| As a high-strength and corrosion-resistant surface modification material,high-entropy alloy coating has broad application prospects in improving the performance,prolonging the service life and reducing the loss of marine engineering steel.Plasma cladding and laser cladding technology is scalable and efficient for preparing high entropy alloy coating.It is necessary to carry out systematic researches on regulating synthesizing methods,understanding the microstructure formation rule and even deeply analyzing the properties of high-entropy coatings on marine engineering steel.At the same time,reducing the cost of coatings and simultaneously ensuring their comprehensive performance has more commercial value.In this paper,FeCrMnNi（Co/Al）high-entropy alloy coatings were prepared on the surface of E32 marine steel by plasma and laser cladding technology,respectively.The aim is to promote the strength and corrosion-resistant of E32 marine steel by enhancing bonding strength between coating and substrate.The main results are as follows:（1）FeCrMnNiCo high-entropy alloy coatings were prepared by plasma cladding technology at cladding currents of 115 A and 133 A.The results show that the FeCrMnNiCo high entropy alloy coating is composed of single FCC phase with typical dendritic microstructure on the longitudinal section,which is almost not affected by the cladding current.When the cladding current is 115 A,the hardness of the coating is 140.4 HV0.5,while the self-corrosion potential and the self-corrosion current density is-0.19 V and4.15×10-7 A·cm2,respectively.With the increase of cladding current,the grain size of the coating increases and the average hardness decreases to about 135.4 HV0.5.As expected,the grain boundary corrosion is weakened and corrosion resistance of the coating is enhanced along with grain growth,which may originate from the decrease of grain boundaries.The higher the Fe content in the region closer to the substrate,the lower the passivation element content and the weaker the corrosion resistance.（2）The FeCrMnNiAl high-entropy alloy coating was prepared by the same plasma cladding process parameters.The structure,microstructure and properties of the coating were investigated when Al element replaced Co.The results show that the structure of powder and coating is BCC.The microstructure is irregular columnar crystal morphology,which evolves into columnar crystal and coarse equiaxed crystal with the increase of cladding current.The hardness of the coating is 418.5 HV0.5 at 115 A cladding current,Much higher than FCC structural FeCrMnNiCo coating.However,the corrosion resistance of FeCrMnNiAl coating is weaker than that of FeCrMnNiCo coating under the same conditions.From the coating surface to the substrate,the hardness of the coating increases first and then decreases,and the corrosion resistance of the coating decreases with the increase of Fe content in the coating.（3）Based on laser cladding technology,the effects of cladding layers on the microstructure,structure and properties of FeCrMnNi（Co/Al）high entropy alloy coatings were studied.The results show that the surface of the coating prepared by laser cladding technology is rough and thin.Meanwhile,there is no thermal deformation occurring on the substrate.Because the laser spot diameter is smaller and energy is more concentrated than the plasma beam diameter,the matrix dilution effect is more serious,which induces great changes of phase structure.For the FeCrMnNiCo coating,the single-layer FeCrMnNiCo coating exhibits a BCC+FCC dual-phase mixed structure,and the phase structure transformation leads to the increase of hardness to 339.6 HV0.5.Tthe self-corrosion current density of single layer FeCrMnNiCo coating is 3.01×10-6 A·cm2 due to the galvanic corrosion between different phases.With the increase of the number of cladding layers,the content of FCC phase increases,while the hardness and corrosion resistance of the coating decreases,simultanueously.For the FeCrMnNiAl coating,the single-layer coating exhibits a dual-phase（BCC+σ）structure with high hardness(362.5 HV0.5)and enhanced self-corrosion current density,i(3.71×10-6 A·cm2).Noteworthy,theσphaseand hardness increases apparently,but the corrosion resistance decreases,along with increasing the cladding layers.Plasma and laser cladding are effective methods to prepare high-entropy alloy coatings on the surface of marine steel,and the corrosion resistance of the coatings is much better than that of the substrate.At the same time,except the FeCrMnNiCo coating prepared by plasma cladding,the hardness of other coatings is higher than that of the substrate. |
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