunger pump.