Study On Preparation And Properties Of Laser Cladding CoCrFeNi-X High Entropy Alloy Coatings

As a new type of alloy material,high-entropy alloy has a simple crystal structure and outstanding performance.In order to meet the performance requirements of materials under different conditions,the regulation and optimization of the properties of high-entropy alloys has gradually become a research hotspot.In this study,different high-entropy alloy coatings were prepared for different service environments of 304LN stainless steel(steel for marine transport ships),42CrMo(steel for marine port rails),and 00Cr13Ni4Mo stainless steel(steel for water turbine blades)to improve the surface properties of the materials.The specific research content is as follows:CoCrFeNiTi_x(x=0,0.25,0.5,0.75,1.0)high-entropy alloy coatings were prepared on the surface of 304LN stainless steel,and the effect of the atomic ratio of Tion the microstructure and properties of the coatings were studied;In addition,the CoCrFeNiTihigh-entropy alloy coating with the best overall properties was doped with different proportions of TiC ceramic phase(10wt%,15wt%,20wt%)to explore the effect of TiC ceramics on the microstructure and properties of the CoCrFeNiTihigh-entropy alloy coating.The surface strengthening methods of laser cladding high-entropy alloy,laser quenching and laser alloying were used on the surface of 42CrMo steel,and the effects of the three strengthening methods on the hardness,wear resistance and corrosion resistance of 42CrMo steel were compared.The CoCrFeNi-X(Al,Mn,Mo)high-entropy alloy coatings were prepared by laser cladding on the surface of 00Cr13Ni4Mo stainless steel,and the effect of the addition of Al?Mn?Mo elements on the wear resistance and corrosion resistance(electrochemical corrosion?cavitation corrosion)of the CoCrFeNiseries high-entropy alloy coating was studied.The research results show that the microhardness of the CoCrFeNiTi_xhigh-entropy alloy coatings gradually increase with the increase in the proportion of Tiatoms.The microhardness of the CoCrFeNiTihigh-entropy alloy coating is as high as 641HV,which is about 3.2 times that of the substrate.The wear resistance also increases with the increase in the proportion of Tiatoms,and the mass loss per unit time of the CoCrFeNiTihigh-entropy alloy coating is only 0.4 of that of the substrate.The results of electrochemical experiments show that with the increase of the proportion of Tiatoms,the self-corrosion current density of the high-entropy alloy coatings gradually decrease,the overpassivation potential gradually increase,and the corrosion resistance of the coatings gradually increase.In the CoCrFeNiTihigh-entropy alloy coating with different proportions of TiC ceramic phase,it is found that the high-entropy alloy coatings with 10wt%and 15wt%TiC can significantly improve the surface hardness,wear resistance and corrosion resistance of the material.However,when the addition amount of TiC increases to20wt%,a large number of agglomerated TiC ceramic particles appear in the high-entropy alloy coating,and the surface hardness,wear resistance,and corrosion resistance of the material decrease instead.The 42CrMo steel has three different strengthening layers prepared by three different surface strengthening methods.The experimental results show that laser alloying and laser quenching make the coating have higher surface hardness(915HV,854HV)and wear resistance.However,its self-corrosion current density in 3.5%Na Cl solution is 1-2 orders of magnitude higher than that of the substrate,showing poor corrosion resistance.The high-entropy alloy coating not only has higher surface hardness(652HV)and wear resistance,but also its self-corrosion current density is one order of magnitude lower than that of the substrate,showing excellent corrosion resistance.The CoCrFeNi-X(Al,Mn,Mo)high-entropy alloy coatings were prepared on the surface of 00Cr13Ni4Mo.The experimental results show that the CoCrFeNiMo high-entropy alloy coating has the highest surface hardness(689HV),wear resistance,and electrochemical corrosion resistance.The 40 hours cavitation experiment results show that the high-entropy alloy coatings can significantly improve the cavitation corrosion performance of the substrate material,and the mass loss of the AlCoCrFeNiand CoCrFeNiMo high-entropy alloy coating is only 0.24 and 0.13 of the substrate.