| In this paper,the Al0.1CoCrFeNi high-entropy alloy coating was prepared on the surface of H13 steel substrate by means of laser cladding technology,using simultaneous powder feeding method and preset method respectively.The effects of process parameters such as laser power,scanning speed,and powder feeding voltage on the macroscopic morphology and microstructure of the coating were studied.Through the analysis of coating performance,the best process parameters were selected and the lap method was used for large area preparation.The corrosion resistance and wear resistance of the coating at normal temperature,high temperature oxidation resistance and thermal shock performance were analyzed.The corrosion resistance,wear resistance,thermal shock resistance and oxidation resistance mechanism of the coating were studied.Tests show that the best process parameters for the coating preparation by synchronous powder feeding method are laser power 1200W,scanning speed 1mm/s,powder feeding voltage 10V,preset method is laser power 1800W,scanning speed 1mm/s.Both of the upper and middle structures of the coatings are dense equiaxed crystals,and the bottoms are columnar crystals with obvious growth trends.The surface of the coatings prepared by the synchronous method is relatively flat,with a minimum dilution rate of 28.66%and a maximum hardness of 789.93HV,preset coating is higher,the lowest dilution rate is 21.21%,and the highest hardness is 871.82HV.The large-area preparation was performed at an overlap rate of 30%,the coating was flat and the compact microstructure was obtained without defects.The Fe-Cr phase is similar to the substrate can be found in the coating with lower heat input.When the laser power is 900W,the scanning speed is 1mm/s or the laser power is not higher than 1300W,and the scanning speed is 2mm/s,the coating phase is mainly composed of FCC+BCC phase,otherwise the others is composed of FCC Phase and disordered FCC phase,overlapping samples are similar to single-pass samples.The optimal process parameters are determined by hardness and dilution rate,and are supported by electrochemical performance testing.It was found that the coatings prepared with the best process parameters had lower corrosion current density and higher corrosion potential,which were 5.50×10-7A/cm2 and-0.59V,respectively.With the increase of the dilution rate,the coating corrosion became more serious.The corrosion current and corrosion potential of the pre-formed coating are 2.24×10-7A/cm2 and-0.36V,compared to the synchronous coating current,which is 3.26×10-7A/cm2 lower,and the potential is increased by 0.23V.Decreased,better corrosion resistance,and both are significantly better than the substrate.Under the same load,the coating has better wear resistance than the substrate.When the load increases,the friction and wear coefficient decreases,and the volume wear rate increases.Under the loads of 5N,10N,and 15N,the friction and wear coefficients of the preformed coatings are 0.46,0.43,and 0.37,and the volume wear rates are 3.35×10-6mm3/(N·m),10.96×10-6 mm3/(N·m),25.52×10-6 mm3/(N·m),compared with the synchronous coating,they were reduced by 5.37%,14.38%,and 34.88%,respectively.The coating and substrate wear mechanisms are the combination of oxidative and adhesive wear.The thermal shock tests were performed at temperatures of 600?,800?,and1000?.It was found that the coating is firmly bonded to the substrate,can withstand multiple thermal shocks without cracks,and the substrate cracks after cycling at 1000? for 7 times.The thermal shock resistance of the coating is superior to that of the substrate.Oxidation experiments shows that the coating and substrate were barely oxidized at 600?.After oxidation at 800?for different durations,non-dense scales such as Fe2O3 and CoFe2O4appear preferentially in the coating.At the same time of oxidation,the weight gain of the coating is lower,and the coating has better oxidation resistance than the substrate. |
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