Study On Microstructure And Properties Of FeAlCuCrNiMo_xNb_yTi_z High-entropy Alloy Surfacing Layer

Nowadays,in the era of rapid development of manufacturing industry,more and more energy is consumed due to wear and corrosion.In order to prepare the surface materials of mechanical parts with high hardness,high wear resistance and high corrosion resistance,FeAlCuCrNiMo_xNb_yTi_z high-entropy alloys surfacing layer（x,y,z=0.2,0.6,0.8;x,y,z are molar ratios）was prepared on the surface of carbon steel by the gas metal arc welding technique.The L₉（3⁴）orthogonal table was used to carry out the orthogonal test design for the three trace alloy elements Mo,Nb and Ti,and the content ratio was changed.The FeAlCuCrNiMo_xNb_yTi_z was tested by microhardness test,abrasive wear test and electrochemical corrosion.The structure and properties of the high-entropy alloy surfacing layer were studied,and finally the optimal alloy element composition ratio of wear resistance and corrosion resistance was determined.The main conclusions are as follows:（1）Combined with the calculation of parameters such as mixed entropy(ΔS_mix),enthalpy of mixing(ΔH_mix),atomic size difference（δ）,valence electron concentration（VEC）of multi-component alloys,it is found that FeAlCuCrNiMo_xNb_yTi_z high-entropy alloys easily forms solid solution phase BCC and FCC coexist.Combined with XRD detection and analysis,the phase composition of the FeAlCuCrNiMo_xNb_yTi_z high-entropy alloys surfacing layer is mainly a large amount of Fe-Cr phase and a small amount of MC,and even the Laves phase will appear.（2）Through scanning electron microscopy analysis,the structure of the FeAlCuCrNi-Mo_xNb_yTi_z high-entropy alloys overlay layer exhibits a typical dendrite structure,which is composed of gray dendrites（DR）and white interdendrite（ID）structures.The precipitated hard（Nb,Ti）C composite carbides are dispersed in the structure.In addition,there are a large number of cellular eutectic Fe₂（Nb,Ti）composite Laves in the structure of the FeAlCuCrNiMo_0.2Nb_0.8Ti_0.8 overlay layer.Phase precipitation,microstructure and energy spectrum analysis can verify this result.（3）The microhardness of FeAlCuCrNiMo_xNb_yTi_z high-entropy alloys surfacing layer can be up to 700 HV,and the hardness is more than 3 times that of the base metal.Adding Mo,Nb,Ti to the wear resistance of high-entropy alloys surfacing layer the performance has been significantly improved,and the optimization effect is:Nb>Ti>Mo,of which FeAlCuCrNiMo_0.2Nb_0.8Ti_0.8 high-entropy alloys surfacing layer has the highest microhard-ness,while the texture grains of the surfacing layer are the smallest,The grain boundary is the most,the precipitated Fe₂（Nb,Ti）composite Laves phase is the most,and the grain refining effect is the most significant.Simultaneously,the furrow of the surfacing layer structure is the shallowest,relatively flat,without abrasion and flaking,lost due to abrasion The quality is also the smallest and the wear resistance is the best.The FeAlCuCrNiMo_xNb_y-Ti_z high-entropy alloys surfacing layer has higher microhardness and good wear resistance,mainly due to the combined effect of solid solution strengthening,grain boundary strengthening,fine grain strengthening,and second phase precipitation strengthening.（4）The corrosion resistance of FeAlCuCrNiMo_xNb_yTi_z high-entropy alloys surfacing layer is better than that of 304 stainless steel.304 stainless steel has a higher self-corrosion current density,a smaller arc resistance radius,and more corrosion in corrosion morphology.Pit,the electrochemical corrosion rate is faster;and the FeAlCuCrNiMo_xNb_yTi_z high-entropy alloys surfacing layer exhibits low self-corrosion current density,high self-corrosion potential,wide passivation interval,and a large arc resistance radius.Adding Mo,Nb,Ti improves the corrosion resistance of high-entropy alloys surfacing,and the optimization effect is:Mo>Ti>Nb,of which FeAlCuCrNiMo_0.8Nb_0.2Ti_0.8 high-entropy alloy surfacing layer has the slowest corrosion rate The corrosion resistance effect is the best.This is because the simple solid solution structure of the high-entropy alloy is relatively single,and the BCC structure is the most in the structure of the surfacing layer.The BCC structure is a solid solution based on the Fe-Cr phase.The more Cr elements,The better the corrosion resistance of the surfacing layer,so the FeAlCuCrNiMo_0.8Nb_0.2Ti_0.8 high-entropy alloy surfacing layer has the best corrosion resistance.