The Research On Wear And Corrosion Resistance Of Ni-based Coatings By In-situ TiC Reinforced

Plasma spray welding technology to prepare ceramic particle reinforced Ni-based coatings has become a hot spot in the industry because of its good wear and corrosion resistance.The problems such as coarse ceramic particles and easy to collect in the coatings lead to limited improvement effection.However,the fine and uniform ceramic particles generated in-situ can effectively solve these problems.In this paper,based on Ni60A self fluxing alloy powder,the alloy proportioning was optimized by doping Ti-Fe and Ti-Fe-Si multi-alloy powders to explore the synergistic effect of multi-alloy powders on the wear and corrosion resistance of Ni-based coatings.Finite element numerical simulation of temperature field in plasma spray welding process was carried out on ANSYS software to visualize the change of temperature field inside the coatings and to optimize the process parameter design of spray welding layer preparation.;the synergistic effect of Ti-Fe and Ti-Fe+Si powder on the microstructure of coatings were studied through OM?XRD?SEM?EDS,etc;the wear performance of coatings were studied through abrasive wear test;the electrochemical corrosion behavior of coatings were studied by electrochemical test.The results showed that:Based on the thermophysical parameters of Ni-based self fluxing alloy powder and 45 steel and plasma spray welding process,the secondary development was carried out by using APDL parametric language through ANSYS software with Gauss heat source model,which could clearly and intuitively carry out the change of temperature field with current during the spray welding of Ni-based alloy and realize the visualization of spray welding process.The welding speed was set at 80 mm/min,the swing speed of plasma arc in the x-axis direction was 1000mm/min,the swing width was 14 mm,the input voltage was 34 V and the input current was100¹45 A.The simulation results showed that,with the increased of current,the temper-ature of fusion zone directly corresponding to the center of arc column increases from 1168?to1673?.Meanwhile,when the input current was 130 A,the interface temperature of coating reacheed 1503?.The test results showed that,when the input current was 115¹30 A,the Ni-based coatings with good formability and macro performance could be obtained,which were consistent with the numerical simulation results of spray welding process,and further verifies the correctness of the theoretical analysis to prove the reliability of the simulation results.When preparing in-situ TiC-reinforced Ni-based coatings with Ni60A+Ti-Fe mixed powder,the coatings consisted of matrix phases FeNi₃??-Ni??-Ni₃Si?hard phases M₂₃C₆?M₇C₃?TiC,etc.With the addition of Ti-Fe powder,the high carbon M₇C₃ in the coatings structure decreased and the low carbon M₂₃C₆ increaseed;the in-situ TiC particle size was 1¹.5?m,dispersed in matrix or wrapped by M₂₃C₆ as heterogeneous nucleating element,could effectively refine grain size and improve wear and corrosion resistance of coatings.When the content of Ti-Fe was 6%,the micro-hardness reached 951 HV_0.2,which was 1.5 times of pure Ni-based coating;the wear weight loss rate was 0.63%,and the wear resistance was 3.8 times of pure Ni-based coating;the self-corrosion current was 1.250 x 10^-5 A,which was about 24.5%of pure Ni-based coating and the corrosion resistance was significantly improved.The dispersion of TiC and other ceramic phases in the caotings in the matrix effectively hinders the electron migration during the corrosion process and significantly reduces the self-corrosion rate.At the same time,compared with metal materials,ceramic particles have higher equi-librium potential.The higher the content of ceramic particles,the higher the self-equilibrium potential of the material and the lower self-corrosion tendency.In-situ TiC-reinforced Ni-based coatings were prepared by using Ni60A+Ti-Fe+Si mixed powder.When the content of Ti-Fe and Si powder were both 6%,a better coating with better process performance and structure could be obtained.Compared with the single doped Ti-Fe,the matrix structure of the coatings had little change,but due to the addition of Si powder,the phase formation of TiSi₂?SiC and Ti₃SiC₂ in the coatings also promoted the increase of the content of?-Ni₃Si;the middle and top structure of the coatings were quite different,there were more honeycomb-like eutectic structure of"?-Ni+?-Ni₃Si"in the middle matrix and bread-like"FeNi₃+Ti₃SiC₂"mixed structure.Mosaic between the eutectic structure;in the top area,more TiSi₂?SiC and other ceramic phases were produced,and the higher the content of Si powder,the greater the amount of formation.At the top of the coatings,the micro-hardness increased with the addition of Si powder;when the content of Si powder was 6%,the micro-hardness of the top of the spray-welded layer could reached 987 HV_0.2,in the middle of the coating,the opposite tendency occurs.The in-situ TiC-reinforced Ni-based coating synergis-tically prepared by Ti-Fe+Si had about 79%wear resistance compared with that of the direct single-doped Ti-Fe powder,but its corrosion resistance was comparable to that of the latter.The formation mechanism of?-Ni₃Si and Ti₃SiC₂ and their influence on wear resistance need further study.